ok here goes, I replace the rear shoes and wheel cylinders (cylinders bad ruined shoes), master cylinder replaced because it wouldn't keep pressure, left front caliper replaced (frozen), both front rubber lines replace, rear rubber line replace (lines original) and front pads replace with rotors turned (replaced 12-07). I have bled the lines no bubbles any where pedal gets firm with engine off. I've gone through almost 3 qts of brake fluid also so I would flush the system out also. When I start truck to check pedal it is soft and goes to floor slowly. What is going on here. I am stuck on this one. Please shoot me some ideas.

 

Did you bench bleed the master cylinder before it was installed? If not, you may have air trapped in it. Could be a bad master cylinder right out of the box,...reman or new.

 

Going to the floor slowly is normal for these trucks. There is an updated vacuum booster to correct. If the pedal is soft to start with but will pump up you either have air or the rear brakes are out of adjustment.

 

First one was a reman and it was bad, then bucked up and bought a new one and bench bled it. I think I finally found the problem other than the rear brakes not being adjusted out enough. the NEW wheel cylinder I bought is bad I found a small a very small amount of fluid leaking at where the line connects to the wheel cylinder. I will let you know on my progress. Been having to work alot lately (on call) so working on truck in between.

 

ok now that the hard line and wheel cylinder have been replaced still have soft pedal when engine is started. I gravity bled the lines then pump bled the lines (went thru 1QT of fluid). I started the truck and pulled the vacuum line off of the booster and I had a hard pedal like suppose to have, and did not go to floor. Put it back in and waited a bit for vacuum to build and pedal went to floor again. GRRRRR. What in the #%^^ is wrong with my brake system? Is my brake booster bad? I'm lost on this one.

 

I have not had many problems with our brake system yet but some have. Some have had your same problem. I believe they replaced just about everything. For some reason the booster and master cylinder come to mind.Heck you can even do a hydro boost. That probably would fix most of your problems.

 

I found that I keep blowing out the master cylinders. They keep leaking at the booster. What causes that to happen? I have put on an Orielys, napa and auto zone master cylinder on. I guess I will try a Ford one I don't know what else to do.

 

I GOT IT FIXED!!!!!!!! After replacing the master cylinder, the proportioning valve, the RABS (the rear antilock braking system that is below the master cylinder on the frame) the pads, rear wheel cylinders, rear shoes, all rubber hoses (all were original), driver's side caliper, and of course fluid (6QTS later after bleeding and rebleeding) still had a soft pedal. Ford stealership even loaned me their repair manual to fix this thing, this step was not in their book at least not where I could find. They also didn't mention this, I asked if there was any special steps I was missing. I had a buddy who works for a Honda dealership call one of his mechanic buddies and he told me to go and drive it and make the abs system activate at least 3 times. Then go rebleed the system one more time and then I should have brakes. Guess what he was right. I have the best brakes that the truck has ever had!

 

I don't remember if the brakes were soft ever since I got the truck. A little over a year ago, I was driving up to my mom's house and the brake line going to the rear wheels blew. Luckily, there was no one around me and I was able to pull off into a gravel parking lot. I was close enough to make it to my mom's, but I was 1.5 hours from my house. Also, I was in a town that rolls the sidewalks up at 5 on the weekdays and earlier on the weekend (it was a weekend). Luckily, the only auto parts store in town was open had some replacement lines. So my dad and I got a length and replaced about 4 feet of rusted lines. Since then I have also replaced both front calipers and pads. I have not done anything with the rear brakes themselves.
Definitely since those two instances, my brakes have not been that great and they are doing the exact same thing as yours were doing. I've tried re-bleeding my brakes at least three times so far. I cannot get my RL wheel cylinder bleeder to open, so I dumbly and impatiently just skipped that one in my bleeding process. I think I might just replace that one. So that long story is a build up to my one question... (Done rambling )

How do you get the RABS to activate?

 

it should do a self check once an igntion cycle. drive it then shut it off, drive agian then shut it off and then drive one last time and shuting it off

 

I believe you have to do a driving test with that one. I forgot where I read that or was told that. You have to get up to 30-35 mph and slam on the brakes and do that twice after you have bled the entire system. If you have not bled the LR I can almost bet you have air in your system. I did. It took me FOREVER to get the air out of my system.

 

Can anyone please help? I have been reading the posts and it seems like I have the same trouble that someone else had. There were a lot of answers to his problem though, so I don't know what worked. I have a 94.5 Dually, 4x4, with the 'F' engine code (early powerstroke). My pedal goes to the floor as soon as the truck is started. You can try to pump up the pedal and when you do the brakes are great but it will just sink back to the floor. I have changed the vacuum pump, the vacuum booster, the master cylinder (4 times) the brakes, rotors, wheel cylinders and even the adaptor that threads into the rear port of the master. It has been bled by myself and 3 different garages (where 3 of the masters were also changed) and there is NO air in the lines. It will pump up and hold a pedal if the truck is off and if I disconnect the vacuum from the booster the pedal will get hard and stay hard. If I put on the emergency brake, it will nearly stall the truck (standard) trying to take off. I currently have a Ford master cylinder on it. Yes, I bench bled it before putting it on, as I did with the previous one and the garages did with the other three previous ones. My ABS light has been on since I bought the truck back in 2000. I am supposed to make a 600 mile trip in a few days but I can't go if I can't get brakes on this old gal., Thanks to anyone who tries to help, Norma

 

Go here....Do this
https://www.ford-trucks.com/forums/6...-problems.html

Even though you replaced the booster you didn't get this booster. Its not in the regular listing at the Ford store it has to be ordered by part number

 

The 94 and 95 brake boosters were notorious for letting the pedal go to the floor even when the brakes are adjusted. You have to get the right zero loss brake booster for it. Like has already been said a couple time.
Or ask for one for a 97. That is a zero loss updated one.

There is a bleeder on the abs actuator FYI. You don't need to go out skidding your tires.

Adjust the back brakes tight. TIght enough so that the park brake pedal only goes down a couple inches and the service brake not even that with a very light drag on the drums. VERY LIGHT. Don't burn them up.

 

I asked someone earlier ab out how to fix this and found this to be a great result.
I replaced RABS valve and it fixed the problem.