Coolant temps tell you how hot your engine is running. When you tow, the engine makes more heat, so the coolant temperature helps you see if the cooling system is keeping up.
Term
coolant temp going down the road
This is about what your engine temperature does while you’re driving normally. A good cooling system should keep the temperature fairly steady instead of letting it climb.
Your thermostat is like a heat gate for the engine coolant. It decides when coolant should start flowing through the radiator to cool the engine down.
Term
sensor or your gauge
Your truck uses a sensor to measure temperature and a gauge to show it to you. On some older trucks, the gauge can be off, so it may not match the real temperature.
An infrared temp gun is a tool that measures temperature from a distance. It can help you double-check whether something is really overheating, but it’s not perfect—where you point it matters.
A radar gun is usually for measuring speed. Here, the host is basically saying: if your truck’s temperature gauge seems weird, use a different tool to confirm what the temperature really is.
The radiator cap is like a pressure regulator for the cooling system. It lets the coolant stay liquid at higher temperatures by allowing the system to run under pressure.
Pressurizing the coolant makes it boil at a higher temperature. That helps the engine stay cooler and reduces the risk of overheating from coolant boiling.
Your radiator cap controls how much pressure the cooling system runs at. More pressure makes the coolant boil at a higher temperature, so the engine is less likely to overheat.
Overheating means the engine is getting hotter than the cooling system can handle. It’s more likely when you’re towing heavy, driving in extreme heat, or when the cooling system isn’t as effective as it used to be.
“Gross” means the total weight the truck is carrying, including the trailer and everything in it. If you’re near the truck’s maximum total weight, the engine and cooling system have to work much harder.
Death Valley is extremely hot, so your engine cooling system has a harder time getting rid of heat. That’s why overheating problems show up there more easily than in cooler places.
Boost is how much extra air pressure the turbo is forcing into the engine. When boost is higher than normal, the engine is working harder, which can lead to higher temperatures.
A dyno event is when vehicles are tested on a dynamometer, which measures output like horsepower and torque under controlled conditions. It’s useful for comparing setups (tuning, fueling, turbo performance) and diagnosing issues—especially when you’re seeing high EGTs or boost while towing.
The Renault Wind is a small car with a focus on open-air driving. When there’s a strong headwind, it can make the car work harder to keep moving at the same speed. That can affect how efficiently it uses energy or how it feels on the road.
Term
parasail
He’s comparing the setup to a parasail—something that catches the wind. When the wind catches your trailer/load like that, the truck has to work much harder and can run hotter.
Term
open deck trailer
An open deck trailer is a flatbed-style trailer with an exposed deck rather than a fully enclosed box. Trailer design affects airflow and towing resistance, which can change how much heat the truck has to manage—particularly in strong wind or on grades.
A headwind is wind hitting the front of your truck. It can change how well the truck cools itself, which can make coolant temperatures run higher or lower.
If trailer brakes are dragging, the trailer is braking even when you’re not asking it to. That makes the truck work harder and can lead to overheating while towing.
Steady state means you’re basically driving the same way without big changes—like cruising at a constant speed. In that situation, coolant temperature should behave predictably if the cooling system is healthy.
Coolant buildup means the coolant temperature is getting too hot. This often happens when there isn’t enough airflow to cool the radiator, like in extreme heat or slow stop-and-go driving.
A mechanical fan clutch is a cooling-fan controller that engages based on temperature. As the engine gets hotter, it helps the fan spin more to pull air through the radiator.
An electronic fan clutch is a cooling-fan controller that uses sensors and computer control. It can turn the fan on harder when the engine needs cooling, like during towing or hot traffic.
“12 valve” is a way of describing an older diesel engine design based on how many valves it has. Different engine generations can behave differently when it comes to cooling, so the advice about the fan and temperatures is aimed at that specific type of diesel.
“24 valve” is another diesel engine design label based on how many valves the engine has. The host mentions it because these engines can show overheating symptoms in a similar way when the cooling fan isn’t engaging properly.
Electric fans are cooling fans powered by a motor instead of being spun by the engine. The host’s point is that on some diesel trucks, the original mechanical fan system is already doing the job it was designed for, so an electric-fan swap may not fix overheating by itself.
Term
electronic truck
Here, “electronic truck” means a newer diesel truck with computer-controlled systems. The host is saying the cooling-fan diagnosis can be different on newer trucks, because the fan may be controlled by electronics and sensors.
The harmonic balancer is a part on the engine’s crankshaft that helps smooth out vibrations. If it gets damaged, it can lead to bigger problems and even hurt other parts nearby.
Term
hard clutch cut
A hard clutch cut sounds like a clutch-related action that happens suddenly instead of smoothly. Here it’s mentioned as something that got snagged and caused damage.
A mechanical override is a fail-safe that makes the system act on its own when things get hot enough. It’s like a backup so the engine still gets cooling even if the computer strategy isn’t doing it.
The water pump is what actually pushes coolant around the engine and cooling system. If the coolant is being routed the wrong way, the pump can still be moving fluid, but the engine may not get cooled effectively.
A bypass is an alternate route coolant can take. Instead of going through the radiator, it can keep coolant moving through the engine so you don’t get areas that overheat while the thermostat is still closed.
Stagnant water means coolant that isn’t moving where it needs to. If coolant doesn’t circulate, parts of the engine can heat up much faster and create hot spots.
Hot spots are parts of the engine that get hotter than the rest. They can happen when coolant isn’t flowing correctly, so those areas don’t get cooled as effectively.
Recirculation means coolant is being sent back around instead of going through the radiator. If that loop isn’t working the way it should, the engine may not cool properly.
Gates is a company that makes aftermarket car parts, including thermostats. The host is saying some cheaper thermostats (like Gates) may not work as well as the original-style Cummins ones.
NAPA sells aftermarket parts, including thermostats. The host is grouping it with other cheaper thermostat options that may not perform as reliably as the genuine Cummins part.
Cummins makes a lot of diesel engines used in trucks. The host is saying the original Cummins thermostat is better than cheap replacements because it’s designed to open properly and last longer.
“205 degrees” is the temperature where the thermostat is supposed to start working. It affects when coolant begins circulating to keep the engine at the right temperature.
“Cooling system issues” means your truck isn’t managing engine heat correctly. The host is saying that strange temperature behavior is often caused by the thermostat.
Most trucks don’t run pure antifreeze or pure water—they use a mix. That mix helps prevent freezing and overheating, and it also helps protect the cooling system from corrosion.
Surface tension is how “sticky” a liquid’s surface is. If the coolant spreads and wets the radiator better, it can pick up and move heat more effectively.
Ethylene glycol is the antifreeze ingredient in most coolant mixes. It helps keep the coolant from freezing and helps it handle heat better, but it’s not the same as water for cooling.
“Water wetter” is an additive that’s meant to help coolant spread out and contact the radiator surfaces better. That can help the engine shed heat more effectively.
“VP truck” is an enthusiast shorthand for an older diesel configuration with a specific fuel-injection pump type. The host is saying those trucks can get oily grime around the radiator that blocks airflow and cooling.
A breather is a vent that lets engine vapors escape. If it’s positioned so oil mist gets blown toward the radiator, it can make the radiator dirty and less effective.
Operating temperature is the normal “working range” your engine is supposed to be at. If the engine behaves differently than expected, it can point to a cooling problem.
An aftermarket radiator is a replacement cooling part made by a company other than the truck’s maker. Some are better at cooling, but you can’t assume “new” automatically means “much better.”
“Four core” describes the radiator’s internal construction—multiple rows/passes of cooling material that increase heat-transfer area. A “copper core” indicates the heat-exchanging material is copper, which is commonly used because of its strong thermal conductivity.
Cooling capacity is how much heat the radiator can handle. If the new radiator doesn’t really increase that ability—or if the system is still clogged—overheating can continue.
Mineral deposits (like calcium scale) can build up inside the radiator and cooling passages. That buildup blocks flow and makes it harder for the radiator to cool the engine.
Vinegar is used as a mild acid to dissolve mineral buildup inside the radiator. Afterward, you should flush everything out so the vinegar doesn’t stay in the cooling system.
Term
flushed it a bunch
Flushing means running clean fluid through the cooling system and draining it out to remove the cleaning stuff and debris. It’s important so leftover cleaner doesn’t cause new problems.
Hydrochloric acid is a very strong cleaning chemical. It can remove buildup, but it can also eat away at metal parts if it’s too strong or used the wrong way.
A radiator flush is like cleaning out the cooling system with a special cleaner. It’s meant to remove gunk so coolant can flow better, but you don’t want to use harsh chemicals that could hurt the radiator or heater parts.
A fan clutch controls how strongly the cooling fan pulls air through the radiator. If it doesn’t engage properly, the radiator won’t get enough airflow to cool the engine.
The fan shroud is a piece that helps guide air through the radiator. Without it, the fan can move air around the radiator instead of through it, so the engine may run hot.
An orifice is basically a restriction in the coolant path. A smaller restriction makes coolant flow differently than a larger one, so using the wrong fitting size can reduce or redirect cooling and contribute to overheating.
BTU is a unit that measures how much heat something can move or produce. Here, the speaker is saying the heater can dump extra heat into the cabin, which can help the engine run cooler in extreme conditions.
