Alright so I have a 99 cherokee, and just within the last week I have developed a horrible squealing sound when I turn on my jeep. It lasts literally for like 20 seconds then goes away immediately after. However when I use my heat or ac it comes back for a few minutes and then goes away while cruising and comes back when stopping or going faster. I examined my belt and my tensioners and they seem fine. Actually I replaced my alternator with a band new one about 2 weeks ago. I know that the belt is tight, and the belt is good. Like I said the tensioner looks good and spins. Am i looking at replacing my water pump? Or should I look into a new belt?

 

Why not just tighten up the belt tensioner and be done with it?

 

It sound like your belt isn't tight enough. Pick up a belt tension gauge. the belt has to be really tight, tighter then you would think.

 

I'm generally happy that the Peep will start, a squeel would just be a bonus. I too get a squeel in the morning, dew on the belt. Don't go crazy with the tighttening, just snug a little at a time. Also check underneath and make sure your harmonic balancer is not failing, my outer ring moved rearward and was rubbing on the chain cover. I chased that squeel, new belts, different tensions, new idler, new idler bearing, tore apart the alternator, still squeel, found the balancer problem after 3 months. Worth a look.

 

I honestly dont think its my belt tension becuase I have tried tightening and tightening it with no luck, its at the point where im afraid that if I go a whole bunch tighter it might break when im driving. Ill look into the balancer though

 

I have also heard that some people get a squeal when their water pump starts to go bad...thoughts on that?

 

 

If the belt squeals when you turn on the AC you could look at the AC compressor and make sure its in good condition.

 

well I have not actually had the ac on, it really hasnt been hot enough for ac yet but I did notice it for sure when I turned any sort of heat or just air on for about 30 seconds. I thought the blower motor was not part of the serpentine system?

 

Just to let you know you AC compressor does come on when you turn on you heater.
I have my belt making noise when I first turn on my XJ if the AC is on. But if I wait until the belt heats up then turn on the AC it doesn't make any noise.

 

okay I didnt know that the compressor was on with any air (heat or cold).
It doesnt seem to matter if the engine is hot or cold it still seems to squeal for a bit. It also squeals when I start my engine, for a few seconds. It used to only do it when it was colder out or raining, now it does it all the time.

 

BTW, What ever you do DO NOT USE belt dressing on the serpentine belt.

 

Not quite - it comes on when defog is selected. So if air is blowing up on your windshield, and a vacuum problem isn't preventing the other modes from working, this is normal.

Pulleys can cause squealing like that indeed. One way you can check is getting up there while it's squealing with some WD40 and hitting the various pulleys, see if it stops for a bit.

Your belt might be on it's way out anyway. I've seen people recommend the Goodyear Gatorback for the 4.0L. Regardless these engines need their belts unusually tight...

 

Have someone start it and turn on whatever it takes to make it squeal and start trying to pinpoint the sound. Now with some many things so close together it can sometimes be hard to find the source. Cover your one ear and use a long hollow tube..Say like PVC plumbing pipe..As a makeshift stethoscope to help isolate it. Lots of things can squeal on these things and go away once they warm a bit. Last time mine did it was water pump but it has also been the bearings in the fan hub.