Petur, earlier in the thread mention is made of the "double lipped seal." I may have bought the last one available from Tom Hanson at the Classic Center recently. Seems these are only used on the W109 cars with the two pumps linked. Perhaps Tom was successful in having a new batch produced. Good Luck.
I just read through the compressor repair. Nice. What I am missing is the bronze bushings that potentially need to be exchanged if worn. This is for a higher mileage compressor or one that had problems with lubrication. I have seem some of the compressors in not that great shape as the one here. Some have 2/10mm play in the bronze bushings. Knorr was using 2 types of bushings.. High leaded Bronze (15% Pb) for the softer Crankshaft bushings and 'Rotguss'for the hard piston pin in the piston rod. These bronze bushings are not part of the MB kit. These bushings need to be machined with 2/100 play for the rotating shaft and press seat for the seat itself (2/100). Typically the cylinder requires some honing and piston with new rings for a higher mileage compressor. Martin
Here is another aspect to consider. Testing the check valves
I have renovated various compressors. In my humble experience the tightness of the compressor determines the power of the compression and suction. This means if the check valves are not closing properly even the best renovated compressor is not pumping well. New check valves sometimes are not tight enough and I developed my own testing protocol. I have not experienced how slightly leaking new check valves are improving or not over time. Whenever I renovate these compressors I am testing and work as long as it takes to have the valves working properly. The tightness of the piston rings/cylinder is important too but the check valves come first.
It's just an old fashioned air compressor with a hydraulic pump screwed on to it. The real complexity, as we all know, are all the components "south" of the compressor. We are fortunate to have Martin, who's remanufactured components are arguably better than the OEM's.