1997 GTP Very Loud Rattle at Idle

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?

I listened to various components with a metal tube (at my girlfriends who doesnt have any tools, so I had to use the metal handle from a swiffer). Anyways, when I placed the handle against the main drive belt tensioner, it sounds like there is a significant rattle coming from that. Is this a common problem with the Grand Prixs? Does anyone have any experience with the Dayco belt tensioners from Advance Auto Parts? I read one review that said that the replacement from Dayco for the Grand Prix is pretty crappy. Any thoughts? Thanks. Also, if you do think it is a tensioner problem, does anyone know how to tell whether it is just the pulley, or whether it is the whole assembly?

You can remove the belt and spin the pulley by hand. If it grinds or feels "brushy" then just replace the pulley.

If you pull on the belt while installed and the tensioner assembly doesn't puts "enough" resistance then it's bad. Some assemblies have a set of marks on them but I can't remember if GP's have them, hopefully other user can help.

Oscar.

Like oscar said, spin the pulley and see if the pulley bearings or theactual tensioner itself is your problem. If its the bearings, you may just be able to buy a new pulley. I think its left hand threads to get it off if my memory serves me correctly. Dayco replacements are good. Thats the brand we sell and I have yet to see a come back.

Tim is right, those are left hand threads, and I remember using a 15mm socket when I replaced mine for around 10 dlls.

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.

the bushings for the s/c snout ?

It still makes noise when the belt for the supercharger is removed, so its not the supercharger.

How many miles do you have on your GTP? This sounds like it could be a bad harmonic balancer. Over time the rubber inside the balancer will wear out and cause a loud noise when the engine is running.

It has 170000 miles. It does not make the noise when none of the belts are on, including the main serpentine belt, so i dont think it is the harmonic balancer.

WAIT!

If the noise is only present when the A/C is OFF, then check the air gap between the compressor and clutch, remove the serpentine belt and spin the compressor pulley by hand. If you see the gap is uneven as you spin the pulley then you can either rent a puller at most autoparts stores and reset the gap to 0.020" (I'm not sure about the correct value I'll look it up) or take it to a good A/C shop to get it done.

Oscar.

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? The gap you speak of is the gap between the clutch/hub assembly and the clutch rotor (which the pulley is around) right?

Have you tried just spinning the a/c compressor pulley by itself? Those bearings can make a lot of noise when they go bad..

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? The gap you speak of is the gap between the clutch/hub assembly and the clutch rotor (which the pulley is around) right?

I guess a bearing problem would be more like a humming sound, the air gap should be more like a rattling noise AFAIK.

Yes, the gap is between the pulley being rotated by the belt and the faceplate of the compressor (clutch).

Oscar.

Ok, so I finally got back to looking into this problem after I broke off a power steering bolt in the engine block and was dealing with that. Anyways, I adjusted the air gap on the A/C compressor and that did not stop the loud rattling I get at idle. So here is the latest: the car has a very loud rattling at idle, which disappears with just a small increase in RPM. Turning on the A/C at idle decreases the noise somewhat. I removed the supercharger belt: the noise DOES NOT go away. I removed the main drive belt and there is still somewhat of a rattle, although it is not as loud or as continuous. Could this be the crankshaft pulley/harmonic balancer assembly? I noticed when I had the engine dropped down that the rubber in the center of the the crank pulley was starting to deteriorate. Thanks everyone

I suggested that you check this earlier because the rubber will break down and cause the noise you are mentioning. (See post #9 of this thread.) If it does makes the noise with everything else disconnected then the only thing left is the harmonic balancer. Before removing it check to see if the bolt is tight otherwise replace it with a new one.

ok thank you. Any possibility it is the timing chain or chain tensioner? I hope not

Timing chain could be a possibility but it shouldn't make the noise you speak of even if it is going bad. If you would rather purchase a good used balancer for your car try moradpartscompany.com. Ed specializes in GM products and should have one available at a reasonable price or try the local wrecking yard.

OK, so I replaced the harmonic balancer and the rattling sound is now gone. However, I now have a squealing/chirping/whining sound coming from the belt area. It didn't do it before I put the new balancer on. The sound gets louder as the RPMs increase, and after the car runs for 10 to 15 minutes, it seems to almost go away. Any suggestions? It does seem to go away somewhat also when I spray WD40 around the power steering pump pulley (which is new). Just seems weird.

How old is the belt, as the belt may have stretched due to the bad balancer.

Definitely a possibility. Belt is at least a few years old I think. It would go away after the car got warmed up with a stretched belt? The belt tensioner is new if that helps

I put another belt on it that I had around (it is used) and now it doesn't chirp/squeal at idle but it does under power, and the sound doesn't go away after ten minute of running or so like it did with the belt that was on there. Also, there is a small coolant leak around my water pump. I believe it is the gasket, as it seems to be leaking out near the back of the pump over the power steering pump. The weep hole is under the pulley right, so I should get coolant on the belts and all around the engine bay if it was coming out of that right? (Just want to make sure my noise is not coming from the water pump, although I had the pump off a couple of weeks ago and all seemed ok).

If the coolant is getting on the belts then it will squeal. I know it is a pain but replace the gasket on the water pump and replace the belts with new ones and your issues should go away.

DUDE THANK YOU FOR POSTING THIS THREAD!!!!!

I was seriously about to dive into pulling the timing chain and replacing it.
I still might but the noise coming from the front engine mount (just like that ) tapping tap tap tap , taptaptap, rattle is alot better description.
then you rev it a little, and it dissapears,

mine increase while you turn off ac,
when AC is on and you are at a stop sign still rattles.
It has made me sick thinking it is metal failure of some sort.

i owe you dinner, and a milkshake!!!!!

now i have to fix the overheating issues ( i think it is the radiator )

Glad this helped you. I thought it might be the timing chain too at first and was ready to give up on my 170000 plus mile car. When I was searching for the problem originally, I broke off a bolt from the power steering pump in the block, which was a whole new evil. Anyways, again, glad it could help, but I owe a great deal of appreciation to the rest of those that posted to help me. I hope you get your overheating issues fixed. I have had those troubles too before, and have replaced just about every part of the cooling system over the years.

Wow!!
I entered this forum for the same reason, replaced all the parts mentioned here, I never thought of replacing the harmonic balancer, thanks everyone for your questions and responses, it seems like I found my answer before asking my question, wish me luck.