Over the last 6 months my belt has slipped at least 10 times on my 99 xj. Needless to say im a pro belt changer now. Regardless im ready to drive my xj into a tree. Ive been damn good to her and im at my end here. Ive tried and tried to research jt to no avail. From what i gather it might be the crank pulley or harmonic balancer? But when i look at that it doesnt appear to be wobbling very much. However the place where the belt slips is right at the fan pulley. The belt will literally ride halfway on the fan pulley. I read it could be the fan clutch somewhere i think and i read to test it you spin the fan by hand if it doesnt stop spinning right away it could be bad. But mine stop right away.

 

Im thinking it could also be some bearings inside the fan assembly? I Would really appreciate any input as i am very frustrated with this issue.

 

Make sure that you have the belt tensioned properly and maybe try some squeal-reducing belt dressing.

It is also possible to put the belt on improperly and still have it fit. Verify that you have the belt looping through the pulleys properly. That is what it sounds like has happened based on your statement that the fan pulley is only half on.

 

It may just not be tight enough. People are often surprised at how tight the belt needs to be. But you also don't want to tighten it too much, so you need a belt tension gauge. Goodyear makes one called a "Krikit," which some NAPA stores sell. You can also order it from Amazon. It costs $15-$20.

The proper tension is 180 to 200 lbs. ft. for a new belt, or 140 to 160 lbs. ft. for a used one. Twisting the belt is NOT a reliable way to set the tension on a belt regardless of how many people tell you to set it that way. Use a tension gauge and set it correctly.

If it still squeals after you set the tension to spec, THEN go looking for other sources of the problem.

Also, next time you replace your belt, get a Goodyear Gatorback. They're made to grip better than a regular belt, even when they're not tightened all the way.

The fan clutch is not going to make your belt squeal. A bad fan clutch will make your temperature go up when you stop in traffic. And that spin test is not a reliable way to determine whether your fan clutch is bad. The only reliable test is to remove the fan clutch, lock the spring so that the fan is always engaged and see if that stops your overheating issue.

Unless you're overheating in traffic, put the fan clutch out of your mind for now.

 

I am pretty certain everytime it has been tensioned correctly as there was almost no deflection in the belt is was damn tight but not what i think was too tight. I will get some belt dressing and a belt tension tool. When i go to the store

 

Belt dressing is a good way to ruin a belt. Yeah it helps at first but then once the belt dries out again it will be louder than before. The oils in the dressing breaks down the belt over time.

 

I had this "Canned". Easy enough to try...(although mine was/is tracking fine)


Tight, tighter, tightest the darn new belt would still chirp.

Finally in desperation I went out there with a bottle of Dawn dish soap and the garden hose. Idling, I got it wet, then squirt soap on both sides, rinsed some, and soaped a little more. Let it idle a minute all soapy. To end, I ran the hose slow on it running for a couple minutes. Bingo! That solved it. There was some sort of coating on the new belt? Idk.

I normally run my belt as loose as I can, and still have the alternator not slip with the blower on high, and lights on brights. Puts less strain on all the other bearings. Radi pointed out a cool tip. After it might have been slipping, (voltage has been low), see if the Alt. pulley is hot. I want to go back and loosen it a tad now.

 

Do Not use the belt dressing! That stuff is made for the v-belts not the serpentine belts. It will only cause the serp belt to degrade.

 

Still having problems. I really think it has something to do with the fan pulley as its where the belt is slipping off. Will keep bumping thread until hopefully someone who's had this problem comes along.

 

hmnmmmmm

 

Ok, belt tensioned. You can take the belt off, check for any wobble or play in the main pullley( harmonic balancer). It is basically two pcs glued together, so if it's separating it might make a belt squeal. Also check to make sure the tensioner still has good range of motion, it sits in one place so they sometimes freeze up and stop doing what they are supposed to do. Both of those can be bought at the parts store and changed pretty easily.

 

I had a similar problem on my 85 with the 2.5L . I finally got to looking at my alternator and noticed it was sitting crooked compared to all the other pulleys. On my engine, the alternator is supposed to use three bolts to hold it on, short one on front top, short one in the back that attaches to a bracket attached to the A/C compressor and a long through bolt in the bottom. Mine was missing the through bolt on the bottom and when attempting to tighten the belt to stop it from squeaking I had let the rear bolt and bracket slide forward(it was loose at the top mounting point) and that let things twist until the belt would jump off the fan pulley.

Apparently the bottom bolt had never been installed and somehow the thing has been like that for nearly 30 years lol. I put a bolt through the bottom and it holds it perfectly straight now.

If you can stand to the side and see the pulleys, look at them closely and see if any of them are out of alignment. That will tell you where to focus to fix the problem. Could be the harmonic balancer if the two parts are beginning to separate. Any loose mount, worn bearing, or bent pulley can cause exactly what is happening to your belt.

 

If you are getting a squeal.........it's the balancer pulley slipping on the balancer hub.

Replace the harmonic balancer.

 

So i have basically also come to the conclusion that it is the harmonic balancer as well. However i think im buying an MJ tomorrow so will pass the info along to the new owner of this xj. Had it up to here with this xj to be honest. Best vehicle i have owned but its just been pissing me off since day 1 with small things breaking here and there and driving me crazy. New owner will be happy to know i fixed most of the issues the right way with the right parts but tired of the headaches.

 

what I did was on the pulley that the belt hangs half off I took it off and put some washers to space it out to keep the belt on it completely and never had a problem again. Sorry if I'm too late but too all you brothers and sisters who are having the problem there ya go. I remember I myself was able to change a serpentine belt at a red light and change it before green from the problem occurring so many times. Lol man if only you knew this one time it happened