A ball valve is a simple on/off valve. In this context, closing it stops coolant from going through the heater core, which can reduce unwanted heat transfer.
Your cooling system is what keeps the engine from getting too hot. It uses coolant and airflow to move heat away—if parts are clogged or airflow is poor, overheating can happen.
A fan shroud is like a cover that helps the fan push air through the radiator instead of letting it spill around. If it’s missing or damaged, the engine may not cool as well.
A ducted fan is a fan that’s “guided” so the air goes where you want it. With a shroud, more of the fan’s airflow actually passes through the radiator.
Fan blades are what physically push air through the radiator. If they’re damaged or not the right size, the fan may not move enough air to keep the engine cool.
A blown head gasket is a serious engine sealing failure. It can cause coolant to get overheated fast, and you may see signs like soot or gunk when you inspect the cooling system.
A freeze plug is a small plug in the engine block that seals coolant channels. If the engine gets too hot or coolant conditions aren’t right, that plug can pop out. People sometimes change coolant routing to prevent that kind of failure.
Coolant passages are the internal pathways inside the engine where coolant flows to carry heat away. Where coolant goes (and how it flows) affects which parts get cooled the most. If the passages are already designed to move coolant well, extra routing may not help as much as people think.
The engine block is the big metal body of the engine that holds the cylinders and coolant channels. How coolant moves through it affects how hot different cylinders get.
Head flow is how well the engine’s cylinder head passages let air and exhaust gases move. If that flow is worse for one cylinder, that cylinder can run hotter and be more prone to problems.
Exhaust flow is how easily the engine can push burned gases out. If it’s restricted, the engine can run hotter because the cylinder can’t breathe out as well.
Coolant pressure is how hard the cooling system is pushing the coolant around. If it gets too high, it can push coolant out through plugs or seals and cause overheating.
Turbulence is chaotic, swirling airflow that increases mixing and disrupts smooth flow patterns. The host argues that pulling air can create mostly laminar flow, while pushing can create more turbulence that may change how heat transfers.
A diverter is like a small piece of ducting that guides airflow where you want it. The idea is to make sure the radiator’s last section gets cooler air instead of bypass airflow.
EGT means exhaust gas temperature—how hot the engine’s exhaust gets. “EGT controls” are ways to keep that heat under control during towing or hard driving. In this segment, the host says you may need to reduce boost to keep EGTs safer, which also helps the cooling system.
A wastegate is how a turbo controls its boost. It decides how much exhaust gas goes through the turbo versus bypasses it. Changing it can change how hot the engine gets and how hard the cooling system has to work.
The Dodge Charger is a car designed to be fast and powerful. When people talk about it “moving air,” they usually mean the car uses openings and cooling parts to help keep the engine and other components from overheating. That’s important when you drive hard.
This is a part that helps manage the temperature of your transmission fluid. It uses the engine’s cooling system to either cool the transmission down or warm it up so shifting works correctly.
Transmission fluid is the fluid that keeps the transmission working and helps it shift. This episode explains that its temperature is managed by sending it through a heat exchanger connected to the engine’s cooling system.
Term
heat exchanger built into the radiator
A heat exchanger built into the radiator uses engine coolant temperature to influence transmission fluid temperature. The speaker notes it can cool the transmission during driving and also warm it in cold weather to prevent poor shifting behavior.
Lockup and overdrive are ways an automatic transmission can reduce engine revs and improve efficiency. The speaker says the truck may delay using them until the transmission fluid warms up.
An air-to-water cooler is a radiator-style setup where air helps pull heat out, and water carries that heat away. It’s used to keep transmission fluid from getting too hot.
The Lucid Air is an electric car. It uses cooling systems to keep important parts from getting too hot, and that can involve heat exchangers that move heat from one fluid to another. This helps the car keep working well during normal driving and harder use.
A torque converter is the automatic-transmission part that uses fluid to transfer power from the engine to the gearbox. When you’re working the truck hard, it can get very hot.
The Ford Edge is a mid-size SUV meant for daily use. Some design features can help the car in one way but create a downside in another way, which is what the “two edge sword” idea usually means. It’s often about how the car handles airflow, cooling, or efficiency.
A transmission cooler is like a radiator for your transmission fluid. It helps keep the fluid from getting too hot, which is especially important when towing.
LIVE
Hello, everyone. Welcome back to the Power Driven podcast. Today, it's just
Meyer and I. Todd is gone. He's actually on vacation. We thought a perfect
topic for this week would be vacation towing. If you're out there hauling
things with your truck on a family vacation, I want to talk about like
normal temperatures that you should see with your radiator with your
transmission. We get questions all the time, especially in the summer. Yeah,
I mean, it's towing season, camper season. It's 140 degrees outside right
now. So if you're going to have issues with anything overheating is the
season. And so first off, I think we'd start right with coolant temps. We
got a lot of questions about what is normal coolant temp going down the
road, pulling your truck, and what is a problem that you can adjust and how
can you fix that problem? So I mean, it depends a little bit on your truck and
the thermostat in it and how accurate your your sensor or your gauge is. Like
some of your early trucks, they're pretty approximate. Sometimes it's nice to
you get some weird readings, hit it with like a radar gun just to make sure
you're even in the realm like one of those infrared temp guns you can get
from Harbor Freight or just to make sure because they're kind of notoriously
not always perfectly accurate. So you got some weird stuff. It's always good to
just double check that. But let's just say it is reading correctly. Generally
going down the road flat ground, even like with if you had decent cooling
system, you should be sitting right there where your thermostat is opening. And
so that depends on what thermostat you have. Factory they range from call it 180
degrees to about 200 degrees opening temperature. People ask like, Hey, what
is there? Is there any downside to running 180 or any downside to running a 200
degree thermostat? Because you can get those ranges for basically all your
trucks. And I mean, I don't think there's any real bad downside. Like if you're in
the winter, the heater goes a lot hotter. Yeah, so if you get a higher temp
thermostat, it helps in the winter. In the summer, a cooler thermostat opening
opens earlier and it gives you a little bit of a you could say a temperature
headway like pre games the hill. So you start the hell at 10
degrees lower 20 degrees lower, you're going to hit that, you know, whenever you
let out point, which I generally do like 240, like 240 is where I'm like, Okay, I
should really be smart. Like this thing doesn't need to get me home. But you hit
that it takes longer to get there. It's not gonna like if you're sitting there
sustaining 235 degrees, you're not going to sustain lower with lower thermostat.
They're both going to be full out open at that point. But it's just going to take
you longer to get there. But if you're on a flat ground section or downhill with
a lower temperature thermostat, it will almost pre cool the radiator and all the
water in there a little bit, because it lets it do maximum cooling when you don't
need it. This gives you a little bit of a capacity, a little reserve capacity we
could call it. So that's one little little step or tip. If your truck is
hovering there 215 220 degrees. In my experience, that's not normal, especially
in older trucks. That's way above the thermostat temp threshold. Now is that
going to hurt the truck at 215? No, the boiling temperature water is about
211 degrees. Your radiator has pressure has a cap on it. Pressurized coolant
takes more temperature before it boils over. So that's why they put pressure in
the radiator because they designed them to be able to run higher than boiling
temperature. Fun fact for you guys, like at sea level, everyone knows boiling point
of water is 212 degrees in American or 100 degrees in off land centigrade.
Up here, we live at 5800 feet. I want to say that the boiling point up here is
like 208 209 higher elevation, lower pressure. It's going to off gas sooner.
Like, like, like the other day, I was making macaroni and cheese with my kids
and I was trying to teach my, my son, Jack, he's like a science nerd. You know,
I love him, but he just loves science facts. And I said, Hey, check this out.
And I put this candy thermometer in the mac and cheese water and it's only
like 208. And I was like, ask, ask Alexa what the boiling temperature water is.
He's like, Oh, our gauge must be wrong. And I was like, no, it's a high spot on.
So, so here, even at 6,000 feet, that boiling temp drops by about three.
But the air pressure is about three PSI lower here. So higher pressure cap,
15 PSI boiling temps up there over 230 between the antifreeze and the pressure.
Yeah. I mean, I've, I know a lot of people, I think the light turns on at like
245. So even Cummins from the factory was like, yeah, you're good for.
But, but back to back to temperatures and overheating, though,
um, if you're up there to 30 to 40, like that's not normal to be there.
It is normal at max load capacity on a truck. So if you have a brand new
fifth gen Dodge that's designed to tow 35,000 pounds gross or aren't someone
clerked like 40,000 now.
They're freaking nuts. I don't know if you're 40,000 and you're coming in
Death Valley, it should basically it should max out the cooling system at
your maximum towing level. If you have an old second gen Dodge, let's say you
have a 99 Dodge and you're pulling the camper and it has 200,000 miles on it.
That cooling system is not nearly as good as the factory cooling system
because it's got a bunch of miles and corrosion buildup and stuff.
You go in Death Valley. I don't think you're going to be, and you're going to
be towing more. A lot of people won't realize the gross max weight on those
things was like 15,000 pounds.
