2002 C2 Exhaust-like Rattle, Cannot Locate, Extremely Frustrating

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.

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.

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

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

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.

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.

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.

Quotes source post: 9707713

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!

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

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.

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?

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!

@ 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.

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.

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

vange_c4s: You need to get a friend to help you. If you can reproduce the sound by sitting there and blipping the throttle, as I could, you can get a friend to get behind it and try to localize the source of the sound. Just make sure they don't put their head near the exhaust pipe =) Possible sources: Tip, tip clamp, head shield between muffler and engine, heat shield on bumper side might be rubbing a muffler, your clamps are all rusted -could be one of those, check the flanges and make sure they aren't loose -when I first bought my car, one bolt was loose between the header and cat pipes, this caused the gasket to blow out and rattle. Get in the car, blip the throttle, and have a friend stand off the rear to the side and press their foot up against the (top of ) the tip and see if that quiets the rattle as you blip the throttle. If so, then you have a rattle coming from between the muffler and tip. Since you are in Mass., you might have more rust issues, especially with the shield mounted between the muffler and engine. It is held on by two screws. You can see it from under the car, or with the rear wheel off looking directly towards the motor from the wheel arch. I've seen those rust to the point where they are falling apart on cars that have been in coastal areas or places that rain a lot. The last thing I'd check is probably the three bolts holding the muffler to the muffler bracket on that side. Hard to reach, but you can manage if you jack the car up and have flexible arms and a flash light. My car has only two O2 sensors, so the other two holes on my bypass pipes are plugged with threaded plugs and washers. Even these came loose after about 2500 miles due to poor roads and a stiff suspension probably. Check all 4 O2 sensors with a wrench and see if there is any play in any of them. They might seem tight when the engine is cold, and you check with your hands, but once the pipes start heating up, they might rattle if even slightly loose. You can also try blipping the throttle and having a friend reach up under the side of the rear bumper and grip the heat shield against the bumper, and see if that eliminates the rattle. That would narrow it down to a heat shield rattling against the muffler on that side. My O2 sensors were hand tight at least when I checked them. Not until I got a wrench around them did I realize that one was actually pretty loose. Worth rechecking with a wrench.

somethin might came loose with the clamps

I am having an annoying rattle issue, I have a 2001 tiptronic turbo, when slowly accelerating there is a loud rattle coming from the rear passenger door area and there is an RPM pulse/surge until getting to 2000 RPM when the noise goes away. This was only happening when the car was cold and went away when it got to temperature, but now it seems to be a little more consistent/persistent. It sounds like a metallic rattle, I have not been able to track it down. Anyone have anything similar?

I know the plumbing and shielding is different for a turbo, but I assume the same basics still apply: the metallic rattling is typically one of these things: * A loose heat shield; * A chunked catalytic converter element; * A loose internal muffler component; * A loose clamp or other connector; * A hard line, hose, or other object has come loose and is now resting against an exhaust component. On non-turbo cars, getting it up on ramps and judiciously applying a rubber mallet is my preferred way of identifying the rattly component; given the additional piping and turbo equipment, I'd be even MORE judicious.

would these account for the surge in RPMs when it happens and why only at 1500 rpm?