Under Hood Screech at High RPM

[Bill Lloyd]

I have a base engine '72, 350, 200hp,Engine CKW. The car has PS and AC. If I accelerate sharply, the engine make a screech as the RPM increase. I first thought that this was a belt noise. No dice. Belts are new and properly tensioned. Could this noise be the clutch fan? The noise disappears as RPMs level off. Everything else under the hood seems ok. Comments?

Bill

[Wayne C.]

Re: Under Hood Screech at High RPM

I'm not sure "new and properly tensioned" belts means much, if something's dragging it still can cause belt squeal. Sounds like maybe the A/C pump/clutch. See if you can replicate the noise with the car sitting still in neutral, then you could look and listen with the hood up while someone else revs the engine sharply.

[Michael W.]

Re: Under Hood Screech at High RPM

Assuming there's not somebody's cat missing, I've been told that an overcharged AC system will cause excessive load on the compressor and may result in belt squeal.

[Don G.]

Re: Under Hood Screech at High RPM

I had a similar problem with a '75 L48 auto with air. It would make that same noise on cold start and disappear within a minute. I removed one belt at a time and determined it was the ac compressor. I replaced the bearing and it was fine. The bearing can be replaced without cutting into the freon system.

[Patrick H.]

Re: Under Hood Screech at High RPM

Bill,

While they've all mentioned the AC, don't forget that the alternator belt gets REALLY close to the PS pump, and can rub on it and give you this EXACT prblem (don't ask how I know ). That's why teh PS pump even has a little belt rub guard on it. I found that the new PS belt I had was just a touch too short. This allowed the PS pump to interfere with the alternator belt only above, say, 3000-3500 rpm, or when under brisk acceleration.

It's a lot easier to remove the PS belt and adjust it out of the way to see if this stops the noise than to fix your AC.

Patrick