Yeah. That's pathetic. I've never seen that for the first time, especially on
a single rear wheel truck. You're like, dude, I can't even tow my trailer empty
with this. That's that's combined. That's truck trailer. Everything, you know,
you're, you know, you're, and so it's very easy to overload older trucks
because they just didn't have the radiator and the cooling capacity. It's easy
to have the power and get there. But so, but anyways, so if you're hovering
above that, there's two things I check whenever I see my coolant little high
one, I'm like, am I going up a grade? Sometimes it's hard to notice if it's
a slight grade. Yeah. Sometimes you feel like you're going downhill. You look
at the gauge. You're making 20 pounds of boost. You're like, Oh, this is actually
up. And so your boost is higher than normal. You know, you're pulling a
greater, you're loading heavy. The second thing I noticed is wind. And if you
can't see, look for brush on the side of the road, a flag, a ribbon, the little
road markers, wagging signs. If you're pulling into a headwind, I remember one
time Todd and I, I was pulling his Godfather. Oh, man, it's Frankenstein
truck. I can't remember. It was either Godfather Frankenstein. We went over to
a dyno event. I think it was Frankenstein. We wanted a dyno event in Denver, pulled
over the mountains with my second gen dodge on the way back into Cedar City. I
could barely my EGTs were really high. And I could barely maintain that. And my
coolant was like just about maxed out. I'm like, what the heck? Well, I get
looking, we're going in about almost a 40 mile an hour headwind. Oh, I just
didn't realize it. And his truck on my open deck trailer with that wind old
parasail on flat ground, you know, we're actually slight downgrade coming out of
Beaver Utah. I was like, I was expecting, you know, lower EGT. And that's when I
realized, Oh my gosh, that little bit of headwind made it as if I was pulling
about a 6% grade on, you know, relatively flat ground. So first off, make
sure you're not pulling the grade, you're not in a headwind and or your
trailer brakes aren't dragging or yeah, you didn't hook something with your
trailer and you're pulling three cars behind you. I mean, just the basics, you
know, as you would. But yeah, I mean, as far as like what's normal, though, like
if you are flat ground and you're just kind of cruising steady state, not huge
headwinds, like you should be able to maintain whatever your, your coolant
temperature, like your thermostat opening point is that you should be able to
maintain that. So for my truck, that's like 189, 192, like right there in that
range. If I'm flat grounding, it's sitting right there. And it does not go up
from there until you start pulling a grade or, you know, making, making some
power. But that's going to change. Like, I mean, even with Willard, same thing, I
don't know what the degree is, but there's a kind of a point on this, on the
gauge, it just kind of stays there and that just tells you everything's good.
It doesn't really move from there unless you're actually pulling a grade or
accelerating or whatever it is.
Now, there are differences in summer, like you get into Phoenix and if it's 110
out, and your AC is going, even if, and it's kind of not moving to kind of
stop and go, sometimes you can get some coolant buildup because you don't have
that wind over the front. And you get to realize a lot of these trucks, they have
a fan clutch and the older second gens, they're, they're mechanical. So when it
gets warm, that fan clutch engages on the newer trucks, they're electronic fan
clutch, they're, they're both. So it will kick on still, but yeah, electronically,
it kicks on and that's, I mean, for me on my tow truck, my fourth gen, it kicks on
at 210. If I sit the moment I hit 210, you can just hear the fan clutch kick on
and then you have to get down to 205 or something for it to kick back off.
But yeah. And so, you know, that fan clutch, so sometimes you get weird traffic
conditions or lots of stop and go, anyway, so, so these are problems you can
have with the coolant, but so let's say you've identified you have high coolant
at this point, it's, it's running abnormally high.
And that's another thing to look for too, is like how apt your cooling system is.
I mean, like sometimes you're just towing heavy and that's why it's running hot,
but like cresting the hill into Cedar, like that's, like we, you're pulling
grade for, I mean, you're going from was it, was it St. George 3000 feet?
A little bit less, like 24, 3,500. 24, 2500. And you get in a Cedar and that's
like a 45 minute trip and you're up here like a mile high, 58 something.
So you're just doing a lot of pulling. And so yeah, you're going to be sitting
there for me, it's I'm sitting there to 20, to 30, whatever it is coming up the
grade. And, but the moment I nose over into Cedar, there's a couple of miles of
downhill and I had some cooling issues in my truck. I didn't really realize it.
But what made me realize is I put nose over the grade and first of all, I was
having to like slow down because my coolant temps were sitting there.
I'm like, this is like, it's a lot of weight, you know, over 30,000 pounds,
but it didn't feel like it should be getting hot at that point.
But I was like, this is a lot of weight. It's kind of new to me towing that heavy
with that truck. I was like, this might just be the capacity.
And then I nosed over into Cedar and it would like took forever to cool down.
Like finally, when I got off the off ramp, I think it was still sitting at like 220.
I'm like, like that's miles and it cooled down to 20 degrees. Like something was
wrong there. So that was the, that was like the eye opening thing for me is like,
okay, I've got some kind of an issue. That's when I started digging into it.
Cause I mean, sure it's going to get hot when you're pulling a grade, you're making
power, but the moment you're done, it should cool right back off.
Another thing is like when the fan kicks on, it should cool right back off too.
Like even when you're pulling a grade still, like you hear the fan kick on,
it should cool down like five degrees and then maybe it keeps climbing from there.
But, and that's the first thing I tell people, especially if you have a 12 valve
or 24 valve early comments, if you don't hear that fan howling,
when you're pulling the heel and your temps getting hot, your fan clutch is bad.
Oh yeah. How can you tell if the fans on, if you do, do not have the radio on
and you don't know if your fan is on, it is not on.
Like it's, it's howling. Like there's no, there's no chance of you not hearing it.
If you don't hear howling, the fan clutch is probably half engaged. It's worn out.
It's not doing its job. And if it, there's a lot of cooling power with that fan.
I mean, it pulls almost 30 horsepower off the engine when it's fully engaged
at like 3000 RPM. And so it's basically a 30 horsepower cooling fan.
So while these guys are like, Oh, I got to upgrade to electric. I'm like,
as much as I hate to admit it, electric fans are not an upgrade on these trucks.
They have a mechanical fan for a reason. Semi trucks don't have electric fans.
They have big mechanical fans because they're, they're upward.
I mean, they might be pulling 40 or 50 horsepower, you know, of cooling capacity.
Anyway, the, the fan, you should hear it. If you're not hearing it,
that's your first step to get in there. If it's an electronic truck,
something 2003 or newer, if it's not kicking on, it's also possible that the fan clutch is bad
because the computer is not dumb. It's not going to see high temp and not, you know,
command that on as long as the circuit is healthy, which most trucks,
it's not a common failure. I guess one time we had the hard clutch cut
snagged by the harmonic balancer and ripped the wires out on Todd's truck one time. Yep.
So, and I've left it disconnected one time too, like just forgetting I was working in there and
left the fan disconnected and didn't throw a check engine light or anything. I didn't realize it until
I don't remember what I did, but I like popped the hood and I was like, Oh,
I've been toying with that unplugged for the last however long. And that's how I know.
Mechanically, it will still kick on just later. So when it gets hot enough, it still has a mechanical
override mechanical override for temp of something. So that would make it so you can't pregame the
AC wouldn't work as well. So then when you're solicit first step is the fan clutch. If the
fan clutch is working and it's still hot, your next thing is going to be thermostat probably
checking to make sure your thermostat is working. I mean, that's a super easy thing. You can just
know it's the old glass jar or glass measuring cup in the microwave and then toss the door in the
pot of water or whatever and just toss the thermostat in you want to see that thing travel all the way.
So that's like what they call like a wax motor. So basically, it's got a liquid wax,
well, a solid wax and then when it gets hot, it expands. And that's how it moves that little
plunger open. And so the thermostat is normally closed when it's at room temperature. And so
you put it in a pan of boiling water and you should be able to see that thing open up. I remember,
I mean, your boiling water is 212 degrees. So you should see it like open up basically all the way.
And if it's not, then you got a problem there. Also, another thing that a lot of people don't
know about the cooling system is it's not just an on off. The thermostat doesn't just turn it on and
off and like flow not flow. If you look at thermostat, I would say that most of them have that
there's a little puck on the very bottom. So it's like, there's got a little spring on it. Yep,
you got your main disc that gets clamped in and it's got the valve built into that. And at the
very bottom, there's like an inch away, I guess, there's a little puck. What that does is it makes
it so when your thermostat's closed, it opens up that valve and it allows the water that would
go to the radiator inlet of the water pump again. So it's basically short circuiting it
and and allowing the water to flow because otherwise you got all the stagnant water,
you got a lot of pressure in the system from the water pump, and you got a stagnant water. So
you're going to have hot spots with that bypass. It allows the cooling system to keep circulating
through that water flows through the block and the head comes back to the thermostat. And instead
of going out the upper radiator neck, because that little plunger is open, it goes back, there's
about a half inch tube that goes back to the suction side of the water pump. It's built right
into the block. Yep, it's cast into the head and the block, like that front corner of the block,
like above the oil filter that that front passenger or exhaust side of the block,
there's a little round port there that just sends that right back. And so fun fact for you,
electric pump water pump guys were like for like when we're doing our race trucks, we always get
rid of the thermostat because you just want it to be open, you want that thing to be able to cool
off in the staging lanes, you don't want to sit there and be sitting at the thermostat opening
point. But also we plug that bypass that way. Because electric water pump electric fans,
you're kind of a race truck, you want as much cooling as possible, you want to have control
of the cooling. And so if you take out thermostat and don't plug that, you're just circulating
half your water back to the inlet of the water pump. So and so a lot of people they're like,
oh, my truck's overheating and I pulled the thermostat and that didn't fix it. So
that's not the problem. If you pull the thermostat and run your truck down the road without it,
you have less cooling capacity. Because if it improves it, then the thermostat wasn't opening
at all. But if the thermostat was kind of half opening, you basically half of your water flows
recirculating back to the water pump, not going through the radiator and getting the max cooling.
