Thread: Guess this noise.

2000 Pontiac Grand Prix GTP - Mystery Howling/Whistling Noise - YouTube


Anybody know what is making this noise? It's not the Supercharger or a pulley.

Being it's intermittent, it's a rarity it keeps doing it at idle long enough to chase anything down, I have already switched AC on and off while I was driving when it was doing it with no change. Since I have a ton of spare parts, I went and switched out PCV to see if it will go away. We shall see, the old one did seem free when shaken, but doesn't mean it wasn't sticking.

Well swapping the PCV had no effect. Still does it intermittently. Seems a little more prevalent when first starting to drive when cold, but really unable to distinguish any real pattern or isolate the offending part.

Any other ideas?

Originally Posted by Scottydoggs

didnt say to swap it, said to open the oil cap and see if it goes away. put your hand over the hole and feel for suction. under the pcv could be clogged up, or another passageway.

we hear this same sound after intercoolers are installed wrong and block a pcv hole up.

Got it. I understand what you're saying. Biggest problem I'm having right now is its not continuous long enough for me to chase down.

If it sounds just like that video, mine did that exact same thing intermittently only at idle forever before the alternator ate itself. Took the belt off and you could barely turn it.

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I did check all the pulleys prior to this post. Only one seemed suspect and I changed it.

I did have a chance to chase it down for a little bit at idle and it really sounded like it was at the Supercharger inlet because I could hear it the loudest at the Air Filter. It's either that or the side cover of the Transmission.

Ok, this thing has me chasing my Tail. I'm thinking it may be the AC Clutch/front plate. Haven't been able to confirm yet because it's still intermittent. There is no change if I take the Oil Cap off when it's doing it and also no change if I turn the AC on while it's doing it. So that's a little suspect.

Have you been able to use a mechanics stethoscope or something similar to try and narrow it down? I don't know where at in STL you are, but I have a mech. stethoscope in the garage that I use for this kind of stuff. I'd be more than happy to swing by and help out. I'm not overly familiar with the M90 cars but may be able to lend a hand. I HATE intermittent issues. I'd rather have the damn thing fail outright than just make a noise every now and then.

Originally Posted by FordMan77

Have you been able to use a mechanics stethoscope or something similar to try and narrow it down? I don't know where at in STL you are, but I have a mech. stethoscope in the garage that I use for this kind of stuff. I'd be more than happy to swing by and help out. I'm not overly familiar with the M90 cars but may be able to lend a hand. I HATE intermittent issues. I'd rather have the damn thing fail outright than just make a noise every now and then.

No I don't have a stethoscope. I appreciate the offer, very nice. Thank you, but if be afraid of wasting your time if we could not get it to make the noise while you were helping. I went ahead and ordered a new AC Compressor. Couldn't pass up the deal for a new Delphi for $100.00. The current one has been on the car for close to 400K. Pretty sure it's the clutch/ bearings making the noise. Hope I'm right, but if not at least I'll know that part is new.

Well if you change your mind let me know. No sense beating your head against it. After 411K on my GP I've heard some really strange noises, lol. Some not so good but always fixable.

Thanks for the help everyone. My guess ended up being right. My new AC Compressor arrived today an not a moment too soon. After driving home from work, went to try and start the car again to see if it would make the noise and the motor wouldn't even turn over. The AC Compressor clutch was pretty much locking up. Swapped out the Compressor and won't try to charge until I can get the AC Recharge kit here and pull a vacuum on the system.

Good deal! Question is was it the clutch or the compressor that locked up? The only reason I ask is if it was the compressor then you could have metal junk in the lines which would require a teardown of the A/C system to clean out the lines.

Don't forget to replace the accumulator while you're at it. Might want to consider the orifice tube also. Went through this last year with my GP and it was completely covered in junk to the point it wouldn't cool anymore. Bad thing is the tube is located in the line under the brake booster and is a PITA to get out.