Damn thing is squealing and driving me nuts. I replaced the belt, and the idler, to no avail. The bearings in the idler were shot, but still no luck.
It stops when it's warmed up too about 190, so right as the thermostat is opened.
I took the belt off, and the alternator pulley squeeks a bit when turning it by hand, although, when the belt is on and running, a bit of soap on the belt quiets it immediately. Leading me to think its the belt and not a wheel, but its a newer belt, and it has to be a wheel slowing down the blet right?
My zj 5.2 has never liked certain types of belts and will always squeal if i put the more expensive belts on mad from the newer style compounds .The worst was a belt made by/for prestone .But As long as i stick to the old fasioned rubber/cloth type constructed belts - no squealing .
I'll guess water pump if it stops when the thermostat opens.
I just replaced my entire tensioner assy with a Gates unit. Really was making a racket near the end. But not a squealing, more of a clacking. Try shooting WD-40 into the tensioner and see if you get a change.