It has original brakes so no power assist. When I replaced the master I bled the cylinder at the connection to the brake line (the line had fluid at the end and so I bled at the connection point). I am not aware of doing damage to any cups in the master. I.E. if a wheel cylinder ever was to blow the brake pedal will go to the floor so I can't understand why it would be make that way.
Also the surge of fluid is when the pedal is compressed, not released.
I checked with a local mechanic and he verified the squirting is normal, but I do know the cap should seal the fluid from coming out but do not know if there is supposed to be a gasket or "O" ring on the cap?


1953 Chevy 153A 3/4-ton
Working on my project since 2015
Follow along in my DITY