Driving home from work, I was slowing down at an intersection, and an extremely loud, low pitch squeal/whistle came from under the hood of my car. At first I thought it was the brakes of a car around me squealing, but later found out it was me. It is not the brakes as the noise varies with acceleration or revving the engine if in park. Tried to recreate it with the hood up and someone revving the engine and it is definately coming from the belt side of the engine. The serpentine belt did not feel loose. I presume the alternator to be okay as the battery light did not come on the dash. Water pump is not even a year old. Any other ideas?
You may have a worn pulley bearing which you can locate (IF there is one) yourself after removing the serpentine belt.
Starting with the belt tensioner pulley, turn by hand with a slight side pressure.
If you hear/feel a bit of grinding that may be the fault.
BUT, check them all while you’re at it.
Also while the belt is off, use a straight edge and check that all the pulleys are in line with one another.
Do not ASSUME the alternator isn’t the culprit as if the pulley bearing is wearing out, it won’t show any warning light until it seizes up and the belt flies off.