1972 n600 brake problem

[SteveC]

My father has a brake problem on our n600 it has little to no brakes. We are not losing fuild but the brake pedal just goes to the floor. You can pump up the brakes and hold your foot on the pedal it slowly goes to the floor. If the engine is running its like their is no pedal at all their is no resintence. It has a vacum booster and master clynder on the firewall.

Is their any ideas or diagrams were we can start.
THe master clynder has been apart and honed and cleaned.
Is this maybe a vacum booster bypassing
We think is a midland or a bendix he said he is pretty sure its a midland though.

Sorry for this being a mess and thanx for your help.

[fordman]

that sounds like the maser cylinder is leaking back into the booster. but if it is then the engine would smoke bad if the booster was still working good. does the truck also have a helper booster under the cab step?

[ToughOldFord]

That master cylinder is junk, don't mess with the honing/rebuilding route, that fails more than it works. Just replace it.

[Thunderfoot]

the booster would not effect the pedal going to the floor but the master cylinder piston not sealing would. Why it does it so easy with the motor running, is because the booster is working, doing it's job, making the brake pedal push easier (more pressure) to move the piston and if there is no resistance (pistion not sealing) then the pedal will go right to the floor with ease...