Brake pedal goes to the floor slowly on 1994 Ford E-350

I have isolated the front from the rear and determined the front is the cause to the pedal bleeding down. I bleed numerous times. Booster works perfectly, no air leaks. Only rear abs. I also replaced both calipers. To isolate the front, I disconnected the rear brake line from the master cylinder and plugged it. Pedal goes to the floor slowly. I disconnected both lines from master cylinder and plugged. The cylinder locks up, no movement.

by in Markham, IL on October 27, 2011
2 answers 2 comments
ANSWER by on October 27, 2011
from your description, either you have air in the lines that is being stubborn, a leak in the front or a bad master cylinder. Roy
ANSWER by on October 27, 2011
Use brake line clamps to block off each front caliper at the brake flexible hoses just to eliminate the front calipers/caliper mounts being an issue. It is likely to be a bad brake master cylinder.
COMMENT by on October 28, 2011
Thanks for the tip. I took your advice and clamped the lines. I had no pedal drift with the lines clamped. I have bled the calipers, but is there any special bleeding techniques for a caliper? I removed the left and it bled down. I clamped the left and removed the right, it bled down.
COMMENT by on October 28, 2011
you may need a pressure bleeder to force the air out of the system. Roy
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