I re-read all the posts last night. I also looked on the 124 CD and my other manuals in vain for a cut-away of the master cylinder. The C-class Haynes manual has some excellent pictures of the MC and SC disassembled. It also states that there is no adjustment so I think the 202's have your setup.

It states "...as wear takes place on the friction disc ..., the pressure plate automatically moves closer to the friction plate to compensate." Huh? How does this work?

Anyway, here are my candidate theories at this point in descending order of (my) probability:

1. Corrosion in SC after 13 years without fluid change has partially blocked the line connection preventing full fluid return.

2. Flex line deteriorated, not allowing full return.

3. Metal line damaged or corroded, same result.

4. Check valve in MC malfunctioning not allowing full return.

5. Obstruction in pedal mechanism not allowing MC piston to return fully, blocking hole to resevoir.

6. (New theory). Clutch wear or malfunction of mysterious self-adjustment mechanism is causing the the MC piston to not return fully, blocking hole to resevoir.

Can you somehow test 5 and 6 by verifying that the MC piston is returning fully up against its internal stop?

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe