Brake pedal goes to the floor I cannot get any brakes to work

MIKE MCGEE

MEMBER
2007 FORD E-SERIES VAN
6.8L
V10
2WD
AUTOMATIC
150,000 MILES

I am working on the truck listed above E450 Superduty and I cannot get any brakes to work. I have replaced the master cylinder twice and the hydro boost twice (the first replacement was leaking at the brake pedal). The front calipers, pads and lines have been replaced to stop brake grabbing. Checked the rear calipers and pads all looked good. I have bled the system several times and I still cannot get a solid brake pedal. When I replaced the booster and master cylinder the first time I was able to get brake pressure but the vehicle came back with a spongy pedal. When I was moving the van to park it the brakes went out all together. I have since replaced the booster and master cylinder for the second time and cannot get any pedal pressure to bleed the system.

1 Reply

MOTOR MASTER

MECHANIC
279 POSTS

Hello my name is Dave.

An issue I have encountered with the E series super duty trucks is a bad flex hose going to the rear axle and the only way I found it the first time was to have someone else pump the brakes and as I was watching the hose swelled up with a big bubble that went back down rather quickly. I have found the same problem 2 more times since. First though I would make sure you have good pressure off the master cylinder to make sure it is primed working properly. I would do this by loosening the lines at the master and having an assistant hit the brakes, using a lot of rags to prevent fluid from getting everywhere. Provided you have a good master and have no leaks this is one of the few things that could keep you from having enough pressure at the bleeders to bleed the system however I still suspect that there is an issue with the master cylinder because it would be unusual for the hose to allow no pressure to the bleeders without leaking externally, the swelling of the hose is an internal leak in the hose where the inner layer fails but the outer layer holds the fluid but not the pressure so it expands causing the bubble and when you let it rest without pressure on the pedal the fluid bleeds back into the rupture in the pressure hose allowing it to go down and the fluid to return to the system. It's been my experience that when one fails causing a persistently soft pedal that when it looses pedal completely you will be able to see the leak. The booster failing will usually cause a hard peddle, in rare instances a overly soft or even sticking pedal but can not cause actual brake failure since there is a direct connection between the pedal and the master cylinder, the booster only effects the resistance of the movement. I hope this helps you track down the problem and thank you for using 2CarPros!