And everybody's just like, Oh, it doesn't cool as well without a thermostat because it goes
through the radiator too fast. That's just fallacy these people have. No, it doesn't go through the
radiator too fast. Half the water is not going through the radiator because that bypass is open.
There's a little fallacy. A lot of people are like, Hey, if you run no thermostat, it goes through
the radiator too fast, doesn't cool. That is 100% false. And show me the law of thermodynamics that
tells us that proves that. But I understand why people come to that conclusion. Because if you
run without a thermostat, it does not cool as well. And that is why they have a built in
recirculation that is no longer getting plugged. And so your solution there, like if you were just
max effort tow truck or whatever, you're just you don't you want to bypass the thermostat.
Option one is throw a plug in that port. So it can't like, I think of 24 valve, you can tap
them to like, I want to say three quarter inch MPT or half inch MPT. Yeah, half inch MPT,
maybe three eighths is close. It's I think it's half. Yeah, half MPT, but you just throw a tap down
there, plug it. And it's quick and easy. You're not doing any permanent damage. You can throw a
thermostat back in if you want to, or you take your factory thermostat, or an old one or whatever,
and you start to drill some holes around the outside of the disk. That way that you have a valve
there, obviously, it's still going to open and close, but you got guaranteed flow. And that's
a good like test run to say like, Okay, I don't know if my thermostat is working. Maybe you're
questioning it. You want more testing than just throwing the thermostat in a bucket of water
of that's boiling water, you can do that and see what does it do? Does it super cool now? Or
does it still run hot? Still running hot? There's a couple things to look at. First,
before we get out of thermostats, one last little point I want to make. There is a difference between
the cheapest thermostat at the parts store, the gates, the whatever the Napa brand one and the
genuine Cummins ones, the genuine Cummins thermostats are better, they open more volume,
they're more reliable, they they're expensive, aren't they like $60 or something like that.
But I will say I used to be a believer, I mean, I'm kind of the king of cheap. And I've ran lots
of cheap thermostats. And crap, you can get a thermostat out of a big block Mopar and it fits
back. That's what I do in the winter on my truck, raise the temp because you can get a big block
Mopar thermostat that'll go, you know, 205 degrees and that really helps that heater temp. But
that thermostat does not open as big does not flow as well in the summer. So and these thermostat
manufacturers, all they care is that it fits the size. They're not necessarily making sure it has
the right flow dimensions and stuff. They're just basically saying it's compatible because it'll fit
and it's the wrong temperature, but or the right temperature spec, but it's worth it. In my opinion,
especially the second gen dodge, I don't know the third gen's, you feel the same as true,
a genuine Cummins thermostat is worth it. I've never tried anything else. I came from the 12
out of guys. So I just came kind of said the same thing of just just running Cummins one if you
can. That actually runs me of I told you about my my cooling system issues on my tow truck.
And I was trying to figure out something and I don't, this is what kind made me realize it
that it was a thermostat problem was in the wintertime or anytime you shut the truck, I don't
understand it, but you shut the truck off. Anytime you shut the truck off, you start up a gas station
doesn't matter. You started up the opening. It opened at a higher temperature for the first time.
So like it would get up to like 220 and then finally cool back down or like, and if you're
towing and you like got fired up a gas station and merely hit the on ramp and go, it would hit 240
or something before it finally opened and went back down. Remember that one time it like dinged
you and you thought it was your seatbelt. And I was like, I remember how you like you got dinged
like five minutes ago and you put your seatbelt on like it was actually my cool attempt, the cool
attempt light. And I didn't even notice I was driving. It was great. I loved that thermostat
for the winter because like you just get full heat and they're like baking there on your way to work.
It was great. But yeah, that was a, that was a great sign that my thermostat was not opening
correctly. That is not normal. And it's probably like, if you're having cooling system issues and
it has weird behaviors like that, there's a really good chance it's your thermostat. But yeah.
So we, so we hit on thermostat. So that's kind of the first thing. Some people will play with
fluid level. If your food level is low, obviously it's not going to cool as well. A lot of people
think if their antifreeze mixture is off, it's going to negatively affect. Yeah, you've got to
add more antifreeze so it has more cooling capacity here. And a lot of people understand this. A lot
of the, you can say heat transfer of a fluid has to do with the surface tension. So if it's a thick
fluid, it, it does not transfer heat in and out of the fluid as well as if it's thin or has lower
surface tension. Think about it like I'm trying to think of a way to describe that. But basically,
the surface of the radiator is not perfectly smooth on the inside. It's got some texture.
And so the lower surface tension, the more it can fit into the texture, the more contact it
can have with the aluminum of the radio. I'm sure it's also like, I mean, think about trying to
transfer heat with molasses, like the molasses that sticks to the side of the radiator or whatever
your surface is, like it's going to stay there and the rest is going to flow over top of it.
If you got like a thinner media, like water, that, that, that the layer that's stuck on the
side is going to be thinner and thinner. That would make sense. And so basically what I was
hitting on is fallacy number two, everybody's like, Oh, if it's overheating, you need to add more
ethylene glycol or whatever you need more of the actual coolant mixture in there. And in my
experience, straight water cools better than straight and then antifreeze of any ratio water
has lower surface tension. In fact, they make these water wetter red line makes
royal purple makes their purple cool. All these are is an additive that lowers the surface tension
of the fluid and makes them cool better. And that does work better. I used to put it in the
sand dunes, my dirt bikes, it would make a couple degree difference. It's not like night and day,
but there is a little bit of difference there, but just straight water cools better than antifreeze.
And so if you're right on the verge, and you're just trying to get over the mountain or limp at
home, straight water technically cools better than antifreeze. It also works better the heater
in the winter. If your heater isn't warm enough, straight water also, and that's how I learned
that firsthand, straight water may make heater work better. And I was like, What the heck? I was
like, Oh, I'm really going to get some heat now when I put the antifreeze so I can park it outside
and my heater went down. I'm like, that's where as you know, a young dumb kid, I was like, Oh,
antifreeze does not cool as well. And then as you start studying science and physics a little bit,
you're like, Oh, that's because the surface tension sense of ethnic glycol is higher. And so it does
not conform. But yeah, so water does cool better, make sure the fluids there. And there is a little
bit of advantage with a water wetter, cooling additive, you know, red line makes stuff, royal
purple makes stuff. A couple of them. So what else were we going to talk about? So I mean,
let's just say you've ruled out your thermostat, you still feel like you're running hot. I mean,
there's a couple things I would I would go to. So first off, your radiator, I mean, if it's all
like, especially if it's like a VP truck where they've got the breather right there, that back of
the radiators can be all gummed up all 12 valves have a level of it, where it just gets a bunch
of oil on there dirt sticks to it and plugs your radiator. So pulling it out, blowing it out,
whatever can really make a big difference. I mean, that's like back in the farm days,
like that was a daily maintenance item on our tractors, because you get like grassed seeds and
stuff that plug up the radiators on them. And you lose a lot of cooling capacity.
But I would say 90% of the trucks that I've ever seen that the guy says is cooling problems,
if they check the radiator, it is not free flowing. It's not going. So that's
a big problem that a lot of people miss. Now, some, some of you viewers, you know,
or listeners are going to be like, Oh, that's first thing I did was change the radiator or
whatever. And that wasn't the problem. So, but I would say 90% of the ones I've seen have cooling
problems. The outside of the radiator is dirty. The inside inside also is a problem. I had a
truck I put together my 12 valve back in the day, I fixed it up, whatever. And one of the issues
is it had cooling system problems. And I pulled the thermostat out of it. I didn't realize about
the bypass. And so I just pulled it out just to double check, you know, thermostat, and I could
get the truck up to operating temperature without a thermostat. And I was like, this thing is terrible.
And so I looked down the cap and on the second gens, you can just see down the whole row. And
there was like barely any water, like at idle truck running, you could barely see like a couple
trickles through some of the tubes, like they were so gummed up. And this comes to another one
is like people like, Oh, I'm going to put an aftermarket radiator and it's going to be a lot better.
Factory is a four core copper core, like it is a good quality, heavy unit. I would,
I mean, I think some companies like Mishimoto probably make a physically bigger one. They
probably cool better. I've never tested that. But your factory second generators are all like
these big gnarly copper cord things. Like I don't think an aftermarket radiator is that much
better, if any better, I especially until you go to a like a Mishimoto or like a good high quality
one like branded as being bigger. And I would argue most of the testing I've seen done, they're
comparing a cheap aftermarket to a premium aftermarket. But I too believe an OEM brass or
copper cord radiator is light years ahead of 99% of what's out there. And a lot of people
have a cooling problem, get rid of their factory radiator and like, Oh, well, it's a little dirty.
