Originally Posted by bscott2960
I have a 97 F150 4x4 with ABS rear brakes. I just put on new pads, shoes but then the pedal was really soft despite bleeding the brakes a few times. I replaced the master cylinder and now they will pump up but as soon as I start the motor the pedal goes to the floor. Also the ABS and emergency brake light now stay on. Any ideas?
Reinstall your original master cylinder, there was probably nothing wrong with it in the first place. Check all the calipers/wheel cylinders for a leak. If it has disc brakes all the way around look for a stuck caliper or very funny brake wear on one of the corners like the brake pads wearing unevenly.
I have come across this problem numerous times and it was lack of lubricant on the slides for the calipers.