Benz CLK 320 - Catalytic converter rattling

Hi folks.
My mom has a 2002 Mercedes CLK 320, and a few weeks ago a rattling sound started coming from underneath the car. It's mainly audible when the car is
idling in Drive or as it starts to accelerate. I checked underneath and the rattling is definitely coming from one of the two catalytic converters located near the center of the car. All the mounting bolts are secure, nothing seems loose, and the two cats aren't banging against each other (even though they're less than a millimeter apart). It seems like the rattling is coming from deep inside one of the cats. Any suggestions on what could be causing this, and if there's any simple solution to stop the noise? Thanks in advance!
- Logic316
"I don't mind what Congress does, as long as they don't do it in the streets and frighten the horses." -- Victor Hugo
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Yes, they break inside and rattle. Where are you? How many miles on the car? In the USA, they are covered under the 4 yr/50K warranty and in California, they are covered under the 7/70 emission warranty for noises.

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The car is under warranty by MB dealer... especially the cat converter due to federal law. Take the car back to them and have them fix the problem... apparently too much raw fuel got to the cat and burned it up.
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check to see if a heat shield has loosened up. They are just tack welded on & if the weld breaks, it can cause a rattle.
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