Plastic Oil Pans, Valve Covers, Misc. Parts

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On E39's like mine, the most pointed to failure point is the cooling system - frquently the plastic radiator, the plastic expansion tank, and the original plastic impellers on the water pump.

I had issues with one rear wheel well liner becoming incredibly brittle and disintegrating. It was on the RR where the fuel filler is. I've wondered if the occasional overfilling might have splashed on the plastic and degraded it (from previous owners, of course, lol)

IMO plastic is fine if it's spec'd properly for the application. Just like any type of material.
 
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On E39's like mine, the most pointed to failure point is the cooling system - frquently the plastic radiator, the plastic expansion tank, and the original plastic impellers on the water pump.

I had issues with one rear wheel well liner becoming incredibly brittle and disintegrating. It was on the RR where the fuel filler is. I've wondered if the occasional overfilling might have splashed on the plastic and degraded it (from previous owners, of course, lol)

IMO plastic is fine if it's spec'd properly for the application. Just like any type of material.

There's a difference between a composite oil pan and a radiator endcap that pressurizes and depressurizes each drive cycle and sees serious heat cycles while doing so and a composite oil pan that just holds fluid.
 
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Mercedes, BMW, VW have been using plastic tanks on the OE Behr radiators for 40 years and more, I have seen them still okay at 20 years and more leak free. Front end collisions even minor ones can twist the radiator and can cause it to leak at the tanks but brass tanks can also spring a leak.
I have a VW with plastic coolant elbows that are original and 22 years old, I will replace them when I do the engine this year. It depends on the material used, BMW has been using recycled plastic for some time and yes they has issues.

I would remove that pan sooner than later, there is a good chance the pickup/tube is damaged, A plastic one would probably have cracked.

If you think plastic radiator parts are good, you obviously have never had to maintain a Toyota.

At least the person with the metal oil pan made it home.
 
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My friend Mani hit a median curb hanging a U turn, pushing a metal part up and deforming the corner of her composite gas tank in her 2019 CR-V.
A good shop bent back the metal part with a 6' pry bar and told me the tank would likely pop back due to its memory.

I'll have to take a look next time I service it...
 
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When an uneducated tech, who hasn’t ever been an engineer, tells you that composites won’t hold up under stress, show him his picture of a composite structure that has been in service for decades. View attachment 83941
Salt water, extreme heat, extreme cold, G loading, carrier landing, catapult shots, all carried and endured by am airframe that is composite at its core.
Exactly. That guy spews nonsense like no other. Annoying accent too
 
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What is the reason and intent for using these plastic parts? Is it cost, weight saving, manufacturing ease, strength and durability? How durable are these parts? Have they been used for a while with good results?

Probably weight, the freedom to put it in almost any desired shape
and of course cost.
While I'd prefer aluminum in many applications for oil pans, valve
covers, water pumps and radiators including intercoolers, plastics
are ok in many applications and superior in some way to stamped
steel.
While the oil pan of my GTI is a two-piece design with the upper
half made of aluminum and the bottom part made of glass-fibre
reinforced PA 'plastic' that is shaped so that it doesn't retain much
oil when doing an oil change my Mini Cooper's steel pan does due
to it's non-ideal shape. I think it has been necessary to make it from
steel just because of the close proximity to the exhaust - it's just a
couple of inches. While plastics certainly have gone a long way they
surely don't resist elevated heat as good as steel. Of course its paint
doesn't. That's why the steel pan will rust which a plastic pan won't.

Plastic oil pans are somewhat new in comparison, they're used for a
decade or so. However plastic valve covers and water pump bodies
are used for several decades by now. In some applications they keep
up well, in some they don't.
.
 
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"Plastic" is an extremely generic name for many, many different types of composite materials.
True, but it's even more generic than that, because the term is commonly used for many different types of non-composite material, too. It's not composite unless it has non-"plastic" filler or reinforcing material added---although critical automotive parts often are indeed composites.
 

ls1mike

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What Kilmer thinks is worth next to nothing.
You beat me to it. That dude, well I will be nice tonight.

Lots of people call Nylon "plastic" every LS vehicle I have has a Nylon intake. Nylon 66 to be exact. They work fine.
 
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Astro14

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Scotty Kilmer hates plastic car pats too.
Not Durable.
Plastic parts on radiators is normally the failure point. Same with coolant elbows and water pump impellers, and thermostat housings.
That and metal parts don't get brittle with age and fall apart.
If Scotty hates it, then…what?

Metal parts don’t get brittle and fall apart? True. Neither do good composites.

But metal parts corrode, from oxidation and galvanic action, turning steel and iron into piles of rust and aluminum alloys into crumbling dust.

Quality parts hold up. Junk doesn’t.

Composite can be in either category. Just like metal.

Obnoxious, bombastic, screaming YouTube personalities oversimplify for crowd appeal. Scotty gets paid by saying inflammatory, often wrong, frequently stupid, things.
 

Astro14

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It's less than 20 years, even in Maryland and even if you aren't using the vehicle all that much.
I'm specifically referring to the famous Toyota / Lexus cracked plastic radiator tank.
I see.

When the solder corroded out of a brass tank and it had to be recored and re-soldered every five years, that was better?

I‘ve seen OEM brass radiators fail quickly.

I’ve got OEM plastic/aluminum radiators that are still original.
 
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