So i just recently replaced the serpentine belt on my 4.0L XJ, and now every once in a while when I turn on the A/C or fan, I hear a loud screeching sound. I'm guessing the belts a bit loose and is slipping, which causes the squealing sound...is it possible to overtighten the adjuster bolt on the p/s pump bracket? I thought it was on there pretty good...

 

tighten it more...

 

Had a pretty knowledgeable mechanic tell me to just tighten it until it stops squeeling. Unless its cracked and very old, then you will be fine.