I Speak Jeep Mar 25, 2026

The Truth About Plastic Under Your Jeep’s Hood

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Concept

four-wheel drive

Four-wheel drive powers all four wheels, which helps the car grip better when the road is slippery or uneven. It’s especially useful for off-roading.

Concept

4x4

“4x4” just means the vehicle can drive all four wheels. That helps it handle rough or slippery terrain better.

Brand

Jeep

Jeep is a car brand that makes vehicles built for off-roading. When people say “Jeep” in a podcast, they usually mean the brand’s 4x4 models and how their parts work.

Company

Mishimoto

Mishimoto makes aftermarket cooling upgrades, like radiators. The hosts are talking about how the results didn’t match what they expected.

Company

Griffin

Griffin is a company that makes aftermarket cooling parts, like radiators. People choose brands like this when they want better cooling than the original equipment.

Term

fasteners

Fasteners are the bolts that hold the valve cover in place. If there aren’t enough of them, or they’re placed poorly, the cover can sit unevenly and cause leaks or damage.

Term

interwebs

“Interwebs” just means the internet. The speaker is saying that in the 1980s you couldn’t easily search for and order parts online.

Part

Radiator

The radiator is part of the cooling system. It helps keep the engine from getting too hot by cooling the liquid that circulates through the engine.

Term

steam

If you see steam under the hood, it often means the cooling liquid is getting too hot and boiling. That usually points to a problem in the cooling system.

Part

Cladding

Cladding is the protective trim on the outside of the vehicle. It’s often plastic and helps shield parts from dirt, rocks, and everyday wear.

Term

oil cooler

An oil cooler is like a little radiator for your engine oil. It helps keep the oil from getting too hot, which is important for engine protection.

Part

valve covers

Valve covers are the covers on top of the engine that help keep oil from leaking out. They also protect the parts under them and use a gasket to seal properly.

Concept

cold air intakes

A cold air intake is a system that tries to bring in cooler air from outside the engine bay. Cooler air can help the engine run better, but it depends on the exact kit and how it’s set up.

Term

heat transfer

Heat transfer is how heat moves around. With intake parts, it matters because hotter intake air can reduce engine efficiency.

Part

throttle body

The throttle body is basically the engine’s “air gate.” It controls how much air gets into the engine, and the parts leading up to it affect how well the engine breathes.

Term

thermal conducting properties

This is about how easily a material lets heat pass through it. Metal usually moves heat more easily than plastic, so the engine bay can heat them differently.

Concept

Engines are air pumps

An engine’s job is to pull in air, mix it with fuel, and burn it to make power. Cooler, denser air usually helps the engine make better power.

Concept

R&D

R&D means research and development—basically the work engineers do to design and test new ideas. Here, it’s explaining that the change wasn’t random; it was engineered.

Term

push rods

Pushrods are parts inside the engine that help open and close the valves. Some people prefer older engines that use pushrods because they’re familiar and often simpler.

Term

crank windows

Crank windows are windows you open and close by turning a handle by hand. Power windows use a button and a motor instead.

Term

oil filter

The oil filter cleans the oil that circulates through your engine. If the filter isn’t right for your Jeep, it can affect how well the engine stays protected.

Concept

reverse engineering

Reverse engineering means copying something by taking it apart and figuring out how it works. With car parts, that can be risky because the copy might not be made as well as the original.

Term

chemical process happens

The speaker is saying the plastic isn’t just heated—it actually changes chemically. That’s what makes it act more “permanent” after it’s set.

Term

molecules of the plastic

Plastics are made of long chains of molecules. Heating can change how those chains are connected, which is why the plastic can become more heat-resistant—or start to break down if it gets too hot.

Term

head gasket

The head gasket is like a seal between the engine block and the top part of the engine. If it breaks, fluids can leak or mix, and the engine can start running hot.

Term

Polyethylene Tertone

This is the name of a type of heat-resistant plastic. The exact name in the transcript is a bit unclear, but the point is that different plastics handle engine heat differently.

Term

carbon fiber

Carbon fiber is a strong, lightweight material made from tiny carbon strands. Race cars use it because it helps the car feel more rigid without adding a lot of weight.

Concept

cleaning out an artery

They’re using a health analogy: if a passage is “clogged,” flow gets restricted. In an engine, carbon buildup can similarly block or restrict small channels.

Term

Derometer difference

This sounds like they’re talking about the seal material’s firmness. A slightly different firmness or shape can help the seal fit better and stay sealed longer.

Company

Felpro

Fel-Pro is a company that makes replacement gaskets and seals for cars. The host is saying you’ll often see their sealing materials on Jeep-related repairs.

Term

all-aluminum cooler

An all-aluminum oil cooler is made mostly from aluminum. Aluminum can move heat away from the oil efficiently, which helps the engine run at safer temperatures.

Brand

Mopar

Mopar is the official parts brand for Chrysler/Jeep (Stellantis). If something is a Mopar accessory, it’s usually made to fit your Jeep correctly.

Concept

re-box

“Re-box” means the part is made elsewhere, but it gets put into a different brand’s box. So the label changes, but the actual product might be the same.

Company

AutoZone

AutoZone is a store where you can buy car parts without going through a dealership. The point here is that you can often buy the same kind of part yourself.

Concept

This is the episode’s main argument: plastic components in the engine bay aren’t automatically inferior to metal. The speaker frames plastic as a normal, long-term design choice rather than a temporary compromise.

LIVE

SFJ 4x4 Studios presents

In my oversized four-wheel drive Jeep

A Jeep podcast starring industry experts

Cure monocity

What? Say that again!

With mad scientist Scott Brown

I use my drill press as a sort of lathe

Our host, Neil Simpson

If one light goes on they all go out

Phil Bruce Shenanigans

We are really professional with Jeeps

This is I Speak Jeep

SFJ 4x4 Studios presents

In my oversized four-wheel drive Jeep

A Jeep podcast starring industry experts

Cure monocity

What? Say that again!

