I have a '98 F150 with 4WD & rear-ABS. I replaced the front calipers/brackets, pads & rotors. I had a friend help me bleed the brakes and while we were doing so the brake-line in the center of the truck blew. I replaced the line from the ABS (under the master cylinder) to the rear brake hose. Once everything was connected we attempted to bleed the brakes again. When I started the truck up the pedal went straight to the floor with no resistance. We went through two bottles of fluid bleeding the brakes again and again and there are no leaks, pedal just goes straight to the floor. Any thoughts?
Bench-bleed the old master cylinder?
Replace the mater cylinder (and bench-bleed the new one)?
Thank you to anyone who may be able to offer advice.
Ben

 

If you are confident there are no leaks.
And you did a good job bleeding it.

Then it means the MC is bad. You will need to re-bleed the entire system once you put it on (even if you do a bench bleed)

 

^^ x2

 

Thanks for the advice.
I purchased a new master cylinder, bench bled it per the instructions, installed it on the truck, rebled the entire system three times, no luck. Fluid comes out of all bleeders crystal clear and still no pedal.
In the Haynes manual and a few forums I have read that air can become trapped in the ABS block and the only way to bleed it out is by using a Specific Scan Tool.
The line that I replaced went from the ABS block to the rear brake hose... I had the line off all night so I am guessing the ABS block went dry and that air is now trapped in it.
I am having the truck towed to a local repair shop today to see if they can figure it out.

 

Perhaps use a vacuum pump brake bleed tool? You also may try to bleed them with the front jacked up, then with the back jacked up.

 

Before having the truck towed to the local-shop I tried using a one-man vacuum bleeder with no success. I had the truck towed to a local shop and it turned out that I put the brake calipers on upside-down. The bleeders were on the top and air was trapped inside.
Expensive lesson-learned!
Thanks to everyone who offered suggestions!

 

Glad you got it fixed, but I had no idea that could be done!