'01 C320, 30K miles, clunk/thunk (metal hit metal sound)seems to come from rear of car. Happens only after the car has been driven over an hour and not all the time. Once it starts it continues until car completely cools down. It occurs when braking from any speed above 40 mph and happens at about 20 mph...or sooner if I depress the brakes harder. No matter how softly I brake it occurs.
???

................quite a coincidence. I had the exact same problem. I took my car to the dealer. They told me I had warped rotors and since my rotors were aftermarket rotors, they blamed it on it and wanted me to get new front and back MB rotors and pads. I was skeptical. I went to a MB performance shop........it took them 5 minutes to tell me the real problem. I had uneven were of the the front tires due to the car not having a good alignment. Well, because it seemed that the noise was coming from the rear I was also skeptical, but I replaced my two front tires and had an alignment and the car drives perfectly without any noise. I inspected the front tires that were removed and it turned out that the inside portion of the two tires were totally worn. I suppose it is possible that we both don't have the same problem but your description of the problem sounds exactly like mine.

Ted

Hmmmm...had my car realigned at about 13K miles because steering wheel was crooked. I rotate tires every 5K miles and wear is always even. Noise didn't start until about 23K miles. I won't discount anything but both warped rotors and alignment sound far off the mark. Obviously the alignment worked for you. Thanks for the reply...anyone else have similar noise fixed?

............I understand. I don't think it was the alignment that fixed my problem , but the replacement of the tires did. The alignment was to prevent it from happening again. Good luck.

Ted