My brakes are soft and not building pressure

MIKEMILTON1996

MEMBER
1995 FORD MUSTANG
3.8L
V6
AUTOMATIC
190,000 MILES

ABOUT 2-3 WEEKS AGO I MY BRAKES STARTED GOING TO THE FLOOR I WAS ABLE TO PUMP THEM AND STILL STOP THAN ABOUT A WEEK AGO THEY STARTED GOING ALL THE WHY TO THE FLOOR. SO I HECKED IT OUT AND MY RIGHT REAR CALIPER SEAL BUSTED I CHANGED IT OUT AND TRIED BLEEDING IT AGAIN NOTHING CAME OUT THE REAR CALIPERS SO WE CHANGE THE PROPORTIONING VALVE AND SOME LINESHOPING THE FLUID WOULD GET AROUND BUT MY BRAKES ARE STILL HITTIN THE FLOOR AND NO PRESSURE IS BUILDING UP I'VE BEEN OUT THERE FOR A WEEK STRAIGHT DOES ANYONE KNOW WHAT I CAN DO

1 Reply

CARADIODOC

MECHANIC
33,916 POSTS

Your description is real hard to follow, but a common cause of a slowly-sinking brake pedal is a bad master cylinder. Also, regardless of what caused the pedal to go to the floor, doing so will usually damage the master cylinder. Crud and corrosion build up in the lower halves of the bores where the pistons don't normally travel. Pushing the brake pedal over halfway to the floor runs the rubber lip seals over that crud and rips them. That results in a low or slowly-sinking pedal, but often that doesn't show up for two or three days.