Intermittent belt squealing

1998 Cherokee Sport 4.0

Ok so for about a few months I have been experiencing this intermittent squealing noise which I think is coming from the belt. The strange part about it is that it comes and goes randomly. There is absolutely no consistency to when it occurs, meaning it happens sometimes when its hot or cold outside, wet or dry, etc. It is just really random. I installed a new belt (Dayco Poly Rib from AAP) a while back and that doesn't seem to have helped at all. The previous belt was a Goodyear Gatorback. I have tried several times to tighten/loosen the belt tension, but no matter what I do it makes no difference. It doesn't occur when the AC is on because the AC doesn't even work at all. One strange thing I have noticed it that if it is squealing and I press the brakes really hard and come to a stop the noise ceases. However, it can come back a minute or so later, or not come back at all until the next day or so. If it is squealing and I turn the engine off and back on the noise is gone. Also, sometimes if I accelerate quickly it will start to squeal. Some days I drive the car and never hear it. Other days it happens but it almost always goes away. As far as I can tell the noise is coming from somewhere around the alternator. But I do not notice any slipping or voltage loss when the squealing is happening.

If anyone has any ideas please let me know. This isn't driving me crazy yet but I'm getting close!

Have you tried using belt conditioner?

I just dealt with this on my 92.

1st removed belt and hand spun each pulley. All were smooth

2nd ran engine briefly with no belt. No squeal.

3rd looked at harmonic balancer. The rubber damper material was all dried, cracked and even sticking out a little.

Solution. New Harmonic balancer and quality belt.

Other common causes. Distributor bushing or carbon build up in cap/rotor. Power steering pulley out of alignment.

Be darn sure that belt is tight enough, as the 4.0 likes a tight belt. Tighter than any other engine I've ever had. That being said, you can overtighten anything. Krikit II is a good belt tension gauge that is available.

I'm not a fan of belt conditioner for serpentine belts. A little bit may have worked okay for the v-belts of old, but it can cause more problems than it helps with for serpentine belts.

And removing the belt and hand turning each and every component along the serpentine belt route always makes sense to be sure you're not chasing the wrong root cause here.

Are you sure the A/C compressor is not kicking on? Unplug the clutch wire and see if it goes away