I have this strange sound from back area of car but only under a specific condition - sort of a higher pitched buzzing/rattle metallic noise - Its quite loud when it occurs and coming from the back end.

Only happens when:

1. In 1st gear from stop or slow roll and I WOT floor the car, not in any other gear -

2. It lasts just for about a second or two until the car starts to move say past 30-35mph

3 There is no associated vibration feeling with the noise, it's just a noise. It does not sound tranny related.

4. my first inclination was exhaust tips or heat shields- all checked out ok and just had new mufflers installed (noise was same before new mufflers and after). I even took bumper and heat shields off to inspect!

5. it only makes the noise after car has warmed up. if the car is cold or not completely warmed up I can floor it from stop in 1st and no noise.

6. I cannot produce the noise when I rev it in neutral, so the noise is not RPM-related - only happens from stationary when I floor it under hard accell in 1st, and when the car is warmed up. I would say the noise feels directly related to the car pulling hard in 1st / engine load.

7. I checked my K&N filter but didnt notice anything loose, thinking it could be intake related -


Are there any air valves or something else that changes after the car is warmed up that could produce this noise based on hard pull / WOT in 1st?

It's tough to troubleshoot because the car has to be moving in 1st and under WOT / hard pull to reproduce, and I can reproduce it every time. The noise is very omnidirectional so judging exact location from inside the car is tough.

Suggestions welcome... There is one other pcar owner on Renntech with the same issue and he is baffled as well. His is a 2000 C2, mine is a 2002 C2.

 

Could it be the rear trunk latch or the spoiler?

 

don't think so, but I'll have a double-check anyway. The thing that makes this odd is it is not reproducable by revving the rpms (which makes most general rattles audible).
Definitely tied to 1st grear under hard accell from stop when warm.

 

Sound like you have bad rear wheel bearings.

 

congrats on 911 posts

+1 on this

 

Hmmm sure sounds like broken tips bracket,but you said thats been checked.

 

Thanks guys- I never considered that. from my past experience the noise does not sound like bad wheel bearings and does not exhibit bad wheel bearing typical behavior. (At least per experience with other cars I've owned). The sound actually makes you think it is exhaust pipe or tips related from the frequency / tone.

Shouldn't I feel it as well as hear it particularly at high speeds, and have the noise present under other conditions such as hard cornering?


3Deep - my tips do not have brackets, they only attach to the muffler down-pipe. I checked by tapping them and visually inspecting, but did not see any cracks etc.

 

yeah mine had cracked brackets and made that sound untill i removed the brackets.

 

^ where are the brackets? I have the turbo-style tips.

 

Looking at the pic. I see no nut on exhaust tip.

 

Good eye....you can see where the nut and or washer was there before and left the impression.

 

^ actually, that pic was taken when I installed the AP mufflers. Nut was taken off to adjust tips, and was refastened afterwards so it is in fact there.

Very good eye Daytrader!

 

My 99 does the same thing when excelleration WOT - sounds like something loose in stock exhaust (like a high pitch)or loose clamp or in EVOMS??? It is annoying but does not bother me all that much. Figure it is a good reason to update mufflers

 

Interesting you have a similar problem, does it only happen in 1st and when car is warm? Try it when your car is still cold and see if it is silent.

Mufflers were my first assumption, I have since swapped mufflers and same noise.

 

I had a similar type of noise on mine that drove me nuts... was vehicle speed dependent and louder as I drove around (warmed up)... ended up being my wheel bearings! FYI

David