I have a 1998 Ford Expedition that has a soft, spongy brake
pedal that travels too far. The stopping distance is dramatically increased under this condition. With the engine
off the pedal builds up sufficient pressure when pumped, but loses pressure and goes nearly to the floor when the engine is started.
I've tried the following in order to fix the problem with no improvement so far.
1) Checked fluid level in master cylinder reservoir....ok.
2) Bled brakes at each wheel starting first at the wheel farthest from the master cylinder and ending at the wheel closest to the master cylinder....with no noticeable improvement.
2) Replaced master cylinder, bled brakes again....with no noticeable improvement.
3) Checked vacuum to master cylinder with a reading of about 15 inches of vacuum. Then I pulled the check valve off the power booster and it was flowing correctly in only one direction.
4) Replaced power booster....with no noticeable improvement.
5) Replaced front brake calipers, installed new pads and bled both front brakes....with no noticeable improvement.
I'm at a loss of what to try next....does anyone have any suggestions?