Home » What Is The Most Egregious Engine Design Flaw You Know Of?

What Is The Most Egregious Engine Design Flaw You Know Of?

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Engines! We expect them to do so much these days. We want them to fling us around on our errands for hundreds of thousands of miles, sipping the bare minimum fuel all the while. That’s simply the bare minimum these days, but some engines fail to meet these demands in a grand fashion. This leads us to our question today—what’s your most hated engine design flaw?

Try as they might, sometimes automotive engineers get it wrong—and an engine ends up with a fatal flaw. Months or years down the track, a poorly designed part lets go, or wear hits some critical point. Suddenly, dealerships are getting bombarded with calls, forums are melting down with rageposts, and the automaker is left to arrange repairs via an expensive recall campaign. Or, hell, even buybacks!

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You would think that automakers would catch these problems in testing. After all, new engines and new vehicles typically go through millions of miles of testing before they ever hit the road. And yet, somehow, this still happens every few years, even to automakers with the best reputations for reliability.

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There’s a lot of bluster around the Cummins 6.7 and its grid heater nut, but many will tell you the controversy is overblown.

Earlier this week, we were talking about a controversial example—that of the Cummins 6.7-liter diesel. Listen to some, and they’ll tell you the engine will gladly ingest a poorly-placed nut, munching itself to destruction in the process. Listen to others, and they’ll tell you it’s an incredibly rare ocurrance. It might have never led to a recall, but it’s a compelling tale nonetheless.

GM was proud of its new diesel in the late 1970s, but it soon became an unmitigated disaster for the company.

Other situations are more cut and dried – for example, when Oldsmobile engineers tried to make a diesel out of an old gasoline V8. That engine had drastically underrated head studs that meant head gasket failures weren’t just a possibility, they were a near certainty. Because of that decision, many car buyers saw diesel as a devil fuel in America for the best part of a decade afterwards.

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Lancia Gamma Unholy Fail Ts2

You might also tip your hat to Lancia. The company famously built an engine so fragile that you could destroy it with a simple turn of the steering wheel. Properly Italian motoring, right there.

We love digging into weird engineering topics, and often it’s the quirky little failures that excite us—and you!—the most. So do tell us—what engine is your bugbear, and what is its fatal flaw that should never have made it to production? We’re absolutely dying to know what has your motor dying. Sound off below!

Credit: GM, Cummins, BMW

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Kevin B Rhodes
Kevin B Rhodes
23 days ago

The 379CI diesel V8 used in the Chevy and GMC trucks starting in 1982 was in no way related to the Oldsmobile 350CI diesel. It was designed by Detroit Diesel, and had none of the issues of the gasoline engine based Oldsmobile nightmare.

My family had several of them used to drag enormous campers around, and the only issue with them was the hydraulic brake boosters that liked to fail. And the fact that without a turbo, one had best not be in a hurry when towing 10Klbs of Airstream’s finest. I took my driver’s test in the second of them, an ’85 Suburban. Slow but steady.

There have been plenty of terrible engines – I don’t think it’s possible to pick just one. But GM is pretty good at making bad engines. They are fine as long as they don’t try anything new, but it seems like anytime they get creative it gets very bad, very quickly. The Corvair flat six wasn’t great, the Vega I4 was awful. The Cadillac V8-6-4. The Northstar. Countless others right up to the craptastic modern turbo I4s they are putting in everything today.

SCOTT GREEN
SCOTT GREEN
25 days ago

Water pumps that are driven off of the toothed-side of a timing belt in an interference engine. We had a ’95 Neon that destroyed the engine because the water pump seized up with no warning.

67 Oldsmobile
67 Oldsmobile
26 days ago

Any engine with cam followers that are bolted to the block. Those fuckers always fail eventually and then the whole engine is a mess.

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