With mad scientist Scott Brown

I use my drill press as a sort of lathe

Our host, Neil Simpson

If one light goes on they all go out

Phil Bruce Shenanigans

We are really professional with Jeeps

This is I Speak Jeeps

Good morning, afternoon, evening, wherever

However you are joining us

I got real excited in my head because I can't wait to share with you all listening at home

There's a couple things going on

But my name is Neil with Simpson Family Jeeps

SFJ4x4.com

Are you sure?

I am very sure

And I am joined in Grandma's couch studio

By Dose individuals

I'm just a figment of your imagination

I am just thrilled to announce that

This is episode 200

Because of that, Jeff came running in

Like his hair was on fire

He was here to be part of this historic 200th episode

Which for only having 200 episodes

Are listening

You, our listeners, our followers at home

Have made this podcast

I'm already starting the

You're gonna help me out with all the words

I can't say later

I can't wait

This is gonna be a great episode

I have made this podcast

One of the most successful Jeep and Off-Road podcasts

Globally in the world

That is so stinkin' nuts

To hear that that many of you want to hear about

Jeep-specific

That they want to hear

They want to hear about you and I just drone on

For hours and monitor

Well, that's probably because

The actual sleep

You know those sleep courses

They actually cost money

So we're ASMR

Right, that's what it is

I don't even want to go into that acronym

But I know that you have to pay for those sleep apps

And we're probably free

But, but, but, Jeffrey

The producer is back in studio today

I am

Glad to have you here

I left you hanging right on a kind of

I knew you were coming

Right to the very end

I knew you were coming

That's okay

You know

You were on my seat

I'm like, nope, get out

Well, that's because I was trying

Desperately to thumb through the

The system to make sure it was up

And loading for you

We hadn't quite pulled out the manual yet

But we were getting there

Yeah

And then the mad scientist

Yeah, the maddest mad scientist

And in our 200th episode today

We are going to, as we had mentioned to you before

We are going to be talking about

The dastardly

And evil and unfortunate

Plastics in your engine bay

Plastic

I also want to note that

For funsies purposes next week

Prior to Easter

We will be talking about

The Harry Potter sorting hat of Jeep ownership

I'll just leave it at that

That'll be fun

And then there will not be a live podcast

On Easter Monday

We're going to take that day off

For you all listening in that capacity

We may or may not have some type of other episode

For upload purposes

But just outlining what we're doing through the week

I did see we had a new first today

We did

Billy Joe got first saying good morning

Good job Billy Joe

Nate says good morning

Rob says happy spring

Jaga Jeeper says good morning

Lucky McDeerhead

A lovely spring day here

Snowing

Griddle and Jeeps

Morning fellas

Nate said what can I say except

You're welcome

Based on the 200

I was never able to read it

Congrats on the 200 episode from Billy Joe

Daddy Jeep said they're all coming for the chat

That's probably true

Nate said I thought the microplastics

Were in my food and beverage

They're in your engine too

And Nate says inconceivable

So as a friendly reminder

For our wide and broad listening audience

And while that is the majority of you

We welcome you on whatever Monday

That you can make yourself available

Log on on the book of faces

Or the YouTubes

And get involved in the chat box there

Hang out and share

And see if you can beat Nate

Nate's on fire with all the references

So just in response to that inconceivable

I do not think that word means what you think it means

He'll understand

Oh boy

A princess bride

I almost said princess

Oh I know exactly what the reference is

Scott has no idea what it is

Such a classic

It is a classic

And without totally derailing already

Just making references

Because I can absolutely just make

Multiple references to that movie

We do

Well Scott cannot

I think I saw it once but it doesn't

In my brain so it's fine

Scott would have a good time with the ROUS's

My name

No I'm going to not do it

You started it

I need my notes drawn on

What are we doing here?

Hello buddy

I knew you were excited

I didn't know we were cuddling this morning

I was excited

Do you see what his notes are on Jeff?

It's on his turnpike violation

It's on my turnpike

I ran the toll booth folks

Don't worry they mail you

And we're off the rails

Don't worry folks they mail you

Your violation

Or is that a bridge fee?

