Brake power loss

[hamersmt]

So i have been driving with an inherent issue for the last 3 months, and decided it is time to finally take care of it.

Backstory: i was losing brake fluid, didnt know where it was going as there were no drips under the car, so i went forward and just replaced the master cylender (NOS) and bled the brakes figuring this would solve my problem.

Present: The problem i am now having is that there isnt any pressure the first time the brakes are hit, but a quick pump and the pressure is there. I know my rear shoes need replacing, but i also have brand new rotors/pads up front. I am also still losing fluid, and i have to top it off everytime i fill up with gas.

Could it be that it is dripping somewhere and evaporating without my noticing? Could it be that the new mast cyl is damaged?

I do have a brand new master cyl re-build kit i was planning on using on my old cyl. So maybe that would solve the problem?

Im stumped...

[jmortensen]

Probably master cylinder leaking into the brake booster. You can pretty easily pull the master forward enough to see in the booster. If there is fluid in there drain it out, and it does sound like you're needing a master.

[chaztg]

I think the new master cylinder has a receiving cup on the back which is deeper than the one you replaced it with. The pin that sticks out of the vacuum booster should be sticking out just far enough to fit into the back of the master cylinder, but if the pin-cup distance is wrong, when you apply pressure to the brake system there is that little bit of distance to make up and it feels like the pedal has no pressure until the second time you apply it. Remove the new master cylinder from the booster without disconnecting it from the hydraulic lines and peer into it to see if the cup like thing in the back matches the one that came out of the car (if you still have it). I've seen them both deep & shallow; I've also seen different length pins in the vacuum boosters in other Z cars I've worked on. The pin is threaded for some adjustment, but be careful. Sometimes they're very difficult to turn. There may be corrosion and it could be fused so if you shear it off you're screwed. Best of luck