It is super cold here in NY, I figured it would be a warmer diagnosis to sit and ask if anyone has had this problem, or a solution. I took my kids to school and on the way home my pedal went down to the floor. The ABS and BRAKE lights lit up, but I was still able to stop and make it home. I checked behind me as I was driving and I see no fluid. I also have lots of snow in my drive and still see nothing. The master cylinder was empty in the front (smaller) reservoir, but not in the rear (larger). I ask for any help with great thanks...stay warm.

 

Sounds like the rear brakes went .
Could be a brake line running along frame on drivers side, from the proportioning valve to the rear brake hose.
It could be the rear brake hose or one of the rear wheel cylinders.
It could be mater cylinder, but i really really doubt it. I would check that last.
It could also be the line running from the master cylinder to the proportioning valve.
If there's no fluid on the ground i would check the line along the frame first.
Fill the master cylinder back up and crawl under the truck from the rear abd have someone press on the brake peddle.
No need to have the truck running.

Dave

 

+1 - usually the rear metal brake line running along the frame rail near the rear of the gas tank. They are famous for rusting out in that area.

 

I replaced the frame line about a year ago. I saw the old one still there so I know they must be a problem. I went out and checked and saw that one tire was "wet" looking, shiny. I guess I am changing a wheel cylinder soon...better than having to do the master or booster...Thanks again and happy trucking.