My 1965 electra. Replaced the master cylinder and a broken line and bled the system. System is a single resevoir , power brake drum set-up. With the car NOT running , press the brake down and the pedal returns as normal. Start the car , press the brake down and the pedal stays down. wtf is causing that??? Maybe the power booster? Is their a spring in the power booster? If so maybe its a broken spring?? What do you think.
Sometimes... when a master cylinder leaks... some of the brake fluid will go into the power booster. When you start the car and apply engine vacuum to it the seals or valving has fluid in or on them and it won't release. I guess as a test you could start the car, depress the brake pedal, and then crimp off the vacuum hose to the power booster, and then remove the hose from the power booster and see if the pedal comes back up. (You crimp the hose so you don't have a huge vacuum leak when you pull the hose from the power booster and kill the engine).
So if I remove the master cylinder and look down into the booster, I should not see any brake fluid. Is this visual check good enough or am I missing something hear? When I replaced the master I did not see any brake fluid in the booster. Anybody else want to give me some help here?
When I bench bled the new master , the return spring seemed to work fine. Other than the return spring ,what else is there to cause my problems?