Hello,
98 XJ 4.0
I have been having intermittent whining or squealing noises coming from one of the pulleys on the serpentine belt when idling. I'm pretty sure the noise is coming from the AC Compressor pulley.

The noise started happening in the morning when it was colder and wet outside. It was occasional and would go away relatively quickly and it would never make the sound when the engine was warmed up. It has become more frequent lately and lasts longer before it goes away. The pitch changes with RPM's but goes away/less noticeable when driving.

I took it too a shop a week ago and they diagnosed the problem as my serpentine belt being too loose. I just replaced the belt and idler pulley three weeks ago. They tightened up the belt but it still makes the same noise. I tightened it up even more a few days later but still didn't help.

I have been researching and I believe the noise to be either my AC Compressor bearing or clutch. I posted a video on youtube and was hoping someone would recognize the noise as either of the two.


Any suggestions of how to diagnose either of the two problems once I dig into the project this weekend?

Thanks for you help.

 

Sounds like the compressior is going out to me

 

Doesn't sound like a loose belt. Loose belt has a much higher pitched squeal.

 

I noticed in the video that your a/c was not on. When you turn it on does the whine increase, stay the same or otherwise? That doesn't sound like a belt squeal at all to me.

 

When I turn on the AC there is a different noise, more of a "screaming." This was the first noise I noticed related to the issue. It first occurred when it was hot outside, and when I would turn on the AC with a full load in the Jeep, it would "scream" when I hit the gas. If I turned the AC off, the noise would go away. I haven't been using the AC much recently; but tomorrow morning I'll turn it on while the original noise is going on and see if I can get another video. Thanks.

 

Since that is the case I'm thinking your compressor is shot. The bearings are causing that noise and it just gets worse under load when the compressor is under load. I'm betting you replace it and noise goes away.

 

To avoid buying a pricy new/rebuilt compressor get a new bearing it's about 30-40 dollars.The bearing is a press fit in the pully(so you have to beat out the old one), make sure you get the right bearing. DON'T lose the small shim washers. The best way I found to get the new bearing in is to put the pully in a gas grill on low, and the bearing in a baggy and into the freezer(if you can mix up some rock salt and put it in that it works real well). heat and cool everything for about 15-20 min, make sure you get it on the first try when you drop the bearing into the pully or you'll have to start over. Once you get it right drop the the hot pully into some warm or hot water and let cool. If you have access to a press then you don't have to go through all of this.

 

Thanks for the advice... did you have to use a pulley puller to get the clutch/pulley off the compressor? Any special tools? Did you have to remove the radiator?

I found this bearing from another thread that I believe is the right one. My compressor is stamped "709D" on top and the tag says model number: U 4691
http://www.ackits.com/merchant.mvc?S...&Category_Code

I'm considering trying the bearing first before just replacing the whole compressor but I'm not really sure how difficult getting the pulley off will be.

 

So I take back my previous statement that there is a second noise when I turn on my AC. The shop said they heard the noise when they turned on my AC, but I haven't heard the noise with AC on since the summer. The sound was higher pitched than the current sound and I think was a loose belt. Here is a video from this morning when it's making the noise and I turn on the AC... didn't really change the noise much.


I'm hoping I just need a new bearing... Any insight would be appreciated.

 

Doesn't look like the clutch stays engaged. It should spin more than a brief second. Replacing the bearings might work but I've never attempted on one of these. I'd replace the whole thing but if it can be fixed on the cheap I'd give it a shot.

 

From what I can remember the clutch has always stayed on for a few seconds, turned off, then turned back on for a short period of time, and repeats. I thought that was normal and it's done this since I've had the Jeep. AC works fine, haven't had trouble getting cold air.

 

I've been doing a/c work for almost 15 years and have never heard that pitch of noise before.

I don't agree with just replacing the bearing. Compressors aren't very expensive. You can get a Sanden from Rockauto.com for about $160. Why not replace the entire compressor? It's almost 15 years old. The reed valves in it are probably worn. It does appear to be short cycling to an extent, so I'm sure it's low on refrigerant. Replace the compressor and accumulator/drier. Then take it to a shop and ask them to pull a vacuum on it and charge it with the correct amount of refrigerant.

Oh and get a stethoscope and pinpoint it is the compressor. It could very well be an idler pulley or tensioner.

 

I agree on making sure the compressor is the suspect making the noise. You can also use a rubber hose with one end held to you ear and move the other end around to pin point where the noise is coming from if you don't have access to a stethoscope.
I someone that's been doing a/c work for 15 years I'd take their advice and just replace the whole thing if it is determined to be worn out.

 

pulling off the pully is just a straight pull be patient you can work it a little with the help of a small pry bar, and be aware that the clutch magnet is behind the pully. Also be careful with pulling off the clutch disc do not bend it.
As far as pump replacement it is up to you as whether to do the whole pump or just the pully. A vac test before you spend any more than you have to should be done first some shops will do it for free if you come back to them for refill, or if you let them have what refridgirant they took out. The factory compressor on my 90 was changed in 08 for the first time due to a blown front seal, and I have noticed that jeep compressors last a little longer than others. But when in doubt change the whole thing.

 

I just replaced the idler pulley so I know it's not that. The sound is definitely coming from the passenger side of the engine bay. There are only 3 pulleys that are on that side-- the AC compressor the fan clutch and alternator. I'm almost positive it's the compressor but I'll check before I buy any parts