Here's the Real Damage Done By Letting Your Engine Overheat

One look inside this Audi S5's engine reveals just how devastating overheating can be.

Inside of an engine where coolant mixed with oil.

Christopher Smith

By: Christopher Smith

May 5, 2024 at 9:00am ET

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If you're reading this, you probably know engine coolant and oil should never mix. The coolant effectively negates the lubricating effects of the oil, which subsequently negates the engine's ability to keep running. That's what happened with this turbocharged 3.0-liter Audi V-6, which was still largely new when pulled from a 2022 S5. Now, it's a mechanical lump filled with an oil-coolant cocktail that resembles a chocolate milkshake.

surprisingly, the damage within this nearly new engine is relatively minimal. The exact mileage is unknown, but as this I Do Cars teardown video shows, the various components come apart with ease. Furthermore, there's very little wear and tear. The main bearings, rod bearings, camshaft lobes, and even the cylinder walls all appear in relatively good condition. Considering the engine was operated with compromised oil, this comes as a surprise.

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So why was this engine deemed junk? According to the video, a coolant line failed at some point, overheating the engine enough to warp the aluminum heads. That led to coolant mixing with the oil. The wear suggests it may have just been turned off rather than locked up, but in any case, the heads are toast. It's possible the top of the block could have issues as well. The damage is repairable, but in this instance, a full engine replacement was performed.

And according to the video, the replacement wasn't covered under warranty. The host says Audi denied the claim because the engine was overheated, leading to a $30,000 repair bill for the car's owner. So keep that in mind should you find your engine is running a tad warm. Pull over, let it cool, get it towed, and do whatever it takes to keep it from overheating. It could prevent a minor hose repair from turning into a major financial gut punch.

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