m a x i m u s

Hey, guys.

I noticed a couple of weeks ago that my car sometimes makes a strange noise. It sounds like a card in the bicycle spokes (sort of) or even like a (quiet) lawn mower. It is extremely faint and doesn't happen all the time. It can happen when the engine is cold, warm, or hot, AC on, AC off, high speed, lower speed, etc. It does, however, seem to only happen under power, so it goes away immediately when I lift. At first, I thought it might be an exhaust leak, but dunno. I tried as hard as I could today to reproduce the sound and then listen to where it was coming from, and it seems to be coming from the center armrest area. Also, when I did get the car to make the sound, I opened all my widows but couldn't hear anything (I thought the sound might echo off of the parked cars along the road, but no luck). I don't think it is something rattling around inside the car. Any ideas?

Now that I think about it, could it possibly be a leaking/damaged/bad catalytic converter?

Jasonoff

How old are your engine mounts?

Edition1c63

Exhaust could be hitting the K member. However, could be anything. When my longtubes were installed they were not as tight and would rattle very faintly on the K member. As soon as they tightened the hanger it stopped.

m a x i m u s

Not sure, maybe 30/40k miles?

Solo wing

1- I don't know about the w204, but in my old E55 there is a shifter-linkage bushing under the transmission tunnel. When it goes bad it produces a rattling noise. It drove me nuts.
2- Maybe the exhaust hanger broke.
​​​​​3- Transmission mount.
4- Broken catalytic converter rattling under load.


Good luck.

m a x i m u s

Thanks, Solo. For #1, what did that rattle sound like? My noise is def coming from that area, sounds very faint and like a card in bike spokes versus a metallic sound.

Solo wing

It sounded like marbles in a tin can.

hachiroku

maybe a plastic bag got stuck under your car?

RossN

Anyone fix this Noise? I just picked up a C63 and think I have the same noise.