Driller

With my '99 SLK 230 w/ 5 speed manual, there is a rattling sound between shifts when the driveline is slack. I can also create the noise when I feather the throttle at about 4,000 rpm again, trying to get the driveline in a neutral/slack position. The dealer has replaced the propeller shaft and both front engine mounts. They now believe that there is something rubbing/vibrating near the driveline.

Any thoughts would be greatly appreciated.

mbtech208

It sounds to me like either a loose exhaust heat shield or a catalyst coming apart internally.

Driller

Thanks for the quick response, I'll mention to my dealer...and to add a bit...to me, it sounds like rattling u-joints of cars gone by.

2quik

My guess would be catalytic coverter, very common problem

Driller

I agree, although it has been changed out once already...but for a different reason. If my memory serves me, I believe that this rattling sound was there prior to the new cat. Thanks very much for your input though!!

Driller

Now my service advisor thinks that this rattling noise is the air valve vibrating when the S/C is not engaged and/or the engine is not supplying any torque.

Does this sound plausible MBTech?

mbtech208

I've never heard of it before, but that doesn't mean it's not possible.

230KBenz

On a 320 the cats fall apart and rattle, but on a 230 we have done some with loose parts or something inside the rear muffler.

2003 c230k magma, c5, c7, 6 spd.