This is a new one on me...I just bought another W123...and after the second real drive for any miles..I heard a noise in the back the sounded like a cable wrapping around something...then the right rear wheel locks up...then lets go. My kids were 15 miles behind me, so I pulled over. We assessed the situation and the noise was coming from the right back wheel....clank, creak, clank at slow speed. I thought it was a CV shaft falling apart or the parking brake drums, but it was from the wheel area. But, the rotor still looks good on the outside. I followed my son driving my 300TD with me driving his 300D for 26 miles, pulling over routinely for possibly overheated rotors (brakes never failed or seemed to be overheated.) He mentioned the right rear grabbed several times as was my initial condition. Sounds kinda like collapsing brake flex lines...but why the dramatic noises? In the '89 Earthquake in San Francisco I lost the caliper off the hub and it made similar noises in a '78 VW Diesel.