No it's the turnpike

It's absolutely full by plate

When you run the toll booth

No that's a

That's a thing

Anywho

A couple episodes ago

We had

Elaborated upon

Our general frustrations

With radiators

In specific

Situations

Yes specifically Griffin and Mishimoto

And I'll continue to shout that from the rooftops

And what we were sold

A decade ago

Was that

Let's go back to the

The inception of the JK

That we had radiator problems

And there was mounting locations

And there was flexion

And there was rigid mount

And there was whole bunch of stuff

We actually have to go back behind that

We're not going to the horse though

Broke that streak I'm sorry

So wait I'm going to ask

How did you keep the horses cool

Go ahead there you go

We had the horses swimming last week

Don't worry

We didn't have plastic for water pockets

For our horses so I can't

Go back that far

But we were

If you've been in the Jeep game long enough

Everyone's been touched

By a TJ upper radiator tank

Just exploding

At some point

Wait wait wait

Let's go back to plastic valve covers on CJ

I forgot about that

We can go back further

We can go to the iconic CJ5

CJ7

And the problem with plastic valve cover

Is we're elephants and we don't forget

We don't forget anything

We hate them internal slave cylinder

Transmissions

Yes

Some reason

In the late 80's they thought

It was a good idea to make a plastic valve cover

And

They could have made it good

But we weren't where we are now

With plastic technology

First, A

Second

How many fasteners should a valve cover have

On it

Not two

In a spot that it's not reinforced

Yes

And then it's not the right kind of plastic

So it heats up and it starts to move around

And

It starts to expand

And then it starts to leak

Now the sad part is

Metal ones leak too

Because cork sucks

Cork gaskets suck

But I want to move

From that CJ5

CJ7 owner

But wait there's more

The

Renix era

Was yet again

Those damn Europeans

Touching my

American Jeep

And I had a closed cooling system

With a plastic bottle

We're coming for your vehicles

Yes

Which quality and

French manufacturing

Never was quite

Together

I think they did okay

No they did

I see you

And you did touch me

Intimately

In ways that I will never forgive you

But we had a plastic

It wasn't quite an overflow

But it's a closed system

And what didn't help

Because it's French

The caps were hard to find

They were also plastic

It was the 80's

You didn't have the interwebs

And the supercomputers in your pocket

Your dad

Grandpa that had a CJ

That was touched 14 ways

The Sunday with the valve cover

Was like that's a piece of crap

Because it's plastic and in the engine compartment

So then we

Slowly evolve and we get into the TJ

I did have a

Radiator

I remember where I was

The day mine exploded

It's a rite of passage I think

I was looking at a car trailer on the side of the road

And I heard

And I thought

What in the heck was that

And then steam started coming out of the hood

What would become Chuck Norris

And I thought

What did you just do with your hand

This

I got nothing

Jeff that's why you got to

Tune into the live so you can see what

What was that move

With your hand

Your verse octopus

Okay folks

That's what you get

When you get the visual

The reverse octopus

Don't Google that by the way

I don't know what that is

You should definitely do that on your

Computer for work

Anyway

So I then had to take the

Capsus

Not going there

And then I had to

Drive home

I was not expecting to put a radiator in it that day

Had to put a radiator in it

Was not happy

We all thought that was because

The mothership was cheapening out

And I'll go even

A layer deeper

We had

Three ones in GM world

Doing stupid

Heater core

Connections in plastic

That would snap off

At the threads

We had things with

3800s that were plastic

And were problematic

So I understand why we're beaten

And we're traumatized

When you say plastic in the engine compartment

But

Just like

Some things that we don't think about

Like pulleys have been plastic

For

Some pulleys have been plastic for 40 years

Right

And

The bearing itself

Internal to the pulley is metal

And what fails

What fails

The bearing

The plastic doesn't fail

Nope, the plastic does not fail

And we've had plastic

Bumpers

And those things

Doesn't mean we have to like the bumper

Cladding

There's plenty in your life

That is plastic that you don't think about

Because it hasn't wronged you

You're not like that

Eve or plastic

This is a great morning

If this is your first time

Joining this podcast

In your ear holes

I need you to know this is part for the course

So anyways

Listen more

I think there might be a few more accents

On this episode already than what we normally do

The normal? Yeah, that's probably fair

You haven't broken out the Minnesota accent

I have not felt a need

To offend the Minnesotians

With their fruit salads

Or those

Lovely beady-eyed Canadians

Oh, wow

You went straight for the attack

The accent isn't enough, huh?

No, it's just

The part that

It really shows that

The 3-8 JK

Really didn't offend anybody with plastic

Nobody gets up in arms about

There's a lot of plastic under there

Valve covers are plastic

Intake upper is plastic

Pulleys are plastic

Nobody gets upset about that

I really want to

Continue the trashing of the 3-8

In life as just a general thing

But yet

Exactly what you're saying

It had the potential to fail

On a number of fronts

And honestly the

Seal structures are the only thing

That oftentimes became its downside

I mean the biggest challenge

I think with the 3-8 is

You had people that had them in

Vans

And they just soldiered on for

Eternity for some reason

And the minute we turned them

A little bit

The other way they got angry

And they didn't last quite as long

In some situations

In other situations they again soldiered

On forever

And so let's not get

Too off crack

For example though we've had plastic

There and then

And we did not get so upset per se

Then 12 happened

And we thought we knew some things

We released a new motor

Spoiler alert

The valve covers are still plastic

Intake is still plastic

Lower and upper now

Instead of just the upper

And they decided we needed

Oil cooler because now we have

Dual overhead cams

It's now 1991

In Jeep World

Welcome to what GM

And well

Mazda and Toyota all did

In like

89 to 91

Because now you can get more first

Yes

With overhead cams

Our engineers just woke up

But change is hard

Nape said life is a pain, heinous

Anyone who says differently is selling something

Another quote from

Scott doesn't understand

No it's fine

So we get dual overhead cams

We get cams

We get all the cams

All the valves

Lots of moving pieces

And for some reason

We can't go back

You know like

Find the guy that retired from Mazda

And be like hey

And do it our own way

It's like Ford and the Bronco

They had no idea that a comparable vehicle

Had been produced for the last two or three decades

And they were like we're going to do it our way

So anyways this is now

We get an oil cooler

If you didn't understand folks

First of all I'm here to offend everybody today

Second of all

I can't imagine why that wind

Is coming in the side of my soft top

Yeah welcome Bronco owner

So we are specifically

Talking about oil coolers

And radiators

And those plastic components

That people focus on

And this is a perception issue

Because as you have already outlined

We have valve covers

And we do have upper manifolds

Which years ago

It's been that

Then they've been that way

In automotive production for 30 years

And I want to talk about

For a brief moment I want a side quest

Into

Cold air intakes and or just

Your air intake

Because

And again going back to the CJ era

We had

Kind of a metal housing

Which then typically had

A plastic snuffle up against tube

And again that plastic

Snuffle up against tube

Was almost too elaborate

It was a paper thin plastic

And it did not last

It was the 80s plastic

Correct again it was a bad plastic

For that time

And yet it did its job

Sufficiently for the duration

Of its rolling off the factory line

We went from those

Metal housings to

These plastic intakes

And we carried that

Your TJ had a plastic intake

It did

An air box

Why are we offended about that

And the problem is there was

A series of folks

Who ran out and replaced that

With metal tubes

Which is awesome for heat

Transfer

Metal transfers and

Holds heat

So if you look under your hood

And you have a metal tube

Connecting your air cleaner

Into your engine

Right now with a modern day

Vehicle

You're not helping your hearters

You're not helping your engine

You know what's really sad?