We'll just replace it. Not realizing that it's like those things are solid unit. Those are really
nice radiators. And yeah, you can't replace that for $300 or $150 on rock auto. Like,
there's $150 of copper in that radio. Oh yeah, they don't make it. I don't know if you get them,
but I would expect them to be six or $700, maybe $1,000 if the dealer still carried them. So,
but you got to realize that it's it's tough to get the cooling capacity. So simply just putting
a new radiator in it is not necessarily an upgrade. Yeah, you fixed your clogged up one.
What I did, I did a bunch of research. And what I did was I, I want to say I soaked it in,
I took it out and I soaked it in vinegar is how I got the calcium or whatever build up out of there.
And then I once I did that, I drained it, whatever. And then I put it in the truck
and I filled the truck with like a 50 50 mix of water vinegar and I took it for a trip and ran
it through it, whatever, and then drained it all out that night flushed it a bunch because you
don't want that vinegar just sitting in there. So I flushed the crap out of it. And that's the same
radiator that's in that truck today. And I mean, I towed with it. It was great. Like it has,
I can sustain about 350 400 horsepower with that radiator, just towing. So it's, it's like,
I would say as good as new. It's amazing. I flushed second gen dodges a lot,
trying to get the heater to work better. And usually it does the heater core is pretty thin
on them. And so when you get playing with acids and stuff, be careful, you can get in trouble.
I've used hydrochloric acid, like myriatic acid that used for cleaning concrete, obviously blended
down. So it wasn't like full strength, but that's like 30% hydro. I mean, there's all kinds of strong
acids you get there, but actual products they make for flushing radiators. I was a farm boy that
had right had vinegar on tap. So the flush product, like Preston makes one. And I think it's like a
citric acid base or nitrous nitric. I don't remember, but it's, it's balanced. So it won't
attack the radiator as much. It's kind of weak. So it's safe, but it's also slow vinegar works
a lot faster. Like I said, it had barely any flow. Like it was, I was like trying to save
this radiator. Like it was, it was like worst case scenario, but most of you guys, you're probably
not going to clean your radiator, especially if it already has an aftermarket one, spend 150 bucks
and just 200 bucks, wherever they are, and just get another aftermarket crappy one. I mean, I think
doing a flush isn't like, especially because you should be swapping your coolant every once in a
while. Like if you know, you got to swap your coolant, throw a flush in the day prior, you know,
just get all the crap out of there and then, you know, put your new coolant later. I, I think
that's a great option. Just keep everything clean. So what's your cooling system is, is all clean and
up to snuff and it has, you know, proper fluid in there. The next thing that, that we've seen,
we talked about fans and fan clutches, but the fans shroud is a big problem. That's true. I want to,
I want to, in the radiator talk, another thing I have seen, and this is not a big deal, but it's
little things help is the heater core. So factory, if you look at the fee, the heater core feed
fittings, any truck, 12 valve, common or whatever, they are feeding the heater core through, let's
just say a quarter inch hole. Like the feed fittings for all the heater cores that go into the head
or whatever are all about a quarter inch hole orifice, and it goes out to a five-eighth inch
tube and it goes to the heater core, whatnot. It's very common to redo your heater core plumbing.
You got like a compound set up aftermarket, trying to clean it up, whatever. You put generic fittings
in there to get to your five-eighth inch hole. And now you've got, I mean, ultimately your tubing
is your orifice. You've got like a half-inch orifice in there now. You got a half-inch orifice,
the way the heater core is plumbed as it goes from the pressure side on the head, basically
next to the thermostat, and it gets returned back to this suction of the lift of the water pump. So
we're talking about on the thermostat, how there's a bypass and everything goes through the bypass,
bypasses the radiator. Same story on the heater core. Everything that goes through the heater core
just goes right to the suction. Well, in the winter, you're cooling it down a little bit because
you've got the heater going. But in the summer, where that heater core is blocked off, it's not
losing any temperature. And so now you just got hot water going from the head right back to the
suction. And so making sure you've got either factory fittings or the factory orifice, or factory
ish orifice size in those fittings, make a big difference to, or at least a small difference.
It makes a difference trying to keep cooling temps in check because yeah, you're just bypassing.
And what's funny is, I mean, I've been doing this a long time. I did not know those fittings
were orifice down like that from the factory. So I just learned something here, guys. And yeah,
that's going to short circuit it. Now the guys, like the hot shot tow guys, they, they leave it
wide open and they turn the heater on and roll the windows down where they're pulling the grade
because that gives them an extra, you know, 5000 BT is a cooling capacity if you use the heater in
the summer. But you know, that's pretty, you know, the wife and kids aren't going to like that. You
got to be pretty hardcore to like turn the heater on and roll the windows. I'm not great.
It's still summer. It's not great. Another thing you can do, which is like more again,
your hardcore, but like you got your tow guys that, you know, you, you don't want to have to
slow down. You don't want to have cooling 10 problems, putting a ball valve or something
in line with your heater core, plug it off that way. You know, if you don't plan on using the
heater, close the ball valve. That way you got, you don't have any wasted fluid going through
the heater core. And then some guys claim that makes the AC a little cooler because there's
it's not keeping the heat out. You're not, I mean, it's not supposed to blow through the
heater, but there's a little proximity there. So it might make a little difference on your AC temp,
but definitely if there's no AC, it makes a difference though. I've noticed there's heat
comes out of there. If your AC is broken. So some of that heat creeps out of there. So yeah,
it does make a difference. So that's something I've seen. So then next, your, your cooling
system is up to snuff. You've got the stuff flushed and cleaned. The fan shroud is another
big thing. If you have a broken or I mean, mangled or seriously missing fan shroud,
that's what's directing that fan and making it more like a ducted fan. Ducted fans are a lot
more efficient than open. And so if you want maximum cooling, you need the fan shroud to be
in close proximity to the fan, just the factor ones, they work great. But if yours is gone and
missing, that's a that's part of your cooling problem there. So you need a good fan shroud.
Belt slips, not a big problem. You know, usually you'd hear that squealing. I don't really see
fan belt slipping blades. I've seen some people they bent their fan blades back in the day. They're
very expensive, good replacement fan for a second gen Dodge. They were just stupid money. And so
guys were retrofitting all kinds of random blades from stuff. So make sure the fan blades are actually
full size in there. But beyond that, you're kind of getting, you know, past the easy stuff. Now,
now you're looking at hardcore, hardcore diagnostics. Yeah. Blown head gaskets can heat
coolant very fast. But if you pull that cap, you'll see, you know, ugliness in there. It does
not necessarily be a milkshake, but you'll see like soot on the top of the water. So
blown head gasket is is a common. I see guys doing like those those fleece coolant bypasses,
those come out of the back of the block before the head, they go to the, you know, the top of
thermostat. So like that. So they so those technically aren't reducing your cooling capacity,
they're just pulling water out of the back of the block and routing it to the
different people do it differently. I want to say the fleece style, like they give you
the block, they move the thermostat up. So it's returning from the back of the block to where
the thermostat, no, no, I'm sorry, I'm wrong with that. They do return it, but they have a thermostat
built into the back of the of their block in the back. So yeah, you get that style. It should
work the same. You should people say it increases your cooling capacity because now you have two
routes for the water to make it out. I've never played with them. I don't know if I
I don't like having extra crap in my engine bay that I don't need. And so I've never played with
it. It's something I like to do one day just so I could like honestly bust the myth, but at least
prove to myself whether it matters or not. But I feel like theoretically you'd have less head
cooling with that. And so if there is less head cooling, potentially your thermostat could read
lower. Think if it doesn't, you know, if you're letting the head run a little bit hotter,
potentially you could feel comfortable in your gauge that it's cooling more. But really,
all you're doing is cooling the block and that temp sensors in that back corner of the head.
And so maybe on a 12 valve home rail, they're all up front by the thermostat.
So it'd make your com rails run hotter on the on the gauge because you're not putting as much
you don't put as much coolant past it potentially. But like I said, it's just more, I think they
became popular when guys would hot rod their truck higher pamp and it would pop the freeze plug out
of the back. And so they build a block off and they're like, Hey, let's route that coolant
somewhere. Which are the other the other thing I see people talk about is like, Oh, the number
six is always the first one to scuff, you know, so because it's running the hottest that the
it's at the back, there's no coolant back there, you know, the inland and the outlet are both on
the front of the engine. So by getting coolant past number six, it can cool down number six and
keep let it run cooler. I have a couple, I guess a couple thoughts on that. First of all, if you
head and the block, all the coolant passages are or fist, just got like, I mean, eighth inch
holes going through the gasket, except for the very back, that's where all your big holes like
your three quarter inch and stuff holes are. And so the gasket from the factory is trying to encourage
the water to go to the black back of the block, and then back to the front of the head and then
up into the head in the back and flow across the head now. So it is encouraging the back.
