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2003 Jetta Whistling from the serpentine belt area

2003 Jetta, 2.0 engine, no turbo

The serpentine belt is whistling at high RPM’s when I press on the pedal, and it stops immediately when I let off the gas pedal. It’s coming from the serpentine belt, but the belt itself looks ok. I’m thinking it’s the tensioner or the pulley, but googling hasn’t been very helpful. There is no check engine light or any other light on.

What do you think?

Edit: I should have mentioned this as it is relevant, but the AC on the car has not blown cold in over a year. While driving the car, I put 2 and 2 together and remembered that the serpentine belt powers the AC compressor. Interestingly, if I turn on the AC the noise completely stops. For now I am just going to drive with the AC turned on, but I’m not sure why turning it on fixes the problem.

I think it’s time to get your serp belt and your tensioner replaced. :relieved:

Not sure it is possible or advised w/your particular engine, but one way I’ve verified a noise from a belt system is to temporarily remove it and run the engine briefly without it, see if the noise goes away. Be aware this may prevent the cooling system’s water pump from working.

A mechanic’s stethoscope might be helpful to isolate what’s making the noise too.

I think the advice given my TSM above is what I’d probably do first, if that hasn’t already been done recently.