XJs had plastic air boxes

They did

Rubberish plastic to

Going to the throttle body

So we're talking

As old as we are

Correct and those plastic

Other than a degree

Of restrictive properties

That was of concern to

That tiniest fine

Tuning level

Otherwise

Realistically speaking that plastic

Disuppates heat

Better than the metal does

Disuppates or isolates

It has different

Thermal conducting properties than metal does

A thin aluminum tube

Will allow heat transfer

Faster and hold it longer

Which in general

Is bad

It brings up the temperatures of the air that your engine

Is taking in.

Engines are air pumps and they want cold dense

Air

9 out of 10 times

The best way to put it until they at the operating temperature

They want to be within their

Engineered operating temperatures

Any who's a what's it

Now let's head over to this

Daster

Miley offensive to

Minnesotians there

Got that one in

How did I offend him

Who's he what's it

So any who's

So we get into

The 12 we broke the mold

It's now 1991

We have

We have the 3.6 penistar

It's not actually 91

Just for those who are listening

It's it's factually

2011 pushing into 2012

Yes and 20 years behind

The behind the ball where I try

Some things we got a

You know r&d some

Stuff and

We we designed

Oil cooler goes down in the bellies

Of the motor immediately people were upset

That was like

One of 15,000

Things that they were upset about and that's with every

Model change

Or whatever

Changes hard

They like their push rods

They like their their old

School

Crank windows Jeffrey

Wrong with a crank window

So changes hard

Till someone comes up to your passenger side

To talk to you and you got to lean across

Throw the window down I know

I have a truck with the crank windows

And I don't like that

Anyway

It's going to convert all this crank windows

To electric even on the old school

It's really my number one gripe

About my international

I have to be honest with you

I'll be honest the international that would annoy me because you can't just reach across

You can't reach across

It is a long way

Let me throw it in neutral

Air brakes on unbuckle walk

Have a block as you said

Call them on the phone at that point

That's more convenient

The truck's so loud you can't like and it's tinted

So it's like they have no idea that you're

Desperately trying to talk to them

Alright

So and the biggest challenge is

We didn't really do the

Oil cooler well

In 12 and 13

If anyone

Has worked on a multitude of

Jeeps long enough

They have taken the oil cap off and then

Something has tried to poke your eye out

As it just exit over

Your shoulder

That's the oil relief valve

That's in the 12 and 13

They break all the time

There's a pretty decent spring on that

And it just

Yeets that across the shop

Most lube techs at that point

Pretend they did not happen and they just

Stuff the filter back in there

The other piece and I just have no

Faith in these lube techs

Specifically Jim Bob's garage

Did not know what to do

And this is my own

See the problem is they just came off the

Snap-on truck and they're broke now

But they bought the long handle ratchet

The long handle ratchet

And they got to use it

Spent like $300 on that sucker

And this is just

A hat's coming off he's getting worked up

I am worked up because

It gets me like my hair's on fire

It's like such a trigger because you know what

Half the complaint for people was

It has a plastic oil filter housing

And they crack

B.S.

So I actually found

Evidence

People adding

12 and 13s did

They cracked because the plastic changed

They actually were not the same plastic

That your current

From mopar oil

It's actually changed

Even that the majority of the times it was cracked

Is because somebody over tightened the cap

Well that's because they got the long handle

From stamp-on that was $300

But that's the problem

The plastic doesn't itself inherently crack

And even if it was a slightly weaker plastic

I think that it would have

Cracked less

Even if it was a weaker plastic

It would have cracked less

If these

Darn

If these darn loop techs

I'm trying to use nice words

Didn't use the long handle or use their

Uggadugga gun and go

Blah blah blah blah

To put the cap on

To talk from an engineering standpoint

The engineer that designed the oil cooler

Would have looked at the temperature requirements

He would have looked at the expected

Service life

He would have then went to his

Book or research

And looked at a proper plastic type

There is not just one type of plastic

There is up 10 million different types

Would have picked the best

For availability cost

And that would have

Utilized his things

He did not expect loop tech

With long handle ratchet

In that design

Or an impact wrench taking it on and off

That you've seen it done

So that's why

The first revisions happen

Also we realize

Hey, the thing trying to

Take your eye out, that's not a great plan

So by 14

That's phased out

They redesigned the filter

And this is where the conversation

I feel like we have to say

This is the nipple versus no nipple

Conversation and I don't mean

On Jeffrey's body

And we also have to talk about the

12s with the 530

Oil versus 520

Things were hard

Things were, we had head issues

There's lots of bad

Stuffage in 12

Because change is hard

Any who's, by the time we get to

14, 15

They really had kind of figured out

The cracking plastic problem

Aside from the guy that really got

The long handle ratchet

And most loop techs at that

Point had gotten scared

Of the tightening

And I've learned to be like, okay

Maybe I don't need to pretend it's

A 18 wheeler lug nut

I can just gently tighten

That up

But yet

More revisions happened

And surprise

Even in the JL

There is more revisions happening

And

Something we personally have seen

Is not your oil cooler

Cracking that is making it fail

It is the seals that are

Between the

Block of the motor and the

Oil cooler

And you could

If you love taking

Your intake off and on

Just replace the seals

We feel

That that is just not wise

That we might as well hit the reset button

Put a new Mopar cooler in there

And now we have reset it

And you should be able to go for

80 to 100,000 miles

Without interrupted service

What we see

Commonly

Almost every time we see one with

Aluminum cooler, guess what?

