You guys are my last hope so here goes. 1993 F150 4x4. The truck has a hard brake pedal till i start it up and then i goes straight to the floor. The Problem Started out as a hanging caliper. Replaced pads and away i went. Half way home my pedal went right to the floor. Bled the brakes and not any better. So bought a Master cylinder and bench bled it, put back in and no better. Said hell it started with a hanging up caliper so ill replace them and the hoses that go to them. Did that and rebled and still no better. Figured the master i got must have been bad so got another one. No better. Bought a booster and still no better. All the lines on the truck have been replaced but 2 and theres no leaking. I have bled the proportion valve and abs valve. I'm at a loss. Everyone i talk to has no answers.

Any Ideas would be great.

oh If i push the pedal to the floor while driving i can get the right rear to lock up but that is it.

 

try sending a p.m. to "andym".

go to:

https://www.ford-trucks.com/forums/m....php?do=getall

then put in california for state and over to the right type in "andym"

in that list he is 3rd or 4th.

 

I would guess the first time it happened you had a master cylinder failure. I would further say that the problem now is the system is full of air. I would make sure the rear brakes are fully adjusted up and then bleed the brakes again.

 

I'm having the same problem with my 95 250 PS. I haven't changed the booster or vacuum pump yet. I was going to change calipers, but maybe not now. Mine started with a stuck caliper as well. Got it unstuck and put new pads and it hasn't been the same since. Put in new master cylinder as well. Bled the thing at least 3 times. Same exact problem, but my pedal is a little soft with engine not running.

 

I guess I'll check on adjusting/replacing rear brakes. My Chilton Cd says there's a sensor, and the rear have to engage good before front will at all.

 

Don't forget to bleed the RABS valve on the frame under the drivers feet.. Since you replaced the master cylinder there is a good chance it has air in it..