Headeater

Can anyone help me out? I have a 2009 C300 Sport 4matic with 64K on the odometer. Have had the car since new and the brakes sensor came on to replace the brakes. Sounded easy. I have changed brakes numerous times on vehicles but am stumped here. The new rotors and pads went in without a hitch. I removed the calipers from the car so I could put the new pads in on the bench and clean the calipers. Put everything back together, did not rebuild calipers, and it looks good. Used a one man vacuum pump to bleed lines which did not work so got a friend to pump brakes and then I bled them. The pedal kept fading but no air in lines. Went to auto store and they said master cylinder must have flipped the seal when I used the pump and I would need to go to Mercedes for new master cylinder. Off I went and have replaced the master cylinder but I still get fade and cannot figure out what is going on. Anyone have suggestion? No leaks anywhere so I do not believe that to be the problem.

RLE

I haven't done this myself yet but I believe the experts say that pumping the pedal in ABS/Traction control cars does not do the job. Is there a chance that you reversed the calipers side to side which can be done on some cars which relocates the bleeder valve to the bottom? I don't know if that can happen on our cars, though.

Did a dealer replace the master cylinder?

I wouldn't ask advice from a parts shop salesman when it comes to MB problems.

Doanster

By fade do you mean the pedal goes all the way to the floor (or close to it)? Also, who replaced the Master Cylinder? The dealer? Assume they bled the lines and replaced the fluid? If the dealer didn't do the replacing, then whomever did may have not bled the lines properly once again since you say there are no visbile leaks.