Here is the story, on my 1990 f-350, when the motor is off I can get a hard brake pedal but as soon as I start the truck up the pedal get real soft and almost goes to the floor. The brakes will not start to catch untill almost to the floor. It's kind of scary, so here's what I want to do. I want to bypass all of the abs if I can and I was wondering if I could just run a brake line from the master cylinder to the rear brakes, bypassing all of the abs valves. Or if any one has any other ideas I'm all ears because I'm stumped on this one.

Thanks alot

Ken

 

did you try bleeding the brakes yet?

 

yes i did all of that, I must have bled gallons through the system, all to no avail.

 

I just fixed that problem on my 79 150.I had replaced the whole front and rear brakes every part there was,new master,and some lines.After I was finished I had the same problem you have.Turned out my booster was bad.I suggest checking your vac. line and booster.After I did this my brakes worked like a new ride.Do you hear a swooosh sound threw your peddle?Ohh, and I also had presure until I fired her up.

 

Hey Guys,
I have been having the same problem on my truck. How do you check to see it the Booster is the problem?
Matt

 

I am currentling having that "swooshing" noise coming from the pedal on my '88 Bronco. While my brake problem isn't nearly as severe as the one described here, my brakes dont grab as quickly as they should. Should I be checking my booster as well?

 

My son fordbeast_80 has a bad booster on his '70 F250. Soft brakes, vacuum leaking noise and rough idle. Pulled the line and plugged it. Cured the rough idle, now he needs a booster.
Soft pedal can also be from rear brakes not adjusted up close to the drum which will result in long pedal travel. Also a weak master cylinder will cause the same thing. If your master cylinder has been on the truck for along time and you push it to the floor several times this will take out the piston seal.

 

I do not know how to check? I just bought