Are composite or plastic engine parts that bad?

[XutvJet]

Originally Posted by Donatello.

The plastic crap on my E90 335xi was a joke. Plastic is bad & doesn't belong in a lot of places.

But how old was it when you started having issues?

[Efthreeoh]

I'll chime in. Just to put some creds out, I have a technical degree in manufacturing engineering (I no longer practice in manufacturing) and I've taken two courses in college on "plastics", I'm an old codger now with experience owning and working on cars from the early 1970's to 2022, and I keep my cars a long time and to high mileages. My oldest car at the moment is 27 years old, newest is 18 months. Over my lifetime I've seen the infusion of plastic parts in the engine compartment and other areas of the automobile. I'm all for it.

As many know, my 2006 E90 has racked up 400,000+ miles. Well documented here on E90 Post, it's really not had a lot of issues related to plastic engine parts. Modern cars with plastics in them last far longer and require far less maintenance than cars from 50 years ago (1970's); 400,000 miles on any car is impressive and indication of just how well-made modern cars are. Plastics are used heavily in cooling systems now because they work better. They work better because of chemistry. Antique cars with cast iron engine blocks, aluminum heads, and copper/brass radiators required extensive cooling system maintenance because there was a lot of cooling system corrosion due to the mixture of the various metals. Modern cars with aluminum core radiators and plastic end tanks last decades and multiple hundreds of thousands of miles. And the maintenance schedule is drain the coolant every 100,000. A 1970s car, if you didn't flush the cooling system every two years, the radiator core would eventually spring a leak, or a pin hole would form in an aluminum casting somewhere.

Metals corrode in cooling systems because of electrical eddy currents that run through the engine metals and water-based coolant. Using plastics greatly reduces corrosion.

[///MPhatic]

Originally Posted by XutvJet

Motors back in the 70s rarely made it to 150k miles, especially domestics.

I didn't say anything about Domestic trash. More research is in order for you sir. Many 70's Honda/Toyota engines made it to a million miles in the 80's/90's, and a vast amount of them made it to 300K+.

[Holset]

My S63 engine has aluminum valve covers but also a shitty plastic expansion cooling tank.

[cooolone2]

Guess the question avoids the Automobile mantra of "Built in Obsolescence"... Cars are not designed with the thoughts of "Longevity". Cost, Consistency, Profitability, etc, rule. But certainly not the worry that you might have to maintain your vehicle in order for it to last. They WANT you coming back for another vehicle as soon as possible. Not in 20 years!

That is all...

Besides, if it's is a "known" failure point, pay attention to it, do some preemptive maintenance and avoid the downtime experience with an unexpected failure.

Engines in the 70's lasted if you maintained them properly. But some maintenance items by today's standards could be considered a big job. Advances in technology, like metallurgy have allowed things to last much longer, handle more stress and such. The economy of the output of the engines, ie, HP per CU today is pretty amazing as well. This allows engines to do less work, leading to better survivability. All my opinion in working with cars and engines over the last 4 decades of my life, lol.

[BlkGS]

Originally Posted by XutvJet

Motors back in the 70s rarely made it to 150k miles, especially domestics.

You've clearly never heard of a small block Chevy or a big block.

[BlkGS]

Some things are OK for plastic use, but plastic is overall not as durable of a material as a good quality metal.

Vehicles aren't made to last 30 years anymore, most automakers wouldn't care that their cars didn't make it to 10 years until people stopped buying them because their resale value sucked so bad.

[Efthreeoh]

Originally Posted by XutvJet

Motors back in the 70s rarely made it to 150k miles, especially domestics.

That's because the body would rust out well before the engine died.

[Donatello.]

Originally Posted by XutvJet

But how old was it when you started having issues?

The car was less than 10 years old