The first pic shows the cap for the hydraulic piston. This has a hole where formerly the brake light switch was placed. I capped it with a 3/8 fine thread plug and a 3/8 fine thread jam nut. Works great.
The second pic shows the hydraulic cylinder end gasket, the piston, bottom gasket and the spring cup ready to be reinserted.
The third shows the removal of the control valves and the kind of crud I found there. They cleaned up easily with paint thinner.
In the end, it appeared that everything in the second air pack had been replaced new, was still in new condition, other than surface rust, and after cleaning I reassembled it. I did use gaskets and the spring from the repair kit where needed. The main problem appears to be the use of too much gasket sealer and a lousy paper gasket for the air pack cap.
After I get the new square o-rings I think this air pack's problems will be solved. Well not quite. It will take extremely narrow o-rings because of the studs welded to the sides of the air cylinder mean the gasket will have to be exceedingly narrow. I will give McMaster-Carr one more try before making my own paper gaskets.