First thing I would check is whether the slave cylinder is actually extending when you step on the clutch. Have someone engage the clutch while you watch. If the slave is actuating but nothing is happening inside the bellhousing then you either have a broken pivot arm or a missing throwout bearing or something like that. Don't know if MB bellhousings have any kind of access hole you can look thru to see what is happening inside. But if the slave is actuating and the clutch is not disengaging you're going to have the pull the transmission to solve the problem.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13