R4 A/C compressor very noisy at idle?

[Rock_Hudstone]

Well, I swapped in a known good R4 a/c compressor in my 1987 Olds Cutlass 442 to replace a working, but noisy compressor thinking that compressor was going bad.

Unfortunately, the replacement compressor is noisy as well but only at idle, just like the other. Sounds like a loud metallic rattling/buzz. Off idle and at speed the noise goes away and everything is fine.

Pressures are 25 psi low side, 175-180 psi high, vents are blowing cold even with only 30oz. of the required 3.25lbs refrigerant.

Any ideas, low oil perhaps?

 

[Chris142]

those r4's have 4 pistons and a thin housing. they all rattle

 

[Rock_Hudstone]

Originally Posted By: Chris142
those r4's have 4 pistons and a thin housing. they all rattle

Yeah I know, they all have a slight buzz to them, but this one is off the charts noisy, but again only at idle.

 

[Propflux01]

Since you had the system open at least once, did you put the proper oil and amount during last recharge?

 

[Rock_Hudstone]

Originally Posted By: Tim H.
Since you had the system open at least once, did you put the proper oil and amount during last recharge?

Yes, I drained and measured the oil from the old compressor and added the same amount to the new one.

 

[Rock_Hudstone]

Okay, problem solved. Took it to my master mechanic that I used when I'm stumped.

He listened to the noise and immediately said it was the belt. I said no way does a belt make a noise like that. I then explained my unlikely, but plausible theory of low oil, blah, blah, blah.

He got out his mechanic stethoscope, put it on the compressor and said again the belt wasn't tight enough. I still didn't believe it so we tightened the belt up and the noise disappeared.

Not the first time he has been right on the money either.

 

[The_Eric]

Yep, belts can make some odd sounding noises when too loose. We just had one the other day making some rattling noises at and just off idle. Turns out the tensioner pivot was seized. The belt had been replaced a while ago, but nothing else. A new tensioner and idler and all was well.