Loud rattling noise coming from belt area

I have a 97 GTP. When I am at idle, I get a very loud rattling noise coming from the drive belt area of the engine. The noise goes away when you rev the engine up, but returns immediately when idling. I removed the supercharger belt assembly, and then noise still occurs. This just started tonight out of the blue, and It is extremely loud. Anyone have any suggestions?

Sounds like it could be your timing chain.

Sounds like your Supercharger Coupler.

I removed the supercharger drive belt and the noise is still present when the supercharger is not turning. Also, the coupler is less than 6 months old. Also forgot to mention that the noise lowers somewhat when I turn the A/C on. Could it be the tensioner assembly? How would I check this? Thanks for everyone's help

It's your a/c compressor. The one I just got does the same thing... I was told it's a buildup of some kind between the pulley and the thing that's fixed in place on the end of it. Not sure how to fix it yet. It goes away when the compressor turns on because the clutch engages, spinning the whole thing.

I don't think its the A/C. Noise is not coming from that area. I listed to various components with a metal tube (at my girlfriend's who has no tools, so I had to use the metal handle of a swiffer). Anyways, when I placed the handle on the main drive belt tensioner assembly, it sounded like a very significant rattle coming from that. Is this a common problem with the Grand Prixs? Also, does anyone have experience with the Dayco tensioner assemblies from Advance Auto Parts? I read one review that said these were pretty crappy. Anyone else have any thoughts? Also, does anyone know how I could tell whether it is just the tensioner pulley or the entire assembly itself, if you indeed think these are my problem to begin with?

I replaced the whole tensioner assembly. That did not fix it. I removed the water pump and checked it. That doesn't appear to be the problem. However, I broke off one of the power steering bolts in the block in the process, and I am trying to get that taken care of. What a PIA. I will have to take it to someone to get that fixed. The rattle still isnt fixed though. However, it does mostly go away when the A/C is turned on.

Then it's the ac compressor clutch. sometimes it's spacing, sometimes it's the bearings.

Is there a way to confirm for sure its the A/C compressor? Would I have to replace the whole compressor because those are expensive?

Pick up a mechanics stethescope. I find mine invaluable for listening and confirming which pulley or accessory is causing problems.

I tried to listen with a long metal breaker bar. It sounds like its rattling everywhere: tensioner assembly, water pump, A/C. I am not able to distinguish where.

Well a screwdriver can work, but it's not as precise as a stethescope. Which is why I suggested the surgeon type tool versus the farmer tool.

Have you tried removing the acc. drive belt and spinning all the pulleys by hand? This is how I found the A/C compressor on my 95 Bonne to have bad bearings. It was making all kinds of nice rocks in a metal can noises, but still worked. And yes, the sound got less with the A/C on.

I have spun the pulleys, and I do get a little noise from the A/C compressor, but nothing even remotely close to the sounds when it is running at idle. The alternator also has somewhat of a brush like sound when spun by hand. If it is the A/C compressor, is there anyway around having to replace the compressor and recharge the system again?

Like I said before... it's your A/C compressor. It doesn't always mean something is wrong with it. Also there's no way you'll be able to spin it by hand as fast as it turns while the car is on.

small sounds when you spin them slow are excessively louder and more violent when spinning fast.

I had the alternator run on a tester at Advance Auto. It didn't make any noise whatsoever. I guess that leaves me with the A/C compressor. Is there a way to distinguish between a problem with the air gap between the clutch hub assembly and the clutch rotor and a problem with a bearing?

Bearings will sound like a whining noise at speed. Similar to your supercharger if you're lugging the motor up a hill in a high gear.

The other sound is benign, so I've been told.

prob your s/c coupler

A/C compressor doesn't whine when up to speed. Only that loud rattle at idle (which I am assuming now is the compressor). Its not the S/C coupler, as the rattle does still occur with the supercharger belt off.