C3 - Belt Noise or Squeal

[Lee S.]

I've had a long term project going to get the AC operational on my 1974 Coupe w/454, Auto, PS, PB, AC, and complete A.I.R. System. I've installed a Delco rebuilt compressor. With a full load of fresh R12, I now have very cold AC, and a new problem.

With the AC on, there is very loud belt squeal at higher RPM's, i.e., momentarily goose the accelerator to about 3000 RPM, kick-down acceleration while driving.

All of the belts are new (Quanta) and tension is as tight as it can go on each belt.

I have squirted the belts with the usual auto parts sprays.

Any help would be appreciated.

Lee Snyder

[Don G.]

Re: C3 - Belt Noise or Squeal

My advice would be to first remove the belt that drives the A/C compressor. If the noise goes away, you have isolated the source to some extent. I had this problem with my wife's '75. I replaced the bearing behind the pulley and the noise went away. The service manual tells you how to do it without cutting in to the freon system.

[Lee S.]

Re: C3 - Belt Noise or Squeal

Don

I think I met you at the Michigan Chapter meet at Meadowbrook. I have the 1974 Medium Red Big Block Coupe with Silver Leather. I remember discussing the roadsters you have.

The noise is only present with AC on and was not present prior to replacing the compressor. I guess it is possible but what are the odds of a bad bearing on the rebuilt compressor?

I think I'll take another look with the stethescope tomorrow. I'll look at my Chassis Service Manual also. Any special tools required?

Thanks

Lee

[John H.]

Re: C3 - Belt Noise or Squeal

Lee -

Did the noise arrive after you installed the Quanta reproduction belt? Before tearing into the compressor, I'd try a good current-technology belt on it - like a Gates "Top Cog" or Goodyear "Gatorback".

[Lee S.]

Re: C3 - Belt Noise or Squeal

The Quanta belts and the new compressor went on at the same time. I only replaced the belts in anticipation of Flight judging. Prior to the belts, I had no noise... I also had no AC! So it is hard to see what came first, the chicken or the egg!

I still have the belt I removed which is a Gates belt and is a cog design. I'll reinstall that and see what happens. This is an easy belt to do. Power Steering on the other hand is a royal P.I.A.

Regarding the Hi Blower port at CRPL from about 2 weeks ago (spent a weeks vacation in Hilton Head to recover from the power failure), it was the blower speed switch. Your advice really helped diagnose this. Wiring colors and configuration were the same as you noted from the 1972. When I get back to work I'll close out that thread on CRPL in case someone else runs into a similiar problem. You know, I'd rather replace ball joints instead of working inside that console. Another P.I.A.

[Lee S.]

Re: C3 - Belt Noise or Squeal

Changed the AC belt to the Gates cog type belt and verified the others were tight... no difference. Squeal starts at 3000 RPM (only with AC on). I had my son sit in the car and hold the gas pedal at 3000 - 3500 RPM while I probed and listened with a 24" piece of heater hose. I could not pin point the noise. I then had him toggle the AC off and on. Sounds from the AC comperssor, A.I.R. pump, and alternator do not seem to change. As you can imagine, there is a lot of engine noise... induction, exhaust, and fan rush at 3500 RPM with the car sitting still. It may be from the AC comperssor clutch area?

One thing I did notice, is a momentary change in RPM on the the clutch fan as the AC was toggeled off and on. While I would expect this because of the increased load, it is at this exact moment when the squeal starts. Can a fan clutch make this noise?