72 f-350 brake trouble

i have a 72 f-350 and the brakes are really bad they have fluid and it dont leak i have blead them many times but it get the same way after a few min what else could it be :banghead:

i have a 72 f-350 and the brakes are really bad they have fluid and it dont leak i have blead them many times but it get the same way after a few min what else could it be :banghead:


When you say there 'bad' does that mean there very hard to push or that the pedal goes to the floor?

Thanks,
Stan

Change the Mater Cylinder

straight to the floor