I have a squeaking sound that comes intermittently. It sounds like a slipping belt, but I just changed the Serpentine belt, and the sound is still there. It sounds like it is coming from the top of the engine, maybe the alternator? It also only seems to come around when it is warm out, or I have brought it higher in the RPMs. Anybody have any ideas?

 

Try taking the belt off and run the motor for a short time this will help isolate the noise.
Might be the idle pully..

 

do you have UDP's when I changed my pullys out I also got a gatorback belt, it sqealled like a pig, i put the stock belt back on and it went away.

 

It still does it with the new belt, and it is a different brand.

 

How much does it cost to replace an idler pulley, and is it something that I can change myself?

 

Not sure of the exact cost cant be much, deffiantly something you can handle.
If that is it.

 

Its the only thing I can think it could be. Are there bearings on the inside of the pulley that could go bad?

 

check to make sure all your pulleys are on tight, it may be your idler...but for some reason i keep thinkin water pump pulley...just check all pulleys...im sure turning one of them you should find the source of the squeeking when tightning down pulleys...good luck