SLCPUNK

1994 c280 75k miles.

Sometimes when I put my car in gear it will make a humming noise. It won't do this when in N or P, but will in all other gears. It's almost like a humming/buzzing sound. It goes away in a couple of minutes once the car is warmed up. It has me concerned though because I know it's not going to go away on it's own. Last transmission/converter change was 10k ago.

Does anybody have any ideas what this may be?

Thanks

GDawgC220

Is it like a "cycling" sound from the rear right of the car? There's a pump back there in the lining that makes that soun when your in any gear besides P and N. It makes that "cycling" noise then goes away after a little bit. Still haven't figured out what it is, I have my radio up anyhow, so I don't really hear it

But that seems to be normal on the w202s...goes away after the car is warmed up.

pointman

ceramic monolith inside the exhaust sytem is breaking up... it is not really a problem unless the pieces get to large and restrict the exhaust.

SLCPUNK

Why would the noise go away after a little bit ? And why only in gear , not P or N? Thanks.

SLCPUNK

Hey GDawg. Only thing is that it hasn't made the sound before. Just recently.

pointman

honestly i couldnt tell you...but i am confident that this is your issue. to verify, get underneath your car, better yet get it ona lift and hit the exhaust piping with the backend of your hand...run from the front end all the way to the back, at one point you will be able to replicate the noise.

SLCPUNK

Cool I'll try it tomorrow.

GDawgC220

but my noise isn't from the middle or anything...if you open up my trunk and lift the carpet...u can hear it right there. It's like where the battery is, the aux pump is making that noise.

let me know what you find man. I'm certain this noise isn't my exhaust.