2000 S430 loud rattle in the exhaust near cats
 

Wtf any ideas?

sorry for the verbosity... posted it from my phone.
the car has a nice smooth engine, but there is a very annoying rattle in the pipes, near the center of the car, in front of the resonators/cat. the pipes are not loose or touching anything, but it sounds like there is a socket or something rattling inside...
perhaps something came apart inside the pipes?

OK, several threads about the cats failing, and causing the rattle... good old search!
I'll check with the dealer and see if any extended warranty is in place, but it's unlikely.

does it do it in park or neutral.reason I asked I have exhaust rattle in drive or reverse,and I have not cats or middle mufflers.

it does it in park/neutral.

had the same problem on my 190e.....I'm sure you can hear the rattle even more if you accelerate. The problem is most likely the "honeycomb" inside the cat is loose. Since my tags are good until 6/13 I had my friend take out the cat and I will just get a new one once I get closer to my next smog check date. a way to test it is to life the car up and go bang on the cat with your fist, engine off. You will probably hear it rattle inside.

Tapping on the cats with a rubber mallet is a good test.