Yet another serp-belt squeal thread

My 1993 XJ 4.0 has done about 120k miles. New water pump and serp belt replaced (with an OEM Jeep/Chrysler one) at about 70k miles.

In recent months the belt has started squealing. Seems to depend on the weather (damp/humidity?) more than anything else... It squeals more or less all the time - on startup and once the engine is warm, and whether a/c is on or off. Less audible, of course, when revving up, but always there.

But here's the odd thing: if I spray water on to the belt, it instantly goes completely quiet (for about 2-3 minutes, until it dries off). So during that time I can hear - or rather not hear - any squealing noises from the a/c compressor, water pump, or any of the pulleys. All these mechanical bits seem to be running smoothly and silently. And the belt runs straight and true: no sign that the harmonic balancer is degraded or out of line. The belt itself looks fine - no fraying or signs of wear on either the flat or grooved sides.

I've checked and adjusted the tension with a Krikit (and it's on about the 150 mark). I've sanded the smooth side of the belt so it definitely isn't glazed. Still the s-o-b squeals.

What else can be causing the noise? Do I have to assume it's just some weird problem with the belt, and replace it? I just hate having to replace parts that seem perfectly good!

br1anstorm

mine was doing that a while back due to the cold weather, i got some belt conditioner from CDC at work, (advance) and it shut it up and hasnt made a noise since. you might try that

Hmmmm - forgot to mention, I tried that too, briefly. Got some belt dressing and sprayed it on. Horrible sticky stuff. Worked for maybe half an hour, then the squeal returned. Then I went searching on the forum and found quite a lot of posts which said that belt-dressing is OK for V-belts but should NOT be used on the (multi-grooved) serp belts in the XJ 4.0. So I cleaned the belt dressing off with stiff brush and degreaser, and rinsed it with water. Now I reckon (a) my belt is clean again; and (b) that dressing stuff doesn't help..

Thanks all the same for responding. Any other ideas/experiences would be welcome!

put a gatorback on it

probably your harmonic balancer going bad.

craw underneath, look at the belt. have someone slowly rev the engine.

if the belt shimmy's at all, the balancer is coming apart like they all do.

I'd start by adding a little more tension and see if that does the trick... It might completely fix your problem.

Here's a thought, I've gone in with some good squeak juice and spray it in the nooks and crannies of the pulley's and bearings, ac, etc. If you've checked tension, water pump, fraying etc, have you looked at the bearing that the belt ride's across that is bolted near your ac? But use the spray first with the attempt to locate the squeak.:thumbup:

check you're ilder pulley brg. take the ilder brg. off and inspect it over. I had a belt squeel come and go. replaced the ilder brg. noise went away.

Jess said:

put a gatorback on it

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x2

gatorback solved my intermitent A/C squeal and it was like $2 more than the crap duralast belt I put on first

Did you inspect it closely for glazing? (shiny streaks). I have had pretty poor luck with lesser quality belts on the Jeep 4.0. Like others mentioned, I use Goodyear Gatorback belt only on my XJ.

You can try tightening it a smidgen more (4.0 belts really do need to be tight; tighter than any other vehicle I've ever owned)

BUT, You have 50k on this belt. I'd replace it.

BTW, skip the belt dressings on the serp belts.

went through exactly the same thing 2 months ago on my `92,water and all. lossen the necessary bolts on th ps pump,have the socket/extension you need to turn the adjuster bolt ready to go,crank the truck and tighten the belt until the squealing stops.these belts have to be crazy tight.

belt dressing usually just makes a mess.

might want to unplug the electric fan while you do this if your body parts are really close.

With that many miles on the belt it is probably time to replace.

Remove the old belt, use braker cleaner on all the pullys for good measure (or any other cleaner, simple green, whatever....except rinse afterwards) and then reinstall a new belt, preferibly anything but a Duralast belt.....Gatborbacks are sex! If you were local I'd give you a belt, I have 2 spares in my toolbox.

1994sport said:

probably your harmonic balancer going bad.

craw underneath, look at the belt. have someone slowly rev the engine.

if the belt shimmy's at all, the balancer is coming apart like they all do.

Click to expand...

I've never heard of this. My belief was that bad harmonic balancers tossed belts not made them squeal.

When a harmonic balancer starts to separate, it WILL squeal a lot.

He did say he put a small amount of water on the belt and it quieted down. If it was indeed a small amount of water only aimed at the belt I think this would rule the harmonic balancer out of the equation.

I had problem with a duralast belt once constantly squealing, belt dressing made it worse, and water quieted it down temporarily. Of course the belt got coolant all over it after the radiator blew, so anything like that getting on the belt usually warrants replacement. I tried to clean it with no luck.

Boatwrench said:

I've never heard of this. My belief was that bad harmonic balancers tossed belts not made them squeal.

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The squealing starts first, then it eventually tosses the belt. Or it might just skip step one and go to spectacular failure.

The balancer starts to come apart, and the pulley gets out of alignment. Once that happens the belt starts to shimmy and squeal against the sides of the pulley.

Happened to me, and a couple of people I know. I actually then got a bad balancer from the parts shop that was out of alignment, and had to take it back. Put #2 on, and everything has been fine since.


Tightening the shit out of it may temporarily cure it. It will also accelerate bearing wear on everything attached: waterpump, power-steering pump, alternator, ect.

The belt really shouldn't be he-man tight, if it needs to be to stop squealing, then you probably have an underlying problem.

1994sport said:

The balancer starts to come apart, and the pulley gets out of alignment. Once that happens the belt starts to shimmy and squeal against the sides of the pulley.

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bougtht an xj in otherwise perfect shape. saw the HB was coming apart, and couldnt figure out why thehub of thebalancer stuck so far out - if the outer part was lined up with the hub, the belt would not run on it. when I went to pull the old balancer off to change it, found that previous owner had been slowly pulling the balancer hub out to prevent the outer part wearing into the timing cover. there was hardly any thread holding the hub on ( it was hand tight) and the sealing surface was only about 1/4" into the seal......Yay for idiots

ps when put the new balancer on, started squealing immediately - was the belt on the paint of the new balancer

br1anstorm said:

...edit...
I've checked and adjusted the tension with a Krikit (and it's on about the 150 mark). I've sanded the smooth side of the belt so it definitely isn't glazed. Still the s-o-b squeals.
...edit...
br1anstorm

Click to expand...

Well, that quote was from my original post, and now it's time to bring this thread full circle. Guess what: the belt has stopped squealing. I haven't done anything more to it. I think the explanation must be that, after I checked and tightened the belt using the Krikit, it took a couple of weeks and 80-100 miles to settle in at the new tension - because now it's all peace and quiet again!

Not sure quite what that proves. Maybe that you can't always expect instant results or instant cures. Anyhow, it's one less problem to worry about. Thanks to all who offered advice - I hope the thread will be useful to others with similar problems in future.

br1anstorm