I have an interesting rattle noise on my disco. I think I've tracked it down to the a/c compressor. I did this by using my breaker bar as a stethoscope. It's a rattling noise that I can only hear at idle. I think it gets drowned out by engine noise as the RPMs go up. I took the serpentine belt off and the a/c pulley has a little play in it. The compressor clutch appears to be working as it should. It engages when the a/c is on and disengages when off. I took this video of the noise. Any thoughts on what this is?

 

Sound like an exhaust rattle to me.

 

Check the idler pulley below the A/C compressor I had a similar noise and that's what was doing it in my case. It got louder when the clutch kicked in so I thought it was the A/C pulley. D*

 

LR03NJ, That's what I thought at first too. But the noise is all top end by the a/c compressor. My "stethoscoping" didn't give any rattles from the exhaust system.

d.a.r.y.l That might be the case. That pulley definitely wasn't as smooth as the other idler pulley. Probably couldn't hurt to replace it.

 

Both idler pulleys have bearings held in by a snap ring.
Neither of mine make noise, but one doesn't feel as smooth as it should.
I will replace them eventually. I've yet to try and find replacements by size or number, but I'm sure you could buy 20 of them somewhere, vs the cost of one from LR.

 

Since you already have the shroud off, I’d loosen the belt, remove the pulley (soak the bearing) in some WD40 or good lube, clean it off well, re-install it, and see if the noise is still there. Then you’d know 100% it was the pulley bearing.

 

Hopefully its the pulley. I just wonder why the sound is not consistent with the rpm. Sometimes it sounded more and sometimes less. If its a pulley, it could be the tensioner spring but its far from the compressor. I thought it was the catalytic converter at first or a heat shield that got loose. Anyway, good luck.

 

Had the Disco in the shop and asked the guys to have a look. They also concluded that the noise is coming from the a/c compressor. The solution they offered was to keep an eye out for good used compressor and not to worry too much in the mean time.

 

Disconnect the belt totally and run the engine for max of 60 seconds. If the noise disappears it's one of the ancillary pieces of equipment, alternator, idler, or the A/C compressor otherwise it's coming from elsewhere.

PS: IMHO it sounds like the crankshaft pulley delaminating which is a PITA to fit and torque. Don't forget to change the oil seal and bolt + washer.

 

Sounds like the shop has at least one idiot working there.

If there's play replace the A/C pulley bearing before it fails. No need to swap compressors and pay to have it serviced.

When you have the belt off again check each pulley and idler for play and/or dragging bearing by rotating by hand.
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