They still leak

Because doorman seals suck

So there's some people saying

Oh you know

Because the plastic has offended us

We have to go to doorman and get a cooler

Then we have to go over here to Mopar

And get seals that they've redesigned 14 times

Well guess what?

Doorman has not re-envisioned

That oil cooler of theirs 14 times

They have made it once

And we have seen it

Time and time again with aftermarket companies

Someone

Decides they have been wronged

By plastic and doorman

They're going to make an aluminum cooler

And then jobs

Change

Positions change, whatever happens

They are just going to keep making that design

Engineers

Have to sign

Basically agreement when you first

Start that anything you create

While you work there is their property

I've literally had to do that

Therefore just because

They're continuing to make that process

Or that product

Doesn't mean the actual person that

Conceived it and knew how

Every little intricate detail

Worked is still there

And then so when you call up and say

Hey, such and such happened

They're like I don't know dorge

I don't have no clue

And we've heard multiple times

That guy doesn't work here anymore

But we're just going to keep making it

Because it sells

Because plastic is bad

So it is important to know

Kind of in a statistical sense

That the

Oil cooler

Assembly

Is from

2011

To 2024

It is a direct interchange

Of those

Of the same oil cooler so we can take

An oil cooler that is currently being used

On a 2024

JL and in

Theory

We could use it on an 11

Now there is going to be a number of different

Parts to this conversation

Because of the sensor conversation

But there is a specific

Part that MOPAR lists within their catalogue

That is an oil cooler assembly

And

Likewise the doorman actually is

This it says it lists that it is good

From 11

To 24

And that doorman part

That you are referencing

Um has

Then a plug

Provision to cap off

Where the sensor

Because the holders

JLs have one

And then the issue is

That you would be retrofitting

Say that

That 2012

Jeep application

You would be retrofitting it to a

Nippled

Filter so now you would be using a

14 plus WL

110 Wix filter

You know what they should do

They should bring back the little sticker

That was on all the early 80's

Jeeps firewalls that said

Warning

This

Oil filter thread has changed

So Mishimoto

What I think is interesting is

There is a lot of chatter out there

About the doorman oil filter

But Mishimoto in my opinion

Is one of the ones who also came to market

With it

I have heard less

Now I suspect I hear less

Because

Factually again

That part number

That became relevant to the

2012 production Jeep JK

Has been revised

Nine times

That means that

Over the course of

14 years

14-15 years

Jeep Chrysler mother ship

Stalantis has

Found an opportunity

To make that part better

Nine times

Now

As Jeffrey has already mentioned

The later model JLs

Only require one sensor

Versus dose

So in theory

That could be a revision

Of itself

It would not necessarily be about

Oil passages

And galleys

But it could be about the sensor itself

But there is a conversation to be said

About efficiency

About seal structure

And how it sits up

Into the filter

Into the filter housing

Or the cooler housing

All of these things that as a

Multi-billion dollar company

They would have discovered

They would have made their product better

So the doorman aluminum oil

Clear was released in June of

I know

That during

And this is the

Neal thing

Somewhere in the Covid shutdowns

I remember seeing an all aluminum

Cooler start to get

Trickled out into the world on the Amazon

Yes

And I remember thinking

To myself yes this is going to be

A hot ticket item for a lot of people

Yes

And I don't know who made it

At that time

Like all good things made in China

Just because doorman has a

Rupple name it's still

Made overseas

And reverse engineered elsewhere

Yes and the minute you

Take your blueprints over and you hand them

To a Chinese manufacturing plant

They are copying

Now 10 manufacturing plants have it

And now you can get it on Amazon

For dirt cheap does the quality of it

Anywhere close

So that's the whole nature of it

Is that we have 9 super sessions

Of product

What specific

Variant

Is this all aluminum

Cooler designed

Around

And just because it was released in 22

Doesn't mean they used the 22 revision either

Because they had development time

They likely used a much older version

Of a couple years older at least

More than likely

And that's the thing

Is to say which one

You know and if they were willing

Or able to indicate

Which one it is or the improvements

They've made or the reverse engineer

That they put into it

They don't even know because that guy's gone

What's the other problem that I have with the

Doorman

Comes disassembled

You're having to assemble it

Versus the mopers already preassembled

Interesting

Now you've got a second fail point

Sure

And that's a good way for them to

Put the liability on to the

Consumer and the installer

Versus their

Monkey putting in the box

Alright well on that note

Says we're offending everybody what the heck

Wow

So Daddy Jeep said where your safety glasses kids

That was in reference to you

Ejecting

The coil

That's right

And then Nate actually

Purchased the doorman cooler

But he returned it on a recommendation

And that's because we've pulled more

Of the doormans out than we've

Scrapped a lot of those

And that's not to say and this is a challenge

That you know

I know we'll have the feedback on this

And people will say well

I put it in and I never had any issues

And that's fine

And you may not

And there's such a volume

Of these

Transactions happening

And I've driven two, three, six vehicles

And I've never put an oil cooler in one

Oh boy

And you know

The nature of

I had to put one in mine

Of course you did because you use it as a one ton

Yep it's fair

As far as the nature

Of these

These are concerned

There is such a massive volume

Being

Exchanged regularly

And so as we talk about

Who hasn't put them in their vehicles

Wait wait wait

Nate said that the doorman comes with

Orange filter housing so that's definitely a plus

I will paint yours orange if that's all

It matters

I don't think that's an upgrade

And this is what I was going to say

Is that you may have had a good experience

With yours and I would say

You may or may not know what you don't know

And that it is

Working sufficiently but could it be working better

We've certainly

Encountered what we feel to be

Flow issues with

Coolant passing through

The unit

Greg had one apart the other day

It's kind of interesting to me that

The oil and the

Coolant passages are actually crisscross

People might think that

They are parallel each other

But they don't they actually crisscross internally

And so up in there there's

All these different passages to

Allow that process to

Happen efficiently

And

I think that

In that the air could potentially

Get trapped or maybe a passage is too small

To allow coolant to pass through

Or is there a nice hefty

Mold line from the aluminum in there

That restricts flow

There's all those things

Have a potential to

Create more issue than

Than something else which is a conversation

We had about the

Radiators last week

About the flow rate

Or the flow nature of them

As far as replacement

One of the things that we're privy to

Is on a

National level

How many of these are being

Sold

By the

Stellantis

Network? Well real quick

Go ahead and go on to our live chat

Put in your guess

Correct and I'm going to

Shock and awe you with trying to say

What kind of plastics are used in engine

Well so while you are guessing

How many of these are sold

Weekly

Not annually, not monthly, not quarterly

How many are sold

Weekly

For replacement

In both dealership

Application and then

Authorized dealer

Distributor

So at a national level

So if you have an intake manifold

Or something of that nature

So engine cover

Intake

That kind of stuff

You don't see some heat but not

The pit of the fury

It's poly

Mide

Or nylon slash pa

Thankfully we have short cuts

Yeah we're doing this

I'm going to see it through

And I'm going to try to say the real

That was the easiest one

I know it is

So then we have

Poly

Thing

Sulfide

Which is pps which is hot zone

So that's going to be our oil coolers

That's going to be

Anything that's in

The fury of the engine

So anything that sees a lot of heat

Which

Quick sidebar

We just saw

Probably the most

Used

JL ever

Come through the shop

And their lower intake manifold had started to melt

And honestly that's not

Common

So when I was in college

Engineering college

They talked about poly

Set

And

See how was that

Basically one plastic you use heat

To set it and then it's set

It cannot melt

It actually burns if you heat it up to that

Temperature again

Because a chemical process happens

Which basically changes the

Molecules of the plastic

Then you have one

That you use heat to

Inject and that can be melted

Back down reused and put back

So basically think your milk jug

You can take your milk jug

You can shred it up

Melt it down, re-inject it

Use it for something different

I'm surprised

The intake isn't the

Thermo set where it's going to

Burn

Versus re-melt

But that is not what we saw

It was literally starting to melt down the center

Of the ports

Yeah, it's important to note

That that is actually something we've never

Seen before

In the grand scheme of life

It was an 18jl

It's actually not the most mileage we've ever seen

No, I'd say most used

Right, well, I mean

How much did it get to do that?

