craigmurray

OK, I need help. I have a 2003 C320 coupe with 111,000 miles that I bought used at 105,000 miles.

I hear a rattling noise from under the car, have to have the windows rolled down or it cannot be heard. I can hear it when in park, neutral, or drive. When I have the car in park and at idle there is no noise, when I give the engine gas the noise starts and gets loudest at lower RPMs fade away as the RPMs increase.

Last week I changed the oil/filter and transmission fluid/filter. It is an automatic transmission. I also corrected a couple of ATF leaks, the piolt bushing and a fitting on the radiator. I was concerned that maybe the noise was in the tranny but since I hear it in park, neutral, and drive this does not point to the tranny in my mind.

What could this be? I am leaning towards exhaust shielding.

Can the tranny make noise when in park and neutral when giving the engine a little gas?

tommy

I would think of what you are, the heat shielding or even the cat itself. You're about at the mileage where the cat will self-destruct.

Dingleberry

Key areas I would inspect: Heat shields, catalytic converters, motor & trans mounts.

MW_ATL

I had a similar sound under mine, turned out road debris or something had bent the exhaust pipe just enough it was touching a bolt head.