Rattle From Beneath Vehicle on Mercedes-Benz CLK430

Problem Description and Possible Solution

When the engine is running, but the vehicle is not moving, a rattle heard from beneath the vehicle could indicate that one of the exhaust catalytic converters has failed. The substrate (the internal part of the catalyst that reduces emissions) can loosen and bounce around inside the canister section of the converter—the defective unit will need to be replaced. If this problem is ignored, the substrate can break down and reduce to a size that plugs the outlet pipe, which will cause a sudden loss in power.

Problem Data
RepairPal Verified
Average mileage: 65,862 (11,000–100,000)
5 model years affected: 1999, 2000, 2001, 2002, more2003
21 people reported this problem
Viewing 1 - 8 of 8 comments
rattle under car, took it to a local muffler shop and said back passenager side cat is bad.
Still have not fixed it. There is an EPA warranty on this, depending on the mileage, but they wouldn't cover it because my vehicle (which I purchased used) came in through Canada.
There was a cracking sound coming from under the car on the drive side while the engine was running. It was checked by a mechanic and he confirmed the catalytic converter was bad.
Had converters replaced 2 times this time a mach told me its the after converts that rattle while moter is ruining 2002 Mercedes clk 430 8cly started making noise 1 year after front converters was replaced around 64000 miles I now have about 67000 miles on car garage keep in winter the first time front converters got replaced by mercedes the car had onley about 24000 miles
It rattled while hitting gas. I put an American made aftermarket. (Thunderbolt)
rattle on deceleration. replaced converters.
One of the rear cats is rattling and requires replacement.