Rattle noise from A/C compressor

Thanks to a post in a sister forum, I think I found the source of the noise from my A/C compressor.

I had recently replaced the compressor, accumulator, orifice tube and hose manifold on my '84 Silverado due to a severe rattling noise from the compressor area. I had also thoroughly flushed the remaining hard line, evaporator and condenser finding no signs of "black death" or any type of debris in the liquid that was flushed from system. Triumphantly, I took the vehicle to the local repair shop to have them vacuum the system down, and install the R134A they had evacuated from the system prior to my DIY repair. When the system was checked and filled, I had ice cold air with no noise!!!

To my dismay, the rattling noises I experienced prior to the repairs was back within a week. System was still blowing ice cold, and the noise was only apparent at idle, if RPM's were increased, even slightly, the noise went away.

I started searching this forum, Youtube, Google, and everywhere I could think. Then I found it, a post on the Corvette forum describing the exact issue, and explaining what they had found. Simply loose and missing hardware from the compressor, allowing the compressor to become loose after a short time, resulting in the rattle. When I examined my system, I found a missing washer from the one mounting point and actually a missing nut from one mounting bracket, (see photos below).

I then realized that the initial noise to the first compressor only started after a mobile "technician" had removed the compressor to gain access to the valve cover on the drivers side to replace the gasket. I had been very careful when I replaced the compressor to make sure everything went back the way it was found, not knowing that the previous "technician" had failed to do the same.

With a quick trip to Ace hardware, I got the missing parts, returned home and installed them, then nervously hit the key, and, shazam!! no more noise.

The fact that I had just spent several hundred dollars in parts, plus my time to replace components that were probably not needed was bad enough, but what really frosted me was that I had taken the vehicle to 2 different shops to have the noise diagnosed, and they both said it needed a compressor, and of course all the other parts of the system because they were obviously contaminated, repairs would total well over $1,000.00!!

My points on this post are two fold, 1st, the obvious fix is not always the correct fix, and 2nd, as most of us already know, there are a bunch of "technicians" out there that while maybe not being criminal in intent, don't do the proper diagnosis before starting to run up the bill by throwing parts at a problem.

Hmmm...I need to take a look at mine, I am using a truck compressor with a car bracket though. I've got a rattle something fierce, figured it was the clutch but it might just be that.

The funny part of this is, Corvettes have passenger's side compressor mounting! I knew about the hardware issue with R4s with driver's side mounts. The spacers/washers look a bit cobbled up, so I can see how it happened. Never thought about it with the Corvette mount.

Intermittent problems are the worst. Were you able to duplicate the noise in the technicians presence. The person installing the new compressor should have at least noticed the missing hardware. Sadly most technicians these days are just parts changers, sorry.

I was the person that installed the new compressor, and was very meticulous about putting everything back where it was, had no idea there was a missing washer. I'm afraid you are correct, about technicians being parts changers, especially on an older model vehicle. If they can't plug in the computer to tell them what's wrong, they don't have a clue.

Similar problem on my 86. I thought it was a compressor or more serious issue. After reading this post, I inspected for missing parts, loosened all PS and AC related belt tension bolts, then tensioned belts and torqued bolts. Rattle is gone (so far). Posted notes and photos because the 86 is a little different. All praise to the saints of gmsquarebody! An easy fix. Thanks.

While I agree some techs today are parts changers, think your being a little over critical. If the bolt was missing, can see where you have a point but the washer? Assembly manuals aren't something a tech today looks at or even has available, especially on a 40-year-old vehicle. Mounting systems are much better today, not a common problem.