Thanks, I would be interested to know what information the factory CD has re the clutch master cylinder, especially the issue of a master cylinder pushrod adjustment that the Haynes manuals discusses. Mine definitely does not appear to have any such adjustment with the master cylinder itself being the stop for the pedal in the up position.
With time (since my thread of some months back) I have been able to observe and analyse the problem. The clutch definitely checks out OK using the measuring tool. When cold it works fine without any hint of slip, even under full throttle conditions. The take-up point is fairly high in the pedal travel but not at the top. After considerable time driving (in warm weather), the take-up point gets progressively higher to the point where clutch slip begins to occur even at moderate throttle openings (can still be driven under cruise conditions but care must be taken to avoid slip climbing hills and accelerating). When everything cools down again all is fine. On my short daily commute it is not a problem, nor was there any obvious problem through the cooler months of winter. Only now with hot weather coming and on longer journeys is the problem again becoming obvious.
I am convinced that the inlet port (from the reservoir) in the master cylinder that should be uncovered when the pedal is at the top of its travel is remaining covered. This is normally taken care of with the pushrod adjustment that the Haynes manual describes. If the port remains covered by the master cylinder piston, pressure build-up that occurs as the temperature rises, cannot be released by allowing excess fluid to return to the reservoir. In the absence of a pushrod adjustment this can only occur as a result of something blocking the port such as a swollen piston seal or foreign matter in the port. The pressure causes the slave cylinder to hold the clutch slighty released, resulting in the slipping.
I was hoping that someone my have dealt with a similar situation or can at least agree with my diagnosis. It would be easier to overhaul or replace the master cylinder than to replace the clutch, especially if the clutch is not worn out (as I am inclined to believe to be the case).
Thanks for the thoughts on the problem,
107.023: 350SLC, 3-speed auto, icon gold, parchment MBtex (sold 2012 after 29 years ownership).
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