Trying to repair ATE tandem master cylinder

[karshack]

Before I delve into changing a lot of my brake parts, I decided to get a used spare ATE master cylinder to practice tear-down and reassembly just in case I find that there are probs with the one on my car. My 1967 250S originally came with the Version 3 of the MC. Versions 2 and 3 are virtually identical (a difference of 1mm in pushrod travel, and the stop screw area on the bottom of the body has either a sharp or gradual flare).


So, here is my problem: I can not remove the Piston (pushrod circuit) for some reason that I can not devine. I have placed it in a vise and pulled on the body. Lifting it and a 60-lb workbench about 6-inches in the air. And the piston does not budge - and that's after having used lots of WD40 and Liquid Wrench. I can not see how to remove what looks like a white plastic washer - see pic. I don't want to destroy it, because I do not see such a washer in ATE master cylinder kits on the web.


Any suggestions would be greatly appreciated.

[97 SL320]

WD-40 is a miserable lubricant / penetrant.

The piston pushes in correct?

I don't know this MC specifically, but I've seen pins in the ports where the reservoir attaches, the are usually under the grommet.

Other than that, I'd place a long socket / tube over the piston so it contacts the washer and give it a few hits. But not too hard as we don't want to mushroom it and lock it in place.