Tyler Posted January 20, 2021 Share Posted January 20, 2021 (edited) Have been having this issue for a while now. Belt will not stop squealing like crazy. When I mount the belt, squealing will stop for a while. Then it will return, seemingly from the water pump pulley. As the belt spins, I’m nearly positive it is moving forward slowly off of the water pump pulley, as it doesn’t seem to line up perfectly after a few rotations. Not 100% sure that’s the source of the sound, but nearly positive. 3rd belt replacement in hopes of that being the issue, mounted the most expensive one I’ve found on SummitRacing. I have tried belt conditioner (I think that stuff is worse than it is better), cleaning the pulleys, and even a bit of deodorant on the belt only silences it for a few minutes. Caused it to slip off the water pump pulley once, so I quickly turned the truck off and replaced it. 1990 MJ 4.0 Any help appreciated, thank you. Edited January 20, 2021 by Tyler Added engine and vehicle info. Link to comment Share on other sites More sharing options...
87MJTIM Posted January 20, 2021 Share Posted January 20, 2021 Sounds like you need to check the pulley. Make sure everything is properly aligned and that the bearings aren’t bad before you swap another belt. Link to comment Share on other sites More sharing options...
jdog Posted January 20, 2021 Share Posted January 20, 2021 Have you checked the harmonic balancer? Also 4.0 or 2.5? Link to comment Share on other sites More sharing options...
BeatCJ Posted January 20, 2021 Share Posted January 20, 2021 Or something else isn't out of alignment. Harmonic Balancer, crank pulley is a common one to move some when they start going bad. Link to comment Share on other sites More sharing options...
Tyler Posted January 20, 2021 Author Share Posted January 20, 2021 Just now, jdog said: Have you checked the harmonic balancer? Also 4.0 or 2.5? 4.0, I’ve heard to check the harmonic balancer. Gotta give that a look Link to comment Share on other sites More sharing options...
jdog Posted January 20, 2021 Share Posted January 20, 2021 6 minutes ago, Tyler said: 4.0, I’ve heard to check the harmonic balancer. Gotta give that a look Pretty common Link to comment Share on other sites More sharing options...
SVPete Posted January 20, 2021 Share Posted January 20, 2021 Absolutely check to see if the harmonic balancer isn't starting to separate and rubbing on/cutting into the timing chain cover. I personally experienced that with my Cherokee. It certainly will cause a squeal. Belt dressing is garbage (another personal experience and opinion). Tried that on my Comanche with a new belt that was squealing/chirping. It seemed to be eating the belt. Cleaned the idler pulley, bought another belt, and tightened the crap out of it. That solved that little issue. Couldn't sell the belt dressing at multiple garage sales for 10 cents or even give it away for free. Ended up donating it to the local Goodwill. Link to comment Share on other sites More sharing options...
SVPete Posted January 20, 2021 Share Posted January 20, 2021 Certainly check all the pulleys while the belt is off. Grab them and see if there is play. Bearings squeal too....Had that with an alternator and AC delete pulley. Belt coming off does sound like an alignment issue. Might want to see if the bolts for the water pump pulley aren't loose. Link to comment Share on other sites More sharing options...
WahooSteeler Posted January 21, 2021 Share Posted January 21, 2021 x4 on harmonic balancer. Definitely check pulley alignment first and pulley bearings, but the HB seems to be the most common source. How tight are you adjusting the belt? 4.0s need it pretty tight, do a search here on that also for guidance. Link to comment Share on other sites More sharing options...
Dzimm Posted January 21, 2021 Share Posted January 21, 2021 Definitely check over everything to make sure there is no damage and everything is straight. Make sure you get the belt really tight, the 4.0 belt needs to be tighter than other vehicles. Should only be able to get a max of 1/4 twist in the belt with your fingers. The belt on my XJ squealed for about a month after I took it off to do some work. Belt dressing always seemed to make it worse but after 10 mins of running it got better. Eventually it finally quit for good. Link to comment Share on other sites More sharing options...
AZJeff Posted January 21, 2021 Share Posted January 21, 2021 Belt dressing is NOT recommended for serpentine belts, as it actually makes the belt MORE prone to slippage. Link to comment Share on other sites More sharing options...
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