I have a 2000 F350 crew cab dually V10, and recently had a close call when the brake pedal went to the floor.

First, a little background. The ABS warning light came on several months ago. A mechanic friend put a scanner on it, told me that the right front and rear-end ABS sensors were not reading, but that the brakes were fine -- I just wouldn't have ABS. A couple of times, when getting in it after it had been sitting in the rain, the ABS would try to engage the first time I applied the brakes, but it never failed to stop, and that behavior disappeared shortly thereafter.

Several months later, after getting it back from an inspection, I happened to look down at the dash in time to see the ABS light go out (it had never gone out in the previous several months). A couple of miles later, when I went to apply the brakes, the pedal went straight to the floor. I tried pumping it a couple of times with no effect. Fortunately, I was able to pull off the road and coast to a stop in an open field.

When the wrecker showed up, I started the struck, and the brakes were working fine at that point. I had it towed to another local mechanic who went through it, and couldn't find any problems other than the two ABS sensors. He could not reproduce the failure, replaced the rear sensor, and declared it fixed.

My problem now is that I don't trust it. I've driven it a little, and the brakes seem fine; but I have a hard time accepting that the ABS sensors caused the problem when they had been out for months.

I'd appreciate any input on whether the ABS sensors could cause the brakes to fail completely, or, if not, where else I should be looking.

Thanks in advance.

 

Bump for the day crew

 

My guess based on your description is the master cylinder.

Typical pedal to the floor scenario would be a brake line failure due to rust through. On a 2000 model in the northeast, the line between the fuel tank and frame is the first one to rust through. Pumping the pedal gives you some brake back due to the front getting 80% of the pressure but the pedal would continue to move to the floor.
But this was not your case due to no fluid loss.

I also agree an ABS sensor failing would not cause your problem.
IMO I would go after the Master cylinder. If the seals are shot the fluid can leak by and the pedal will go to the floor without external fluid leakage.

 

Thanks, gentlemen.