I have a 2001 F-150 I am repairing for a friend. I have replaced all 4 calipers. I was able to gravity bleed the front brakes no problem, however I can not get any fluid to the rear calipers even with a helper pumping and holding the pedal while I crack the bleeder. The pedal just goes to the floor. Seems like a master cylinder problem but it had a decent pedal before the old calipers where replaced. I have no experience with newer vehicles as I am an old muscle car guy. Any advice is greatly appreciated.

 

I hope you already fix your buddy's truck by now, if not I hope this helps. With ABS it is best to use a pressure bleeder and start at the furthest from the master cyl. Using the pedal method can cause issues like the valve slide to lock off that wheel cyl (like the cyl blew a seal), If this happens close the valve check to insure there is fluid in the Master, then stab the brake pedal the valve should reset and the brake light go out. Once everything is reset and you insist on using the pedal, push gently and slowly. Hopefully avoiding this issue...
Mike/EZ