AC Squeal - Any ideas?

Hey, I have a 2000 XJ 4door 4.0L Auto Cherokee.

I have had an issue with my XJ where when I initially start the jeep after it has sat for a while (usually consistent after one day of sitting), it sounds like a serp belt is squealing. This only happens when the AC is on and it goes away after a few minutes. It doesn't gradually decrease in volume, it just stops all of a sudden. It also gets worse when I drive and the Revs increase.

I changed the serp belt which was a bit worn, tightened the belt properly, and installed a new AC clutch. Nothing has changed. I'm wondering if it's a pulley, but I haven't been able to find anyone who has had the same problem.

Any ideas?

Thanks in advance.

The XJ Cherokee requires the belt be very tight. You can buy a krikit belt tension gauge, or just add 1/4 turn of tightness every time it squeals.

Tim_MN said:

The XJ Cherokee requires the belt be very tight. You can buy a krikit belt tension gauge, or just add 1/4 turn of tightness every time it squeals.

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I agree.
My experience with my '00 is that the "yeah that looks about right" method does not work.
I use the Krikit II.
180 to 200 lbs for a new belt.
140 to 160 lbs for one that has been on awhile.
I always use the numbers at the lower end of those ranges when I do mine.

I'm not sure if all a/c pumps are the same, but I've been told that the freon actually lubricates the pump? It could also help to make sure the system is fully charged.

Normal occurrence, the alternator goes high output causing the slip along with the increased load from the compressor.

Just keep tightnening a little at a time until it goes away...these belts need to be VERY tight. (and good quality)

jrmyers said:

I'm not sure if all a/c pumps are the same, but I've been told that the freon actually lubricates the pump? It could also help to make sure the system is fully charged.

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A/C compressors use a PAG synthetic oil for lubrication.
https://refrigeranthq.com/f-a-q/what-is-pag-oil/

dktool said:

Normal occurrence, the alternator goes high output causing the slip along with the increased load from the compressor.

Just keep tightnening a little at a time until it goes away...these belts need to be VERY tight. (and good quality)

Click to expand...

Immediately after starting the alternator is under load to recharge the battery from the start. Adding the a/c compressor is about the biggest load the belt will see.


So tighten the belt some more. It doesn't feel real good to tighten things a lot because the excess tension may help the water pump bearings to fail. Just tighten until the belt doesn't slip any more. (or use the tension gage)



HOWEVER! On my '84 I encountered the situation where the installation of a new belt saw slippage no matter how tight I cranked things down. In that case it was that the alternator pulley grooves had worn so badly that the W shaped belt grooves of the new belt wouldn't adequately engage with the worn pointy grooves on the alternator pulley. New pulley solved the problem.

I had a similar issue with my 99. My old belt was squealing often and tightening it didn't seem to make any difference. I read some threads here about this problem and the suggestion was to buy a Continental belt (#4060950, the old Goodyear Gatorback belt) and avoid the generic parts store belts.



Afterward, I had to re-tension the new belt a couple of times before I got rid of all of the squeals - when people here say "tight" they mean TIGHT - the thumb method to gauge the tightness of the belt just doesn't work on the XJ with the manual tensioner.



In your case I'd say try cranking the tension tighter on your belt, or if the old belt has some miles on it maybe replace it with a Continental belt.



I bought a Kricket belt tension gauge but discovered that there isn't much room to use it.

EvaB99XJ said:

I bought a Kricket belt tension gauge but discovered that there isn't much room to use it.

Click to expand...

You are right. It is a little tough to use.
And I prefer a longer distance between pulleys to use it on.
But still has to be better then the "yeah that looks about right" method.

Would a belt dressing be a good idea? Something that would
add a bit of friction to the belt and pulleys?

That A/C squeal has always irritated me.

Belt dressing bad on serp belt.

http://www.daycoproducts.com/why-belt-dressing-is-not-a-solution-to-quiet-a-noisy-belt

Thanks for that link, Saudade.
I didn't realize belt dressing was so harmful.