ok, so Ive been losing my mind on this, and I dont want to just throw parts at this: stock booster newer rebuilt single master I do not leak fluid as far as I can see losing fluid in the res brakes are good as soon as I replace fluid when it runs down, I get super soft pedal no brakes pedal returns everytime so I know booster is good when I replaced the master a few months ago, everything was good for a little while, brake fluid was in the booster but not past the boot so it never made its way completely inside any ideas? Thinking bad rebuild as Ive seen it before not getting air in the system as I dont have to bleed, just add fluid to get my brakes back thanks
Leaking master. Pull it loose from the booster, pull out the pin and rubber surround and make a dip wick out of a clean paper towel and see how much brake fluid is in the booster. That's the problem I had with my '60 deVille. I had to use a Mighty Vac air powered brake bleeder to vacuum out all the fluid. Get a rebuild kit for it and re-do it yourself so you can see the condition of the bore.
Are you positive you don't have a leak somewhere else in the system? No brake fluid on the back of any of the tires or other signs of leaks? I just went through that with my mom's mid 70's Ford pickup. She said my brother was adding brake fluid quite often and thought the master cylinder was bad. I got down and looked under it and it ends up that one of the front calipers is leaking. In other words, check the whole system out before you replace anything or spend any money. If that is still a single master cylinder they usually rebuild quite well as long as they don't have pitting where the cups on the piston slide.
Replaced the master......and........Everything is golden so far. brakes are good, I took it for a nice long ride and no issues