That's the concern

Now, we look at my wife's Jeep

Where I think we had a head gasket

Breach

Which is a whole other conversation

About multi-metal surfaces

Which wasn't plastic there

Not plastic, it's actually

A steel head gasket with aluminum

Block and head basically

And so

I don't exactly have a reason

As to why my wife's Jeep

Started to overheat

But

We eventually

Came to the fact that I had

A breached head gasket

And that'll be a podcast conversation for the future

Is breach versus blown

And with that said, you were ingesting a lot of oil

Into the intake system

Because of whatever was going on

And even with that high

And it didn't overheat

Is what I'm trying to get into

And the intake system

Plus the overheating

Your lower intake was fine

Correct

Mud does bad things

And I think that was the issue we saw in this

Is that the heat

The insulatory properties of mud

And just the

Heat soaked it

And kept that heat on that plastic

Intake where the plastic

Wasn't able to dissipate

The way that it was originally designed

Plastic should have cooled at a rate

And it held onto it

Which I think is what enabled it to melt

So anyways, so that was

PPS, which is what's used

On our really hot zone

Items

And then we get into the real kicker

Polyethylene

Tertone

Or that

Is also known as

Peek

Which is high stress

And they can also add carbon fiber

To that, so then you basically have a race car

I hear race car

And that is used for like

Oil pumps and anything that's going to be

In a high heat, high stress

And then something else that occurred

To me when we had all this conversation

Carbon fiber is plastic

Technically

And all of our

Supercar race cars have been

Some sort of carbon fiber or plastic

For most of the

Vehicle, like we're talking

The chassis that you sit in

That protects you from a crash

That's something that goes 200 miles an hour

Is plastic and that's okay

But if it's on my engine

It defends me

Sure, I mean I think that

That's exactly what the

Horse that we're starting to die

And we're kicking still

This idea that

Just because it's there

Does not mean that it should

Offend us. I think it was the take

Away and that's not to say

That there are not

Benefits to metal construction

If I go in my

Way back time machine and we go to

Bronze brassy aluminum

Bronze brassy radiators

That was a very good

Constructed radiator

That worked soft material too

And it was allowed to flex

Eventually it would thin and crack

Correct. With age

It was repairable. There was

A number of things that we found

Benefit as automotive

Enthusiast to having that type of

Construction property

And like we said before, we went to aluminum

And radiators because it was stronger material

So we could make the horse bigger

Better heat transfer

But it does not

Flex

And when it flexes

Is not as forgiving as

Correct. It's more of a brittle

Metal one to break

Look at the numbers here

That are coming in. We've got

Bradford saying 300 to 600

Bill McWilliam said buck 298

Okay

So as we talk about

This and the replacement process

And as Scott mentioned

We replace it

As a

Resetting the switch

The assembly

Because the other piece about that

Oil cooler assembly is

Again those passage ways

You know

They could have carbonization or build up

Because they are kind of thin

They're tight. It's like cleaning out an artery

At that point in time. Your degree of your

Triple bypass because the labor

Is pulling the intakes and pulling the seals

Which is also why we do spark plugs

While we're there. Correct. So

That's why we do the sensor

While we're there. You know what I mean

Because ultimately there's

Not a major

You shouldn't take it out of your old

Oil cooler and put it in your doorman

And put it in there. And we've seen that folks

We've absolutely seen that. And then we've

Actually seen that sensor fail

Because it was happy in its previous home

And then shortly thereafter it was unhappy

And then the Jeep ends up here

It's a service interval

Nate came in with 350

Weekly

Oil cooler assemblies

Sold

By the

Stellantis dealer network

So this is an authorized product

Is 3063

Weekly

Average. Oh that's all. Wow

So you're selling

Over

12,000 of these

Oil coolers monthly

That's plastic

Infused oil coolers. So you're one

Doorman or Mishimoto transaction

Has

Kind of pales in comparison

To 12,000

Monthly sales

Of these plastic. That simply means

That the volume of that particular

Component is en masse

Compared to whatever else is out there

And

Nate reused his oil sensor

He's gonna have to change that soon

Hopefully it works for a while

But it'll be great Nate

It'll be perfectly fine

So the nature

Of the volume

156,000 a year

Some of those are gonna fail

Right? Now the thing is

There's so so many of these vehicles

Out on the road. It is

A design element

Failure in itself

Right? The seals

Are specifically

The first and foremost

Failure

They are buried

Down in the internal one of the

Hottest parts

The bowels of the engine

Where all of the combustion heat

Transfer is happening

At these seals constantly

And then when they start to leak

They're subjected to

The corrosive properties

Of oil and coolant

And dirt and debris mixture

Yes, the seal is gonna fail

And then once it starts to fail a little bit

It's gonna fail a lot

And again, that is something else that

Mopar has re-engineered 14 times

And I have changed colors

A couple times to show you that

Most of the time

Because obviously we haven't taken apart

A 24 yet

But the current coolers

That we get from the dealer have an orange seal

The ones that you're taking out of your Jeep

Are black

And we're talking about

Derometer difference

We're talking about slight profile difference

