Brake pedal bleed down

[Madgyver]

I having this problem with all around drums on the firebronco. It has a power booster (vac PO installed) and 4 corner stock drums. The bronco stops but while holding the brake pedal, it bleeds down. There is no visible line leaks so I'm thinking internal leak, bad master cylinder.

Your thoughts before I dig into it when I get some free time.

 

[fastcarkenny]

I agree. Sounds like the seals in the master cylinder are bad and letting it bleed down.

 

[dbevans2249]

Mad it is more than likley the master cyl. If you unbolt it from the booster and slide it forward you may be able to tell for sure. If there is no sign of a leak there it could be a wheel cyl.