Did you buy new or rebuilt clutch and slave? If you had the work done at a MB dealer I assume they used new parts from the MB part system, but you never know. The new slave I bought recently from Fastlane was a Teves, and it had the Mercedes casting number cast into the cylinder body, so it is the same as the OE part, except in a Teves instead of a Mercedes box. (The problem with my original slave was pushrod wear - about an eight of an inch, and the clutch was starting to drag.)

One possibility is air is getting into the system due to faulty hydraulic component or seal.

Another issue could be bleeding. The clutch system cannot be bleed in a convertional way - by pushing on the clutch pedal and opening the slave valve. This is okay for fluid changes, but will not purge air from the system.

When the slave or master is changed you must bleed the system from the bottom up. You do this by connecting the RF caliper bleed valve to the slave bleed valve that is open about half to one turn with a length of tubing. You then open the caliper bleed valve while someone pushes the brake pedal - just like bleeding the brakes. This procedure injects fluid into the bottom of the system and forces the air out through the top where it vents in the reservoir. Give it about a dozen pumps, then close the slave bleed valve and try out the clutch pedal.

Duke