So I don't necessarily think that that's a huge, huge help. I know that number six is going to
run the hottest regardless, because the oil is, I mean, it's the furthest, the oil is what's cooling
the piston, and that's really the problem is the pistons getting hot, the oil is what's cooling
the piston. And yet it also has to travel as further. And so that that water, that oil is
going to be in the block for longer, it's going to be hotter. And so, and we know that number six
is going to run the hottest regardless, because if you look at like the head flow number six,
on both the factory manifolds are really most manifolds really, they struggle for exhaust flow,
they struggle for intake flow. And so yeah, number six is kind of like, I want to say destined for
failure, but it's destined to be one of the first issues because it is the least optimized,
followed by number one, actually. And so like when we machine blocks, we know that piston is
going to run hotter for many different reasons, we'll actually open up the clearance on number
six, just a little bit more than the rest, because it's going to run hotter, that's just kind of the
way of it. So yeah, but to answer the question, coolant bypass or not, I wouldn't say it necessarily
helps, but I also don't really think it hurts. And I think the idea behind that product years ago
was guys hot rod in their truck and blowing the freeze plug out from coolant pressure.
And that basically was giving them a relief, a system around the thermostat so that it wouldn't
do that. And so I think it accomplishes that if there's some side cooling effect,
I don't really know. I guess if you added a small inline radiator or trans cooler on that line,
you potentially could increase your cooling capacity, you could pre cool the water. But
I mean, we're talking like 90% of people aren't going to do that, you know, you might as well
add a second radiator in the bed if you're getting that crazy. But we had had did have some people
ask like, Oh, we heard you talked about a second radiator in the bed, like what are you guys running?
So first of all, we are not running anything. We run the factor radiator and it works,
it works fine. If you were a crazy hot shotter, what would you do to try to upgrade? I think the
first thing I would do is look at, I would do a bunch of research on the best possible radiator
out there. I think machine motors are good units. So I'd be tempted to run one of those,
see what that does. I would be tempted to they're heavy. There's a lot of aluminum there. There's
a lot more mass, a lot of heat sink opportunity there, a lot of places for air to touch. So
potentially of the aluminum ones, that seems to be one of the most robust ones. However,
I don't know if they're any better than a factory brass one. I know brass transfers heat or
I don't know if the new trucks have brass or factories. So I can't, I can't speak to that
factor ones like fourth gen is brass, then yeah, I don't know. But a lot of time, like we're not
talking a lot of there's not a lot of factory radars left. So maybe something to look at there.
I would be tempted to run a see if I can sneak an electric fan in there somewhere.
I had a friend that used to hot shot toe with a second gen dodge and they're known to not have
it's easier on a 12 or VP truck to add more power than you have cooling capacity. It's very easy.
The third gens have bigger cooling systems, but if you have a second gen dodge, it's very easy to
build more power than you have. So my buddy, he would put an electric fan in front of the radiator
in the AC as a pusher fan and the mechanical fan because that is the best fan on the engine side.
The mechanical fan has a lot of power there and he would have that on a switch thermostatic switch
or maybe even toggle switch as a pusher. He said he could tow another maybe 5,000 pounds and
he was doing a lot of stuff in Death Valley, you know, that really hot area there between Nevada
and California there. There's lots of really hot valleys and mountain grades there and
which I have an interesting thought on that. So when it comes to like electric fans,
like on a transmission cooler, we've done some testing in the past on put, put that push versus
pull. We measured, we actually come in scar right behind us. He has two identical coolers next to
each other. And so we, on the dyno, I wired up one to push and one to pull and we measured the
inlet and outlet temps of both of them. And then I flip flopped them and swapped them to like
rule out like one cooler was cleaner or whatever. And I swapped the fan blades around everything.
So it was, you know, pretty legitimate, legitimate test. And the pushing was about twice as effective
as pull. And I think there's two things that first of all, any kind of air pump,
like a fan is going to be more efficient in the push. But we're talking a little crappy electric
fan versus the big old mechanical fan. So you could say like, Oh, it's going to help a little bit.
I think there's also a strategy to the turbulence when you suck air through anything,
it's very lamp laminar flow. Like you, you do like any smoke tests or whatever. And you see
air getting sucked in, like whatever it is, it's like lofting in, it's about as laminar as it can
get. There's no laminar, you're meaning like straight, smooth flow for the laminar. Okay.
That laminar. When you have a fan pushing air, that air is extremely turbulent. Look at the exhaust
coming out of a hood stack. It's spiraling all that crap. Like it's very, very hectic. And well,
if that air is bouncing off of fan blades or the cooling fins and stuff, it's going to be able to
pick up more heat. And so maybe even that, just a little electric fan, it might have helped a little
bit with just the airflow, but it might have just been disturbing the air. So who knows, I'm, I do
want to play around with that a little bit going in there. Another thing that again, your big hot
shot guy or something you want to try to upgrade your cooling system or something to consider, I
want to play with the radiator. And so any heat that is being dissipated in your intercooler is now
going into your radiator. I also want to play with something of, if you look at the cold side of the
radiator, which is behind the intercooler hot side of the intercooler. I've always
wanted to play with putting a little diverter like sheet valve or not valve diverter, like
Finn or whatever in there to where the last six inches of the radiator gets cool air that by it
forces the air that's coming out of the intercooler to go shove, get shoved over. And that way that
radiator is forced to pick up cool air for that last six inches. And that way, because let's just
say the radiator is doing its job, it's cooling the air down to 120 degrees or something. If you got
160 degree air coming out of the intercooler, you're heating that air back up in the radiator.
And so you're kind of like stuffing it. So if you can divert that hot air from the intercooler
over, get cool air into the back of the last little bit of the radiator, that could help a
little bit. Also, when it comes to the intercooler, it's dissipating the heat created by boost. And
so if you got this like, I should say you got factory HX 35 and you've plugged the gate on it
and you can make 35 pounds of boost and you're pulling on the grades at 35 pounds of boost.
And go my EGT controls awesome, but now I'm running into the limit of the radiator. It's
really cool to feel like, Oh, yeah, dude, my turbo setup is awesome engine's awesome. Now I'm
just this little dinky inter radiators. The problem you might consider dropping the waste
gate back down and getting it to gate at 30 25, whatever it is. And this I mean, you got bigger
chargers compounds, whatever, same thing applies. If you're running into an issue with the radiator
and the cooling temps, but your EGTs are better, you might try dropping your boost down, it's going
to increase your EGTs a little bit. But it's also going to decrease the amount of heat in the
intercooler, which is then going to decrease the amount of heat in the radiator. So you might
sacrifice a little bit EGT control for a little bit better cooling system control.
So something to consider playing with your gates there, especially in compounds,
because if you just close gates, and you got a big charger, its job is to help you out and move
some air. And so just getting that gate to creep open a little bit can help the big turbo do its
job better. And so you may not even lose much EGT control. But as far as like single stuff,
yeah, sometimes you need to, you know, close the gate to have the best EGT control,
but it may not have the best towing performance.
So I want to talk about some kind of weird, weird things in the cooling system that people don't
know that, you know, just pop up like one thing I could think of the first time I was towing really
heavy in second gen dodge, I'm coming over hill. And once you get a second gen dodge up to 230 degrees,
the computer maxes out the gauge, like you're coming along to 25 to 26 just slowly creeping
as soon as it hits 230, it goes ding and maxes out and goes all the way over and like beeps and
and like I remember I was driving with Todd one time and I was like, oh my gosh,
and he's like first time, huh? And I'm like, what? And he's just like, you didn't know they do that?
I'm like, no, I've never, you know, gotten that hard overheated much. I've actually never done that
on a second gen either. And so once you get it to seriously, because the top white peg is 230,
once you touch that, it triggers and goes clear and dings and dinges and maxes out. Now that was
on a 98 dodge of mine and Todd also had a 98. So I don't know if the 97 does that, but definitely
98 through 2002 VPs. Once you get 230, so you'll freak out and be like, Oh my gosh, I'm boiling
this over because it pegged out the gauge. And then you sit for a minute and as soon as it comes
down, it'll come from pegged to like 229 and a half. And you're like, what the heck? And then
you get just a little hotter and ding and it maxes. And so that's like in the factory programming.
There's just a weird thing that people don't know, but I can give you a heart attack learning new
things. So just some weird stuff like that. Let's talk a little bit about the trans heat
exchanger. A lot of people don't understand how that works and how that can affect your cool
temps. Second Jen's first place to start, right? Yeah. So it's, I mean, it's pretty straightforward
concept. Yeah. I mean, a lot of gassers have the same thing. They, so the most typical thing
is that your transmission or transmission fluid, your hot transmission fluid from your cooler
will go through the radiator. There's like a heat exchanger built into the radiator. So you'll see
like your transmission lines going into the radiator, back out of the radar. It's using
cooling temp to both cool your transmission, but also in the winter, it's using it to help warm
your transmission to get up to temp. So that way it doesn't have any weird shifting or whatever,
because a lot of they don't even, they don't allow lockup or overdrive until it hits a certain
temperature. And so like if you're cruising with your truck cold all the time, like taking it to
work when it's zero degrees out, like you might take, go the whole trip without lockup or overdrive,
because computer's not, doesn't want it to come on because it's not warm enough. So that's kind
of like their solution to that warm up the trans on the dodges. They didn't want to put, you know,
on the second gen, they didn't want to put it in the radiator. So they added a heat exchanger,
which is funny because they put it in the V10s. The V10s have the heat exchanger in the radiator.
