driving the truck home the other day and i lost my brakes. you can push the pedal and it will start to brake but then the pedal will fade to the floor and you have no brakes at all then you have to start pumping the pedal. the only place it is leaking is from the left rear drum. the drum itself is soaked in fluid making me think that the brake cylinder went bad. but would that cause a total loss of brakes? i popped the cap on the master cylinder and the front resivour was empty all for about 1/16 inch of fluid and the back was about half empty. both were low enough that it had sucked the caps on the lid down in to the resivour. everything makes me think that it is the rear cylinder leaking except the fact that when you have the truck off you can push the pedal to the floor (obviously with no assistance from the booster) and that makes me think that it could be a master cylinder problem. any assistance would be greatly appreciated. trying to stop a 1984 tank with no brakes isnt easy!

 

same thing happened to me..... there is a way to keep that from happining, you can put in a brake proportioning valve .... mine was real small and it just limited the flow no pressure to the rear brakes.... I had to remove mine and months later someone pulled out infront of me and I had to slam on the breaks....POW... blew the rear wheel seal on the rear passengerside... ended up hitting the guy anyways..just not as fast....

go to local parts store and tell them you want a proportining valve from an 87 f-250... that will solve that issue ..... not sure if any other years have this same devise but it works ..... put a new one in and now all is good...

 

if you re-bleed the system and have no brakes adjust the drum brakes on the rear. i had the same problem with the dana 70 out of a 1990 thats under my 79. the adjusters were also froze up, you can get a kit with new adjusters from orielies for like 15 bucks...hope this might help ya

 

The front of the master cylinder being empty will cause the no brakes. When you push your brake peddle the top of the brake peddle travel is the rear brakes which comes off of the front of the master cylinder (the reservoir closest to the firewall) , the bottom half the the travel is the front brakes (the reservoir farthest from the firewall) . You want the rear to start working first so you still have steering control when braking. If the front of the master is empty your brake peddle will be soft. You can get a proportioning valve for a 94 F350 from your local parts store. They screw right into the master cylinder on the rear brake reservoir then your brake line screws back into it. The older fords that did not come with the proportioning valve have a problem with over pressuring the rear wheel cylinders and blowing the seals out, so if you don't add the proportioning valve it will just keep doing it. As to being able to push the peddle to the floor with the truck off its because there is no fluid in the brake lines to compress. Your brakes are nothing but a hydraulic system, when the system is full you have to compress the fluid which creates resistance making it hard to push. With no fluid in the system there's no resistance so its easy to push.

 

Those master cylinders have a reputation as well for blowing internal seals if you put them to the floor. While the cylinder may have caused the loss of brakes, be prepared for the possibility that you may have to replace your master cylinder as well.