1995 f250, 5.8 and driving me crazy! I replaced the belt and that worked for about 200 miles and now it's back. Sometimes you can hear it at idle, sometime not till about 1,000rpm. Sometimes {but not often}, you can't hear it at all and other times it's all you can hear. Sometimes it just abruptly stops squealing all together. I'm thinking it might be the auto belt tightener? Anyone with any input? Thanks.

 

i think someone in a different forum on here mentioned a pulley being bad, but i dont remember but i know i saw a similar post somewhere else before

 

Check the idler and tensioner pulley bearings. One (or both) of them is likely to be the source of your squeal.

 

I had the same issue on my 95 f150 5.8 about a year ago. Idler pulley was shot, belt tensioner pulley was shot, replaced both and still squeeked. When watching them as engine was running noticed that smog (air) pump pulley was intermitantly locking up and causing belt to slide across it and get hot and smoke a little. Replaced that and no problem since. Good luck.

 

Make sure all pulleys look / spinning fine
Make sure tensioner is working good.
Get a gatorback belt..

 

Also, make sure all your pulleys are clean as well as rust- and moisture-free (no fluids leaking onto the belt or pulleys anywhere). DO NOT use belt dressing! Use NON-CHLORINATED Brake Parts cleaner, spraying everything down really well with it (may squeal in the process, but should clean off contaminants).

Jason