Brake pedal goes to floor

[skynyrd7569]

2001 Ford Sport Trac, 47000 miles, 4wd. Replaced master cylinder, pads, rotors and calipers. With the engine running the brake pedal will not pump up.
There are no warning lights. The pedal will pump up without the engine running, but will not stay pumped up. Is there a way I can check the abs, to see if it is working correctly? How do I get the pedal to pump up up?

[shorod]

What do you mean by "will not pump up" with the engine running? You have power brakes so it shouldn't "pump up" when the engine is running. You should have consistent brake pedal feel, and it won't be as firm as when pumped up with the engine off. Do the brakes work well or are you trying to locate a problem? Did you bench bleed the master cylinder before installing it and/or bleed the brakes afterwards?

-Rod

[skynyrd7569]

Thanks for the reply. I can pump up the pedal without the engine running, but it won't hold firm. With the engine running it goes to the floor and never reaches a normal pedal height. Yes, I bench bled the master cylinder. I also bled all four wheels. I cannot drive the car as I have no brakes. I am asking what can I do, other than take it to my dealer.

[shorod]

So is this the reason you changed the master cylinder, or did this problem start after you did the work? I would suspect you still have air in the system.

-Rod

[skynyrd7569]

The reason I replaced all of the front brake parts, is that It was wearing front pads out way too fast. I really suspected the master cylinder was causing the problem. (causing the front brakes to work and not the rear brakes) The brake pedal went to the floor prior to my work. If it still has air in the system, how do I get it out? Thanks

[Davescort97]

Bleed the brakes again starting at the farthermost wheel in relation to the master cylinder....should be the RR wheel, the LR wheel, RF wheel, LF wheel. Have the motor running while you do this. I seriously doubt you can get all the air out of the system without the brake boost operating.

[skynyrd7569]

Thanks I will give it a try

[shorod]

I'd be inclined to suspect that the front pads wearing out too fast would be due to either a collapsed brake hose or a sticking caliper, assuming the inner and outer pads were wearing evenly. If one pad is wearing faster than the other on each side that would suggest a brake caliper slide pin issue.

As for the pedal going to the floor, that often would indicate a master cylinder issue if there wasn't a way for air to enter the system recently.

For flushing/bleeding brake systems I find myself reaching for this tool. I have a MityVac and have not been as successful getting air out of the system as when using this tool, plus my hand appreciates not having to constantly pump the vacuum pump. I picked it up when it was on sale for $19 and it's definitely already paid for itself.

-Rod

[skynyrd7569]

thanks for the info

Tony

[inafogg]

i'd rec you bleed the master cyl 1st if you have'nt(i know you bench bleed)
some times air is trapped.i would think your ok at the pump unless you had it
opened