Brakes soft then hard brakes


New Member
Aug 20, 2009
88gt have a 93 cobra booster, 04 cobra front brakes, cobra irs rear brakes. i cant remember what master cylinder i have but im pretty sure its the correct one. got rid of the plunger thing in the proportion valve and have the ford racing adjustable one for the rear brakes. ( have the all new or fairly new parts within 20k. i just put on new front brakes because the calipers needed rebuilding because of sticking. conformed that when one wheel was hard to spin and the brake pads were wearing down unevenly.

my problem is the brake pedal is soft for pretty much half way (only light stopping force) then become hard as a rock. before i put on the new front brakes the pedal was just always hard to push, it wasn't always like that they were normal stopping brakes for a long time, something happened(stuck caliper).

ive checked vacuum, kinda low at 16 at idle, pulled the brake booster check valve after turning off the car and i can hear the release of vacuum.bled brakes no air bubbles.
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WAIT,you now have a pair?
10 Year Member
Apr 3, 2009
If you let the master run empty while doing calipers you must bench bleed the master,and bleed it well.