I'm pretty sure. Yeah, it might have been, I couldn't be wrong. I think they did. I really
think they did because they also, they changed them because they don't have this, the notches on
the inside for the intercooler to go through. But anyway, regardless, Cummins second gen,
they decided to put a heat exchanger, a little like, I don't know what you call a little cylinder
looking thing kind of underneath the exhaust manifold, six inches diameter, like a button half
long, looks like a propane bottle, like fat ones for camp stove, but like maybe about two of them
in length. And its job is to, again, either cool down the transmission when it's really hot and
or help cool down the transmission when it's really hot or warm up the transmission when it's
really cold. After the transmission fluid goes through that thing, it goes through a actual
air to water or air to oil cooler in the front of the truck, like in front of the intercooler.
And then that cools it down the rest of the way. And it heads it back to the transmission.
And so if you're pulling a grade and your torque converter is unlocked, that's where it's making
the maximum temperature in the torque converter trans is working there. It's running hot fluid
into that heat exchanger. And your truck engine in your second gen, it's pulling coolant right
out of the right above where the water pump is, there's a little water pump outlet. Yep. So it's
like a water pump outlet. So it's taking the the coldest possible pressurized water, water out
of there. It's running through the heat exchanger and then it's returning it to the suction side
of the water pump returns it right there. It's teed right there. So basically it's preheating
the water going in there. So yes, your transmission cooler does affect and heat up your if nothing
else. Yeah, it's bypassing. So not only is it bypassing like the heater core or anything else
bypassing the radiator, it's also heating it up on the way. So yeah, it does. So it's a two
edge sword though. So most plot trucks that that hurts you that makes your truck overheat faster.
What I tell some customers is like if you can get your transmission and keep it and lock up
and add an external transmission cooler, deep pan unless you can get your trans so it's only running
140 150 degrees down the road, even on the mountains, it technically can cool the it can
help the radiator because if you're at boiling temp and thermostats wide open, the water coming
into the water pump out of the radars at 230 degrees, if you can cycle 150 degree transmission
oil through there, technically that heat exchanger could be an extra cooling source.
But I mean, you'd have to be there. You have to have a really good system for that to work.
So a lot of guys are just like, I'm just going to delete that or whatever. And
I've had trouble with transmissions overheating with just the cooler on the front. When you're
towing a street truck around empty, usually you're okay, depends on your converter lockup strategy
and that but I generally tell people that that kind of get rid of or not. I've seen a mixed
water and oil. And that's a I mean, you obviously your cooling system is going to work like crap
with a bunch of transmission fluid in it. However, a lot of times really you just put a bunch of
coolant in your transmission fluid, and you can hurt transmission pretty quick with a bunch of
water in there. And so I generally just try to get rid of it if I can, just because I'm not a huge
like, it's just like a such a sucky way to end a road trip, because now your transmission doesn't
shift because you just put a bunch of coolant in there. And so I generally tell people that's
best to get rid of it unless you need like you live in a super cold climate or whatever. And then
yeah, you know, you're getting some at least you some benefits from it. But otherwise, I would get
rid of it. See if your factory cooler is enough like say factory does a lot of unlocked
towing and like they they they expect it to make a lot of heat, you get an aftermarket converter
in there and that is more efficient and you be more like smarter while towing with it and keeping
it locked up more and you can use just the factory OEM air to oil cooler and it could probably be
fine. Otherwise, throw another cooler like under the bed or double up factory coolers or whatever
you got to do, just add another cooler. It's generally the right option because people wonder
like, Oh, you know, what happened? Like, can you make your transmission run too cold? It's kind
of hard to do. Like I like my dad's truck, it'll get up to like 140 while he's towing. And it's
great. It just has two factory coolers in there. And it works awesome. He's like, is that too cold?
And I'm like, no, like as long as you can keep the moisture like get hot enough to steam off the
moisture every once in a while, like, it's fine. People like if you talk to like other,
like more factory OEM applications, different transmissions, whatnot, they're like, Oh,
no, you need to get away hotter than that. Yeah, oil does like it'll keep the moisture
out of better if it's hotter. However, we're talking about performance builds, performance
transmissions, that factory OEM pump was really designed to make a certain amount of fluid flow
pressure. We are taking that word. We're one and a half times in it, we're two times in it.
When you make that much more pressure, all the leaks everywhere are going to leak more,
that colder fluid is going to just help keep everything alive longer. And that colder,
thicker fluid is going to leak less out of all the little spots that the transmission leaks.
I mean, there's a bunch of designed to leak leakage points. And so by keeping the transmission
fluid colder, thicker, it's going to leak less. That means you got more fluid for the cooler,
more fluid for all your lube circuits. It's just happier. But most of you guys that have,
let's say 2003, a newer truck, most of those transmissions have thermostatic bypasses built
into the cooler that usually operate around 185. So I think the minimum temp that most OEMs
design the transmission to run at about 185 degrees. And we've seen no ill effects running
lower on these hot rod trucks. But at the same time, that is what they designed. Some of that
is fuel economy standards, thinner oil has less drag, less friction, it's going to be more efficient,
you know, when they're doing the fuel economy stuff. Most transmission builders will tell you
the lower you can keep the transmission temperature, the longer the seals and those moving parts will
be happy. Oh yeah. And so because heat bakes all those rubber viton seals and you can tell
transmissions that have run hot their whole life, those this like you take them apart, those piston
seals are just stiff. And that's probably the most common failure on stockish builds is a piston
seal will fail and then it'll burn up the clutch because it can apply it. So you know, you got to
you got to figure out what source you're trusting, you know, I mean, maybe if you have an l5p or
something and an Allison, who knows, I don't I don't have a ton of experience around what they
run. But I have noticed a trend on most newer transmissions, they want them hotter. But like
my wife has a GMC Yukon, the you know, 2021 model and I watch the transmission temperature
all the time on that and that's a 10 speed. I rarely see that over 190. Like and even when
we're towing or going up a hill, good thermos, it's it works really well. Her old transmission,
we'd climb a model, she also added a Yukon like a 2011 model. When I get to the top of the mountain
passes here, it'd be like 225 degrees 230 degrees and it bothered me one time transmission
temp turned on. So it was like summer and I was like, we're empty. We're not even pulling and it
hit temperature. The transmission was healthy. It just didn't have enough cooler. So I put
later when I lost the torque converter on that thing, I put a bigger cooler in there. And now
it would never get over about 180 climbing the mountains and in the winter. Sometimes it'd be
like 130 says all would get to your driving sub zero temps never had an issue with that
transmission worked great till the day it died. You know, which was a couple days
and your transmission didn't die. It's still great. Got sideswiped. So so
but but yeah, so so transmission temperature, that cooler does add that I have seen in weird
obscure cases where a ruptured transmission cooler leaking fluid, they put transmission fluid
into the radiator did not cool as well. So it's very obvious when you pull the cap and there's
this pinkish slime from the transmission fluid. And then your transmission dies right right there
because when you shut a vehicle off hot, the thermostat, the cooling side has pressure and
the transmission pressure goes away. That's when it back feeds a ruptured cooler and then puts
coolant in the transmission. And that dies very, very quickly with fluid where your truck's just
going to run hot. The transmission does not like coolant coolant destroys it very, very quickly.
It'll like the laminate clutches. It's bad hurts all the bearings that rust stuff. It's just
weird sludges. Yeah, you get water and oil and you like you you put water and oil
in them in a beaker like they separate you sit there and you mix it forever. It turns into
this terrible sludge and a P and a 48 re pump is a very good mixer. And so it just it clogs.
Yeah, it's just it's a bad bad news. So really quick, we kind of beat the coolant temps to death.
Depends on your model, you know, what's too hot? What's not what's normal? Let's go over that.
How much should be able to so I guess you've got a pretty stock ish 2008 like what to what coolant
temps do you see? So my truck towing, let's say the most I tow is maybe what 15,000 pound you've
got a 12,000 pound was a 12 k rated so it's like 12,000 pound enclosed trailer was what the length
28 foot the 28 foot bumper full enclosed trailer full height full height and highest I've ever
seen my coolants like 225 ever pulling the mountain. Yeah, you your your truck just mobs
like it's got factory turbo or sorry one of our factory size or one of our factory replacement
VGT chargers. So a small bump in an injector. It's basic tuning and that's like that's it.
But you also look that truck was rated to tow what 21 maybe 24,000 pounds and I'm towing 12.
So to me in the mountains in the Rockies in the desert in the anywhere I've towed,
I've never seen over 225 I've seen the transmission temps get higher than that. I've seen
the transmission temps get higher than the coolant several times. Yeah. And to where I
wanted to upgrade the cooler so I feel like my truck did not have as much transmission cooler as it
had rated as it had radiator but to me that's normal. So to me if somebody's telling me they're
hitting 230 and they got a light trailer I'm like something isn't right there. My second gen
Dodge so 98 12 valve if I was pulling that same trailer in the summer and these things it would
get up to 230 on the hills that absolutely it would get and it would it would max out the gauge
if I remember though I have enough power to pull at 80 miles an hour if I grab third gear and slow
down to 65 like a normal person or or even drop it down to 500 horsepower like my third gen
tows with then it probably still hit 230 doesn't have as much cool thing as 500 but for the record
I don't think you're towing with 500 horsepower in your third gen 485 is what the tow tune makes.
