offshoreMM

Hi All. This is getting to the point where I'm going to scrap this car if I cannot locate the rattle. Well, not really, but I'm going to have to take it in and pay someone $200 an hour to track down the rattle. This thing rattles so noticeably that I probably wouldn't be able to sell the car as is, if I wanted to.

I have now replaced the exhaust tip clamps and tightened both exhaust tips to no avail whatsoever.

What has been done so far:

-Replaced cats with straight pipes, full stainless, new gaskets, new bolts, new nuts, new washers, less than 500 miles on them, all checked and re-checked and tightened.

-Replaced OEM mufflers with fabspeed mufflers. New gaskets, new bolts, new clamps. All tightened, checked and then rechecked. Less than 500 miles.

-Replaced OEM exhaust tips with high quality aftermarket tips, tightened, checked, and rechecked for rattles.

-Finally replaced the circular clamps that hold the lower pipes (tips etc) to the muffler output pipes. They were rusted. I was almost 100% sure that this is where the rattle was coming from because this was the ONLY remaining part of the OEM exhaust that hadn't been replaced (Yes, it even has new headers!). Made sure these new clamps were nice and tight today.

-Checked the clamps that hold the cats to the mounting bracket on the motor, tightened them. Started the car up and it still rattled, so I removed the clamps entirely (*temporarily) to eliminate them as a possibility. Still rattled even without clamps.

-Checked all exhaust piping to see if any rubbing contact was occurring. Nothing, all pipes etc are free and clear, and come nowhere near rubbing anything.

-Thought it might be a loose O2 sensor, tightened both just to be sure.

-Tapped the pipes with a rubber mallet, nothing.

I now have a 100% new full stainless exhaust system from the the headers to the tips. This is driving me nuts.

It sounds exactly how a loose exhaust clamp would sound if it were rattling around the pipping. It is definitely an external sound, it is not coming from inside of the motor itself. If it were any other car, the first thing I'd be checking would be a loose aluminum heat shield. It sounds like a thin aluminum shield is rattling somewhere, or an exhaust bracket. It's a 'clanging' sound, not the type of sound a solid piece of iron would make, nor is it the type of sound that the engine internals would make. I've worked on cars for years and years and this type of sound has only ever been produced by the above two problems (exhaust rattle, heat shield rattle). It is not coming from inside the upper engine bay area, it's coming from UNDER the car, in the outside engine/transmission area.

It ONLY makes the sound from 1,500 to 2500 rpms (when the engine is shaking a little more than usual). It sometimes makes the sound at idle for a short while, if I turn on the AC (again, engine shakes a little more than average when AC kicks on)The sound is loud enough to be heard over the catless full exhaust system. We live on the 14th floor of an apartment building, and my wife can hear me coming home from blocks away because the rattle sound reverberates off of all the buildings in our neighborhood and no doubt irritates people more than the exhaust, which I can actually keep relatively quiet at low RPMS.

Any further suggestions highly appreciated before I bite the bullet and take it to someone. I always cringe at the thought of bringing a heavily modified car into a dealer to get looked at, even though it's long past warranty. Roads are pretty poor here and my suspension is stiff. Is there any heat shield or other clamp somewhere that might come loose and make such a sound? At my wit's end with this stupid problem.

Sneaky Pete

Are you sure the 3 nuts that hold the muffler in place are tight? Are your motor mount nuts tight? Is a heat shield (the one that surrounds the muffler) rubbing on the muffler? Just a couple WAG's.

Doug Donsbach

Pull the bumper cover and make sure the heat shields aren't causing the problem.

TomF

Let us know what you find out. The heat shields have been suspect on my car for a while.

offshoreMM

Good suggestion on the heat shields. I've never seen them nor have I had the rear bumper off. As a last ditch effort, I'll put it up on a lift this weekend and have a friend rev it while I check the heat shields.

It feels like it is coming from the passenger side rear corner area.

Will also recheck the three nuts holding the muffler.


Whatever it is, it vibrates when the exhaust system vibrates.

Pac996

Haven't chased anythiny like that so I don't know if a 1/2x1/2" stick or dowl can get to most locations that might be jingling. But, with some good pressure on different locations I'd thing the sound would change when you are close the the source. There's also being able to hear noises down the length of a shaft like a dowl by putting your ear near the end. Doind so can let you know you are getting closer or further away.

Topaz330ci

Lately, I've been having a similar rattle at low rpm's and only once the car gets to normal operating temperature.

I have to start looking into it as I think it's slowly gettind louder.

TomF

I am experiencing the noise from the same area. The PO thought it was a heat shield, but I haven't pulled the bumper to check yet. Besides, if I keep the rpms above 2k, the noise doesn't occur!

lingpoen

Offshore? U find the c..k..er rattle yet? i just ordered mufflers-

offshoreMM

No dice yet. Going on the lift tomorrow. I suspect a heat shield. It's driving me nuts, and it's actually getting worse. What ever is rattling sounds like it's just about ready to fall off the car entirely. Whatever the cause, I'll be sure to post it here, because anyone else who ever develops this problem is going to go crazy trying to find the cause.

vange_c4s

hello everyone,

i too have been chasing this rattle. well i did my best to understand to figure it out this weekend.

symptom: passenger side rattle rear bottom, low speed related (1500-2700rpm)

after poking around for a bit, i was able to recreate the rattle by using the rubber coated end of a hammer being hit upon the exhaust between the cat and the muffler (the red arrow in the photo). i checked all brackets, mounts, an could not effect the rattle. as best i could tell, the noise was from inside the muffler (green arrow). i could hear it out the exhaust tip too. so i have heard about baffles in the muffler breaking free and making noise. does anyone else have experience with this?

offshoreMM

I solved my rattle problem after putting the car on the lift.

It was coming from two places:

1. Passenger side heat shield between muffler and engine was slightly loose. A 1/2 turn with a wrench tightened that right up.

2. One of my O2 sensor simulators was loose on one of the straight pipes. I checked it before with my hand and it wasn't rattling, but with the engine warmed up it started to rattle. A quick turn of the wrench and it was re-seated properly again and I can now drive my car in peace!

offshoreMM

@ vange_c4s : Are you sure it's not the rusted C-clamp that is holding your tip to the muffler out-pipe? Mine were completely rusted like yours, and I'm surprised they weren't rattling.

pecto3

Hey Vange, I picked up my 2000 C2 sometime ago for a very cheap price, rattle was prominent when driving, PO did not bother to pursue it, probably due to known IMS issue. After I did my own inspection, turns out it was the passenger side muffler. Change muffler but similar sounding rattle persist. Did the tapping test using rubber mallet on both cats, driver side cat was toast. All in all, $600 for cat and muffler from a dismantler. Hope yours is as simple as that.

vange_c4s

offshoremm,

i checked heatshields - dont think its that. i pulled on the post cat o2 sensor and no change in sound. and the c clamp, well thats tight too.

pecto3,

it does not make noise from the cat - i think. sounds like passenger side, though i have been fooled before chasing noises.

thanks for your inputs