My 85 300d has a popping noise that occurs on bumps and when breaking the vehicle. I had a MB mechanic take a peek and he said everything looks fine underneath. When you test the shocks they don't make the noise while parked. Someone else mentioned that it could be the brake caliper.

IT'S DRIVING ME CRAZY!!!!

Are you sure it is not coming from the pipes leading to exhaust?

My 300D project car
 

does it too. I am under the impression that the ball jts. need replacing on the front and when I look around with the tire removed it looks like the majority of the rubber bushings are shot. The upper control arm bushings look especially tired. All of these items are on the "to do" list.
Jim
'85 300D
'95 E320
'97 CRV

I am sorry but this is too funny to pass up. You hear a popping noise when you BREAK the vehicle? It's probably the sheet metal cracking!

Well I have kind of the same problem when BRAKING the vehicle. Does your noise sound like it's coming from the front? Like the shocks or something within the steering mechanisms??

Yes! It comes from the wheel well. Remember my mechanic on a quick check everything looked good. Even the bushings

I have a similar problem. Mine usually occurs after I start the car, begin to drive, then I brake for a stop sign, and it "pops" but will not do it again for atleast a day. Usually only when I am leaving work... where my car is in the sun... heat related somehow? Maybe we have a similar problem.