Hey guys. For the past few weeks, I've been hearing an odd noise from beneath the hood of my 99 non-turbo S70. It starts when the car's been on for a few minutes and continues whether I'm driving or idling. It comes on whether the air compressor is on or not. It's a high-pitched, whistle-like noise from the passenger side. It continues for a while, then stops. If I turn the car off, the noise stops and doesn't start up right again if I turn it back on. What could this be?

Sorry about the lousy description, I'm not as good with cars as I probably should be. Thank you very much for reading.

 

When was the last time the timing belt was replaced with the rollers? Idler and tensioner roller? When those rollers loose their grease the bearings squeal. If that is it, they are nearing failure and will cause your timing belt to break or jump timing if one of them fail.

I had the problem with my 960. Started doing it only when the car was cold, then a little more before I caught it. When I pulled the belt off the idler was so messed up that it took two hands to turn it. It was almost seized.