RAY MAGLIOZZI

Dear Car Talk: I have a 2017 Lexus GX 460 with about 90,000 miles. My car has been making a squealing noise ever since I had the serpentine belt replaced. The noise lasts anywhere from a split second to a few seconds, and it only happens after the first start in the morning.

Another mechanic told me it might be due to the aftermarket belt, so he ordered a Lexus belt and replaced it for me. The noise is still there. He told me the next step would be to replace the pulley and the tensioner. But he said the noise does sound like it’s from the serpentine belt.

Any advice would be greatly appreciated. — Chun

Have you tried a set of the Apple AirPods 3 Pros, Chun?

What you describe sounds like a classic belt noise. The reason it makes that squealing noise is that, for a second or two, it’s slipping. So, when you start the engine, the belt is supposed to start moving immediately. And for some reason, yours is not. The question is, why?

Here’s how that belt works: When the engine starts, the crankshaft, inside the engine, spins. At the end of the crankshaft is a “crankshaft pulley” that drives the serpentine belt.

Now, why is it called a serpentine belt? Because it snakes around a variety of pulleys that run a bunch of other accessories — the alternator, the water pump, the power steering pump, etc.

So, my next step, if your car were in my garage — and I’m grateful it’s not — would be to remove the belt one evening, and then, in the morning, when things have stiffened up, try to manually spin each pulley separately. Each accessory has its own pulley, plus there are idler pulleys and the tensioner.

Every pulley that the belt snakes around should turn very easily. It should offer little to no resistance. So, if, for instance, he discovers that the water pump pulley is a little harder to turn than the others, that may be the pulley that the belt is slipping over first thing in the morning.

It wasn’t a bad idea to try an original equipment belt. That was worth a try. And your mechanic is right to be thinking about pulleys. But I wouldn’t go replacing any of them until you first try to figure out which one it is. He’ll find it, Chun.

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