Automakers are quietly replacing critical engine parts with plastic
In my shop days, which ended in 2020 when I dove into media full-time, one of the more common critical leaks we saw was cracked engine coolant tees. These are the “T”-shaped fittings that join rubber coolant hoses. It’s been happening for a long time, now. Over the last 15-plus years, many foreign and domestic brands joined the cost-saver bandwagon and switched from metal versions to plastic: At least 14 BMW models, any Dodge/Chrysler/Jeep/RAM with the Pentasar V6, Fords with an EcoBoost or others, and virtually all GM SUVs and large sedans. Oh, and VWs and Audis, too.
We’d end up pulling out the cracked and bleeding plastic versions and replacing them with aftermarket metal ones. Order from the OEM, and you’d get another plastic one. By going with our brains and hearts instead of the factory catalog, we’d permanently solve the design issue and the customer would never have that same (otherwise inevitable) leak again.
You’d think over time, customer complaints and reliability ratings would convince engineering teams to go back to metal options.
Now, though, plastic is even more common…and it’s still being installed in some pretty unexpected places, like engine oil systems.
Nissan Rogue
Newer Nissan Rogues have plastic oil pans instead of metal ones.
Chevrolet Silverado & GMC Sierra (5.3L & 6.2L V8)
Many newer GM trucks have composite (plastic) intake manifolds and plastic valve covers.
Ford F-150 (3.5L EcoBoost and other engines)
Ford has implemented plastic oil pans on some versions of the 3.5L EcoBoost and 2.7L EcoBoost engines.
Dodge Charger & Challenger (5.7L HEMI and others)
Many HEMI-powered Dodge vehicles use composite intake manifolds and plastic valve covers.
BMW (various models)
Many BMWs now use plastic oil pans, plastic intake manifolds, and even plastic timing chain covers.
Mercedes-Benz (various models)
Similar to BMW, newer Mercedes vehicles have moved to plastic oil pans and composite intake manifolds.
Honda Accord & Civic (1.5L Turbo, 2.0L)
Honda has switched to plastic intake manifolds and plastic oil filter housings.
Toyota Camry & RAV4 (2.5L & other engines)
Toyota has moved toward plastic intake manifolds and plastic thermostat housings.
So what?
Well, to most drivers, the switch from metal to plastic is just a big “shrug.” But to insiders, it indicates a certain shift that might spark certain emotions…sadness, even. When it comes to automotive engineering, though, things are always changing. As they say, “Change is the only constant.”
As car makers aim for lighter, cheaper, and more efficient designs, engine component durability concerns and heat resistance remain key challenges. Cheaper, lighter stuff might break easier and doesn’t last as long. Such is the way of the manufacturing world.
If a plastic part in the engine bay carrying coolant or housing oil cracks, and the driver doesn’t realize it in time, the engine could fail. These days, engine failure often totals cars, since cars depreciate so quickly.
What’s more, automakers have already long been putting plastic inside the engine…to the abhorrence of mechanics and their customers. Many brands switched to plastic internal timing components years ago, which has led to timing system failure on countless cars that otherwise would have chugged along without much issue…at least not from cracked plastic.
On the other hand, cars are generally safer, more efficient, and more reliable than ever before.
The average car on American roads is 12.6 years old. I’m sure certain folks were sad when bumpers switched from metal to plastic, too. But the replacement front end design is unarguably safer with a steel reinforcement bar, foam absorber, plastic bumper cover, collapsible steering column, and the barrage of airbags front occupants meet on impact. I can’t say the same about touchscreen infotainment, though…I’ll probably remain a begrudged Luddite on that “upgrade.”
