ok i have a 99 4x4. i recently changed the rotors, brakes, master cylinder, and all the brake lines because they kept leakin on me. OK here is my problem still, after all this my brake pedal is still spongy and if i hold hard pressure on the brake pedal like at a stop light, it goes all the way to the floor. I have bled the lines several times, and i also took my truck to a shop and he has bled them several times, and we get NO air out of them, we get solid fluid. When i push hard on the brake pedal the truck nose dives hard so the brakes are working good, but i dont think my pedal should be so soft and spongy and go all the way to the floor. The mechanic that has been helping me with my truck says that, that is how it is supposed to be with 4 wheel disc brakes, any truck if u hold steady, hard pressure the pedal will go to the floor. I disagree, it was never like that before !! Also i callled the local Ford dealer and he says that he thinks without looking at it that the power booster is bad ??? i dont know anything about them . My mechanic says that if the power booster was bad that my brake pedal would be hard and the truck would not stop well, it would be like driving a old truck without power brakes, which makes sence, but i dont know. So i am stumped, any help would be greatly appreciated. Also someone has mentioned the vacuum line could be leakin that goes to the power booster ??? OH , and there are NO leaks!!! thank you

 

ok i just talked to another ford dealer, he says that its probably my hydraulic ABS pump, and that when i changed my brakes and compressed the calibers , that could push any junk that is in the brake lines into the ABS pump and mess it up?? does anyone have any more info. on these ??? he also says that its definitly not the power booster, because if it was bad, the pedal would be really hard just like i had no power brakes at all.

 

two words, master cylinder.

 

I agree...

 

changed the master cylinder yesterday, bench bled it and bled the entire system again. thats what i thought too

 

and its brand new, not rebuilt

 

That's exactly what happened. I have had several DIYers bring in their vehicles (not just Fords either) after doing brakes themselves with this problem. Unfortunately, I don't know of an easy way to fix it. My truck developed this condition after cooking the brakes at Heartland Park a few years ago and I'm just now getting the pedal feel back where it should be. (that's not as bad as it sounds, I've only put about 4k miles on it since then). Some scanners will be able to do the factory electronic bleed that might help. Doing a pressure fluid flush might also fix it. Once the ABS unit goes haywire it is no cake walk getting it back to normal.