2006 f250 FX4, The right rear caliper froze up and started smoking. 10 minutes later I went to move the truck to work on it and the pedal went to the floor, no brakes what so ever. I replaced the caliper and both rear pads, bled the brakes. Now I have marginal brakes and very low pedal. I can't figure why I lost all braking. I replaced the master cylinder today and still have a low pedal. Any ideas?