knock noise
 

My 2002 E320 4matic wagon just started making a knocking noise. It has 34,000 miles and the noise sounds like it comes from the catalytic concverter area. You hear it at idle and seems to disappear when accelerating. I guess I will have to put it up on my ramps and start it up. Can anyone please offer some suggestions? Thanks in advance, John

Answer:
 

Possible bad catalyst.






Have a great day.

If it is a bad cat, it's still under warranty, as emissions equipment warranty is 8yr/80K miles, always transferrable.