there is not a rebuild kit for abs valve or RABS valve it tried to find it only found new one at ford and it was 450.00 with the 200.00 core dont have much time i will holler back at ya

 

cant find the Ford # for the booster. There was a TSB that referenced a "creeping" brake pedal. Ford said the creeping was "normal" and sent everone on their way. later on and after many complaints they offered a redesigned booster that eliminated the creeping of the pedal while stopped and at an idle. Many problems with the brake pedal leaking down were fixed with replacing the RABS valve. Some were fixed with replacing the master cylinder. Also there is more than one # listed for a master cylinder on these trucks so you have to make sure you have the right MC, the bore size differs with the gross weight. Externally they will look the same. Also, remember that a diesel engine doesnt produce as much vacume as a gasser so you have to make sure that the pump is producing enough vacume to run the brakes. As for the rear brakes "hanging".. jack up the rear wheels and apply the brakes.. see if you can spin the wheels by hand... if not, crack the bleeder on the wheel cylinder and see if fluid squirts out. Find out if its both or just one side that is grabbing. Go from there and trace it up stream from there.

 

I'm waiting in the wings for the answer to this problem because I too have a spongy brakes. I have an '86 E350 with 6.9 diesel and C6 transmission. I've changed the rear wheel cylinders, booster (rebuilt), master cylinder and still spongy. It will stop but not a positive feel to the brakes.

 

check vacuum output from your vacuum pump should be 17-21 hg a old cheaper vacuum gauage will do try to tap in at the pump first to get a base reading then at the booster itself, did the booster come with a new check valve if not replaced it and get in the floor board for sucking sound. did you make sure the m/c you put on is the same one you pulled of bore size and piston recess hole where rod fits are the same length and how about rear brake adjustments reply back when finished