Last sunday i ran over a mud puddle. Figured that it was time to get the car washed anyway since i might as well get the engine bay area cleaned. I had some trouble with the idler pulleys since they were making these "whirr...squeak...squeak...whirrr" sound. its kinda sad to drive up and lets the public hear your car sounding like it had a mouse orchestra under the hood.
Anyway, i had the belts and tensioner checked out before i got the car and the shop said that there were in excellent condition. so my last option was to take a look at the idler pulleys (all three of them). The mechanic took a car stethoscope (?) to trace for noises and told me that the bearings in the pulleys were probably shot and that i need to replace them. So money in hand, i was ready to get some new bearings or pulleys.
That's when it rained, i ran over the mud puddle on the way to get the spares. Said i better get them tomorrow.
Guess what happened when i got the engine bay washed at home? The squeaking stopped!!!