They're trying to

Make this better and honestly

It's kind of a crazy thing to think of

But because the volume of this product

Is so high

They're therefore allowed to

I'm sure on an engineering level

To reinvest in this

I think it's important to note

You just said about the orange or the red seal

The red O-ring

That's only on some models

That comes with the black

And the red based on the model you're using

You're talking about the one that goes down into the block

Yes

I'm talking about the ones that are

Between the plastic and the aluminum housing

Gotcha

And this actually is gonna

Kind of take me into my

I hope my last sidebar of today's conversation

That

There is a concern or reservation

For me right now

Very real when it comes

To seal technology

In these engines

And availability

And again I touched on it

In a couple of previous podcasts

But I feel the need to bring it up again

That

The sealing plastics

That we see through Felpro

And Molly

And Victor Rines

And a new company

D&J

Which I'm not as familiar

But I do see their product more places

Than we have actually

Your OE application seals

You have five

To seven

Leading seal manufacturers

Who have all had to shift

Production over the years

Just like the OEs

From cork to rubber impregnated

You know gasket technology

To now rubber with metal

Rubber with metal

And then now to a more o-ring

Esk

Plasticy rubbery thing

That again heat

Environmental contaminants

There's a whole bunch of

Things that

I have some reservations

I feel as if we're seeing a lot of seal failure

Which

Factually I will tell you that seal failure

Is the number one leading cause

Of oil cooler replacement

And that's not just us

That's you

We've seen other mechanics referencing

That on the internet

Making videos about it

And can you imagine

If you would use

A sub-standard product like cork

For those seals how fast

They would fail

We gotta put in perspective a little bit

We're using a high quality

Gasket

That

Can last

80 to 100,000 miles

With relative general use

Obviously we're kind of

We see the more higher use

We're wheeling

We're letting our vehicle idle for all day

Heat soaking it more

We're putting in contaminants from mud

And water and

Debris

Into the engine

Because it is the V of the engine

All that stuff kind of goes down

And gets trapped in there

So of course we're going to see

A higher failure rate

Failure rate

But for a general bell curve

Of the society I think you can go

A long time without having a failure

And while you

They're still trying to make this product

Better again because they are invested

Or are selling so many

You're going to reinvest

In a product you're selling a lot of

Right and therefore

Ideally have it

Designed to the best possible

Practices that are available

I mean and I feel the same

We've started to encounter this

With again as we mentioned

Radiator technology

Again we've locked in

On radiators and

Oil coolers today

There's plenty of plastic from

Air intakes to

To actual intake

Manifolds, uppers and lowers

In most cases

Plastic

Not just in the engine either

You've got ABS sensors that are in the wheels

Where they get super heated in there

And that's plastic

That's plastic in the

Connectors for Rubicon axles

And axles get

Temperate and all of your sensors

Have plastic in them

To a degree gone are the days

You know a fully brass

Sensor or something

And fuel rails

Are plastic

Fuel lines are nylon

We don't talk about those as much

Because they're not as much

In our face as far as a failure

Is concerned but all of a sudden

When it comes to this

Hey the trash is in my backyard

Now I'm talking about

Radiator and oil cooler failures

Despite the fact that you guys just named off

A dozen items

That are

Plastic or have the capacity

To have plastic in them

And the plastic is not the fail point

Or the fail issue

The last piece that I do feel like

Is part of the world we're living in

Which is one of those kind of

Quiet aspects

Are the plastic connectors

The camming locks, the safeties

There are challenges

There

And no lock gets spread all over time

And it crumbles when you take it apart

The ACM lock

And that's another thing that we don't

As a consumer talk about

But those have cycle life spans

Yes

So if you unplug and plug it in

That is a cycle

And the more you do that

The higher risk of breakage you have

Because it's only designed for

I'll make something up

Like a hundred cycles

And heat

And age and use

Removes lifespan out of that

And one thing that

We're dealing with

Are the

As an industry

And again the average consumer might not be as aware

Are again these pigtail connectors

Kind of the specialty nature

Of them

The proprietary size and design

Last week alone

We ran into an issue

For

Our turn signals

For our JKs

And a lot of you out there have found it very fun

To put a cool

Aftermarket product in your turn signal

So whether it was a clear lens originally

Or now you got something from

An LED provider

And now you got a halo one

And each time you

Change out that turn signal housing

The pigtail wears out

Just a little bit more

The deep side pigtail

And that's not to count the times

That they side tap it

Or scotch lock it

Or whatever to add a function

To their headlight

And so now we have

Kind of diminished the lifespan

Or quality of that

Of that particular product

That pigtail cost us a hundred

Dollars

To replace appropriately

And you have to replace it

With its

Appropriate

Pigtail because

You're not just hardwiring parts

Together anymore

Because actually going into the

Turn signal is a proprietary

Shape and size

Then I went ahead and I found out further

That there's actually bad data

