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.
Rattle From Beneath Vehicle on Mercedes-Benz CLK430
Average mileage: 65,862 (11,000–100,000)
21 people reported this problem
2002 Mercedes-Benz CLK430 35,535 mi, Visitor
I STILL THE PROBLEM. DOES ANYONE KNOW HOW MUCH THE REPAIR WOULD COST?
2002 Mercedes-Benz CLK430 85,000 mi, Visitor
rattle under car, took it to a local muffler shop and said back passenager side cat is bad.
2002 Mercedes-Benz CLK430 27,000 mi, Visitor
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.
2002 Mercedes-Benz CLK430 69,000 mi, Visitor
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
2002 Mercedes-Benz CLK430 70,000 mi, Visitor
It rattled while hitting gas. I put an American made aftermarket. (Thunderbolt)
One of the rear cats is rattling and requires replacement.