A/C Compressor knocking

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solracmopar

solracmopar

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I just installed a new a/c compressor on my 318. I'm getting a knocking sound whenever the compressor is on. It doesn't happen when its off. Anyone have any idea? Thanks
 
Oil? Compressors have rods and pistons just like engines
 
If you're sure it isn't just running noise, some of those sanden units make a rattling pump noise when they are running, I'd pull it and take it back.

Usually new and rebuilt pumps come with oil in them, or tell you how much oil to add. As mentioned already make sure you have done/verified this.

Was the original pump destroyed? Could there be metal in the system? If so, did you flush the system?
 
Just a note I would like to add is, that sometimes the belt slipping when the compressor pump is under a load sounds like a knock.
Try tightening the belt a little and see if it goes away.
 
Thanks for the quick response guys. The car is at a shop and they did the entire install. The original compressor was shot so I went to advanced and got a stock replacement (2 piston I believe). They completely flushed the system, new condenser, new dryer, new control unit and new under dash vent set up.

When I took the car for a test drive today the a/c blew ice cold. Only downside was that knocking sound. They said it could be cause the compressors so new. Could be a case where it needs to break in? I honestly have no idea. I've never had an a/c work on either of my A bodies.

I later found out about the newer style sanded units. Wish I had known before to having the shop do all the new lines for the older style compressor.

Heck maybe its a bad core?
 
Stock would be an RV-2 compressor, a heavy beast but rugged and reliable. Simplest would be to first try changing the clutch, but most likely it is a bad rebuild and returning the whole thing might be the only way to deal with Advance on it. Get your shop to evaluate and give you a write-up on the problem to take with it.
 
solracmopar said:
I just installed a new a/c compressor on my 318. I'm getting a knocking sound whenever the compressor is on. It doesn't happen when its off. Anyone have any idea? Thanks
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Hi,

It's hard to tell if your new compressor has a problem with out actually hearing it. RV- 2's are noisier than newer compressors. They make their own unique sounds when moving refrigerant around.

As far as I know only rebuilt RV-2's are available these days and most of the chain store rebuilts are Four Season units. Four Seasons are not known for the best rebuilt compressors so you may indeed have a bad one. I'm not sure were you can find a quality rebuilt RV-2 these days.

Also, the installer is responsible for insuring the right quantity and type of oil is used. These compressors were originally used with R-12 refrigerant which used 525 A/C mineral oil. Today's more common R-134A would use PAG or Ester oil. Since the rebuilder has no idea which refrigerant will be used They often ship the compressors dry or with some type of shipping oil which must be drained out and the proper oil put in.

Belt tension is critical or the belts slap around and make strange noises. I've never heard of a break in period for these compressors.
 
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This is all solid feedback. I called the shop and explained all the info you guys offered up. They are going to take the compressor off and swap it out with another one from Advanced. All in hopes that it fixes the issue.
 
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