Alright CF guys I got a bit of a mystery on my hands I was driving today and gave a little gas going over a hill and about 3 seconds later I realized that I no longer had power steering and I was starting to overheat. I pulled over and popped the hood I quickly noticed my Serpentine belt was loose so I tightened the Idler pulley back into place which fixed everything EXCEPT now with the pulley as tight as it can be i still have play in my belt which causes the most hellacious squeaking/squealing. So two questions what caused the belt to slip and will changing the belt fix the squeaking and everything?

Also It is a 99 XJ with a 4.0 and any help is good help.

Your belt may be stretched, It doesn't cost a whole lot to get a new one. I would get a new one and install it, then keep the old one as an emergency spare.

You could have actually over tightened it or the belt is just worn from being loose all that time. You should have a certain amount of "deflection" in the belt when it is properly tightened. I don't know the exact number something like 1" of deflection I think. I am sure somebody will correct me if I am wrong about the amount of deflection.

Try a new belt

Turns out my tension bolt sheared off I replaced that and retightened everything so its smooth riding thanks for the input and the damn auto parts store raped me on a new belt cost me 53 bucks

I had to order a Goodyear Gatorback belt --it was $33.00 but after all the squeeling i've been through and everything seems fine I figured I'd try some weird name one.

One more thing guys I'm new to the whole belt and pulley system thing with the bolt replaced everything tight and I checked all my pulleys to be true with just my power steering pulley slightly untrue I still have a major squeal when I crank her up and then for about 30 seconds after when I push the accelerator is this normal or is there possibly another problem I'm missing?

Are you sure that you have the proper tension on the belt?
If it is tensioned properly then I would try some belt dressing,apply it as per the instructions ex. with the belt off of the vehicle and wipe off any excess dressing. If that don't work try a new belt and make sure there is no play in any of your pulleys. In my experience the most common pulley issues would be with the idler bearing being bad and the water pump bearing going bad but done over look the other pulleys.

My jeep always seemed to sqeel always at the WRONG time. Early morn trying to make a getaway LOL..I just powerwashed the engine and she moaned and sqeeled a little afterwards but when all was dry she sounds much quieter than ever and NO squeel. I know its a Jeep thing to a point but I'm putting on my new belt tomorrow since its time and don't want to take any chances during the summer months. I usually keep thy old one as a spare just in case in the truck with my 150lbs of tools.

What would be the proper tension

I dont know the exact measurement but I did a quick search. Look HERE.

It is mentioned in that post that 1 half inch of deflection is correct for the year jeep mentioned in that post any way.
I am interested in the "90 deg method" for tightening the belt that is mentioned in that post as well.

Another method is to span 2 pulleys with a strait edge and using a ruler as a T in the middle push down on the belt and read the ruler against the bottom edge of the strait edge.

Are u positive u r adjusting the belt correctly? There's 2 bolts, loosen the bolt in the center of the idler pulley, then turn the adjusting bolt on the side, then re-tighten the center bolt in the idler pulley. We adjusted ours in very small increments 'till engaging the a/c compressor no longer squealed.

Alright guys I've readjusted my pulley so that the belt has the 90° turn and the squeal got slightly worse any help guys?