I don't think you've done on the tow tune. Oh we changed it huh. So I don't I would guess it's
about 400 like it's a good towing setup you're right there with everyone but still
like 400 yeah yeah and so now I've taken Willard and I've towed Todd's trailer with my racetrack
in there so it's a this is our 2000 2001 EP 44 truck got a bunch of YouTube videos on it but it's
got when I towed with it it had a 62 67 and our stage three injectors so it's a big injector
it didn't it didn't tow as well as our stage two injectors but that's why I just towed it with it
just see how well it would do went down to St. George and back and I was very pleasantly surprised
like I was able to basically set cruise control up the whole grade I did lose speed a couple times
I was in like tune I want to say tune three or whatever it was and if I
click it in tune four I'd maintain speed but EGTs were a little bit hot and so I bumped it back
down to three I lost like let's just say I had cruise control for 80 I got down to like 70 twice
like not terrible and coolant temp was great the whole way it was you know what was that in
May it was like May 1st or 3rd or something like that so it wasn't super hot it was dark out so
it wasn't like a super hard like you get in the middle of summer that really makes a big difference
but I was very pleasantly surprised with Willard like it's probably got a really good
coax system in it because I was able to maintain I know that's like a that's a high 300 horsepower
tune and it was able to maintain it no problem I think it's 382 is what kind of rings the bell so
very happy with that my tow truck I kind of beat the sound of that one but my
tow tune makes about six I want to call it 650 is like the I can tow anywhere with anything
for indefinitely and it's just compound turbos it's not just a single turbo with single turbo so
it's a it's a one of our VGTs on the manifold with one of our 480s on the atmosphere and I've
I've floored it for if you've ever been in Perump come in the grade out of Perump into Vegas
it's kind of a weird one because it keeps getting steeper and
but the speed limit keeps going lower and so I was losing speed but basically
at the same rate as the speed limit kept changing and so I was I had like basically had it floored
for the whole like it was at least 30 minutes coming out of Perump and the cooling temperature
was great it was like two 230 just sitting there and so two normal max load like that with 650
horsepower 230 is a good max for you I let out a 240 so 241 I start getting out of it but I was
like yeah sitting like 220 230 the whole time and then that's when the thermos sets are getting
worse and worse like shortly thereafter and then I put a new thermostat in it now like I've towed
to Vegas with two trucks on a 40 foot gooseneck and I think the fan turned on twice so something
about the tuning like that's a big one like say the tuning keeping the heat out of the intercooler
dropping boost down so you're not poisoning the radiator that was seen to it works really really
good not just making stupid boosts all the time that's an issue I seen someone was saying like oh
compounds don't work great on tow trucks because they make a lot of boosts I'm like you got to size
everything correctly like someone has a very identical setup to me but I think the main difference
is just tuning and so they're making you know for 60 70 pounds of boost pulling grades and
my tow tune does 38 pounds that's it and that you have to yeah and so it was a huge heat difference
in the intercooler and there's a yeah my fan kicked like it kicks on a 210 and my fan kicked on
twice on the trip to Arizona and back and so like I could basically do I can flat ground 190 is where
it opens and you start pulling a grade you start getting up to like you know 205 maybe use a long
grade it'll hit that 210 and then it kind of caps out at like like like grossing 32 000 pounds
it depends on how long you're pulling the grade and how hot it is outside but 220 is pretty common
to hit I guess and then like I haven't had to let out of it for cool and temp since I put the new
thermostat in so so then an example of something that's not right I used to have a 99 dodge five
speed I had swapped a a HE 351 stock turbo on there and I lived in Vegas and I drive around in the
AC and the heat all the time running empty and I remember I was driving up to Mount Charleston
I had to a job I had to go manage because I was doing construction management and while I was
driving up that mountain to Mount Charleston when I was trying to pull the hill in fifth gear
and letting it lug it let's say like 1700 rpm or something EGT would sit there at 1200
and back then we didn't have a lot of tuning options and injectors were yeah what they were I
mean that's jammer five nozzles I mean who know I mean eight whole there's all kinds of weird stuff
back then but I remember my coolant would start getting up and it was like getting up it wouldn't
max out but it was climbing and I'm like this is a tow truck and it's empty and it's running up the
hill and I came to the conclusion that high EGT was the problem if I dropped it down to fourth gear
we're at a little more rpm it EGT EGT would come down about a thousand degrees and my coolant would
come back to like you know normal range right with thermostat opens or just a little above it
now later in life as I towed with the truck one more I realized what was wrong with that
truck it actually had a bad fan clutch and so the fan clutch wasn't kicking on and when I would
lug it in fifth at low speed it didn't have as much water flow through the radiator and stuff
and when the EGT was at 1200 it would have enough temperature that it was like
overheating so running empty with your tow truck of a mountain with it getting hot that is not normal
that is and it was simply a fan clutch is with that truck ended up being but for a while I fleshed
the radiator and played with all kinds of stuff didn't even I mean I knew what a fan clutch was
but I was like well I mean it kind of has friction it's probably okay and yeah it wasn't so speaking
of dumb pulling grades and second gen problems one time I had just done a head gasket on my second
gen and I was driving it out to Missouri visit the homeland and the thermostat stuck open as I was
going going up to Vale so it's snowing out it's icy roads all that stuff and I have no heat in this
truck and I'm kind of miserable and I was like man this is kind of sucks I'm like how
can I get this thermostat to close again and so I was like well maybe if I get it up to temperature
to where it could actually um like if we could it could open itself maybe that'll unjam it and I
could get it to close again so I was like okay well it's stuck open like you pull up grail it's
snowing outside it's cold so I put in going up Gravelle like the bad part like when it's super
steep I put in foil drive and I sat on the brake and foil drive like boost boost breaking it like
going up the grade like 40 miles an hour or whatever just got the thing hot and it fixed it
I was able to get my heat back but I probably look like a dumb kid the whole time like smoking
out everyone the brakes are red hot and the power breaking up and it's like I mean it's
snowing this water like water and ice on the road the brakes are red hot steam and the hell people
are like I mean if anyone saw me they'd be like what the crap is this guy doing but it worked so
you know weird situation stuck on you can beat the crap out of your truck for no reason it might
fix it that was a fun one I forgot about that well guys I I didn't have anything else are you
good mar I think that's it I had a couple people ask me like questions of the truck
what's normal what can they do what they should look at and we decided to kind of do this podcast so
I think we're good that's everything I wanted to cover thank you guys for tuning in be sure to
like and subscribe and comment if there's other topics you want us to cover or something you
saw we missed hit it up in the comments people read the comments we and
you can help everybody out it's kind of like a community there and we'll catch you next time
on the power driven podcast thanks how long was that when you do
About this episode
Coolant temps that “feel fine” can still mean your diesel is overheating—especially while towing, climbing, or fighting headwinds. Hosts walk through what normal coolant behavior looks like around the thermostat opening range, why pressurized systems and altitude change boiling risk, and how older trucks can have approximate gauges. They also cover practical diagnostics: check fan clutch behavior and noise, then thermostat function, and don’t forget radiator airflow, bypass paths, and clogged radiators. Transmission heat and coolant contamination are flagged as fast failure risks.
It's towing season and if your gauges are climbing on the way up the grade, you need to know what's actually normal and what's a real problem. Will and Myer break down coolant temps, transmission temps, and everything that can push a Dodge Cummins diesel truck out of range while towing.
They start with what a healthy cooling system looks like going down the road. Thermostat opening temps on these trucks typically run 180 to 200 degrees depending on year and setup, and they explain why a hotter or cooler thermostat matters for winter heat versus summer towing, along with how boiling points, radiator cap pressure, and elevation all affect what your coolant temperature can handle.
A big part of the episode covers fan clutches, since a bad cooling fan clutch is usually the first thing they check when a diesel truck runs hot. They explain how to tell if your mechanical fan clutch is engaging and why electric fans aren't actually an upgrade over the factory setup on these Cummins trucks.
From there they walk through testing a thermostat the old school way with a pot of boiling water, the bypass port a lot of guys don't know exists in the block, and why a genuine Cummins thermostat is worth it over the cheap parts store version, especially on a second gen Dodge.
Radiator condition gets its own conversation too. They cover why a clogged or dirty radiator causes most cooling problems, why a factory copper core radiator often beats a cheap aftermarket one, and how they've flushed old radiators back to life with everything from radiator flush products to straight vinegar. They also get into heater core plumbing and why oversized fittings from a repipe can hurt your cooling in the summer.
The conversation wraps up on transmission cooling, the second gen's heat exchanger setup, why factory transmissions are designed to run around 185 degrees, and why colder fluid on a built performance transmission tends to live longer.
Along the way Will and Myer share real diesel towing stories, from Willard's cooling performance on a run to Saint George to a second gen Dodge gauge that pegs out hard at 230 degrees, plus a few lessons learned the hard way about fan clutches and stuck thermostats.
If you found this useful, subscribe to the Power Driven Podcast on YouTube and follow along on your favorite podcast platform.
Will and Myer reference several parts from their own builds throughout the episode, including compound turbo setups, VGT turbochargers, and stage two and stage three injectors. Shop everything mentioned in this episode at PowerDriven.com links below.
