Soft/Low Brake Pedal
I have a 56' ford f100 with power brakes. Always felt that the break were not right as the pedal always got really low to the floor. This past month, the master cylinder began leaking. Replaced it with a new one, which was a 1" bore master cylinder from a 79-81 Buick Riviera.
After bench bleeding and installing, vacuum bled the lines, the pedal could be pushed to the floor with my hand without the engine running.
First I thought the new master cylinder might be bad. To test it out I removed the rear brake line and plugged it. When I did so, I tried pressing on the brake pedal and there was almost not movement.
This has me thinking that there is something going on with the rear brakes. I have a 10lb residual in the line. I was also asked by the auto parts store if it was rear drums or disks so I got the mc for the drums.
I believe the drums brakes are adjusted properly as I can hear the pads drag on the drums and it is difficult to rotate the rear tires by hand.
Only thing I can think is that the rear flex line is ballooning, but would that cause such a drop in the pedal?
Any help or other ideas would be appreciated.