why wont my brakes work!!!

[broncomitch]

k heir is the thing. i had a hard brake line blow out on my max, (rusted out) so i replaced the rusted lines and bled my brakes, worked good for about 2 days then had nothing again, fluid was full and no leaks so bled them again got better then 5 mins later nothing, long story short i bled them 9 times and i took it to my mechanic and he pressure bled them 4 times. they worked perfect after that. but a week later there just as bad! only the right rear is getting pressure. so all that is telling me its the master cylinder but i cant see how it worked good then blew the line then it besides to go bad.

anyone have the same or similar problem? or what do you think it could be?

[maxhopper]

My guess would be that air is getting into the system somehow. I would also think that if air could get in, that when pressure bleeding the system the fluid would leak out. Have you checked to make sure the brake booster and master cylinder are good?

[robo_geek]

If you leave an old master cylinder alone, it lasts forever.

IF you pummel it with a pressure bleeder, or stir up the flotsam inside by foot-bleeding it, it will fail.

Under normal use, the pistons/seals travel over a small section of the cylinder bore. When bleeding, you push those old rubber seals over territory that is likely not so smooth and clean....tearing those old rubber seals.

I bet if you look real close at the brake-pedal end of the MC you can see fluid leaking out.