At the dealership level

So when you run it as a 16

You get the wrong part number

Yes, you get a pigtail connector

But it's the wrong part number

And so this is actually

Kind of a quirky situation

Back in the day this was

Not exactly our issue

Our wires just kind of went up

And hardwired into something

Or our plastic connections were far more rudimentary

Now as they become

More elaborate they have

Environmental seals to them

People are thinking

I'll just unplug it real quick

It's getting away

From that at this point

And certainly if you're a JK owner

You're cheap to tell you this

But some of you have

Almost a 21

Or almost a 20 year old

In your possession

That plastic has lived its life

A metal product

Would not have necessarily been better

Some type of other hardwired connection

But you have to be conscientious

About those things as you service it

And as you think about upgrading it

Going forward

I'm really excited

I hope to hear from people

Regarding what their experiences

Have been

What your feedback is

What did you think about

As plastic is relevant

In our Jeep production

As we're seeing more and more

Vehicle

Components

Produced lighter

With kind of better shape

And size

I guess I should make this last little tidbit note

Because this will be the

1% out there

You can actually

Go to the dealership

As Joe Average

You can go to your local dealership

And you can tell them

That you want to replace your oil cooler

And they'll bring up their parts

But I like that all-aluminum cooler

They will

Factually

Sell you an all-aluminum

Oil cooler

It will be an authorized

Mopar accessory

That is what it will be listed as

So of all of this

And again I'm not exactly trying to talk you out of the

All-aluminum cooler

I guess I know what our

Preference is

Yeah

It's fair

I have higher hopes for the Mopar

Factory one

You can

Factually walk into your dealership right now

And your parts guy might have to dig

A little bit

But he will find

A Mopar authorized

Accessory cooler

Which is a complete aluminum assembly

I need you to factually know

It is a doorman

It is produced

By doorman

It is a re-box

They put it in a Mopar box

There is a program out there

And I don't want you to get twisted

Thinking that all of a sudden

Oh hey

OE parts are the best parts

Mopar just saw the fact that

Hey there is a seam of people looking for this part

They're asking for it

So we're going to give it to them

We prefer to sell you this part

I understand from a business

I take the same standpoint

I prefer this part and I'll tell you why

But at the end of the day if you've convinced yourself

That this aluminum is the right part for you

I'm not going to talk you out of it

Mopar doesn't want to lose that sale

So they just literally sell you the doorman

It's a couple bucks more than if you were to just go on to Amazon

And buy the doorman yourself or go to AutoZone

And buy it yourself

But you feel better because you got it from the dealer

Dealers buy AutoZone in advanced

And

Insert here

Auto parts

And then just put them on their vehicles

So we're not trying to say that

That Stalantis dealer product is the end all be all

That's not the

The takeaway here

The takeaway is that plastic is not inherently bad

It's here to stay

And we have to learn how to relate to it

Change is not bad

Thank goodness it's not the plastic it was in the 80's

Thank

Thank the Lord

That is not those valve covers on the

258

Because of all those hard to say words I said

That was like a

I don't know what my laugh was at the end there

Alright with that said

There was a lot of conversation and I hope that

You found it beneficial or interesting

Or just downright offensive

I suppose that could be the case as well

And for that I sort of apologize

No you don't

We have a lot of jeeps to attend to

If you're interested in hearing about what's going on

In our personal lives we will

Expeditious about that explanation and share with you

What happened in this past week

Since we all got to hang out together last

So feel free to hang

Hang on through the outro credits

Until then jeep on jeep on jeep on

Thank you

About this episode

The crew celebrates episode 200 by tackling the “plastic under your Jeep’s hood” debate, tracing Jeep’s history of plastic failures from CJ-era valve covers and radiator tanks to TJ/JK cooling and modern oil coolers. They argue plastic isn’t automatically the enemy—often the real culprits are seals, over-tightening, service practices, and design revisions across years. A big focus is 2011–2024 oil cooler assemblies, why aluminum upgrades don’t always fix leaks, and how Mopar’s repeated seal redesigns matter more than material headlines. They also discuss plastic intake components, heat management, and connector wear.

4x4 all-aluminum cooler AutoZone carbon fiber cladding cold air intakes crank windows Engines are air pumps fasteners Felpro

Original notes

We want to hear from you, Send us a Text

Modern Jeeps use more plastic under the hood than ever before—and a lot of people hate it. But is it actually a problem? In this episode, we break down why manufacturers use plastic components in the engine bay, what they’re designed to handle, and where they actually fail (if they do). Not all plastic is created equal, and not all of it is a weak point.

Support the show

Thanks for listening, give us a review and check us out on YouTube -SFJ4x4 and visit our website to grab some great gear or products for your Jeep, SFJ4x4.com. Don't forget, you can email [email protected] for special content requests, blind react videos, suggestions, special guests, or general questions. Check out our Patreon patreon.com/ISpeakJeep

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