I have been working on my new to me 75 F500 tow-truck. All was going well until the hydro-vac system took a dump. We replaced all four rear wheel cylinders and lines , new master cylinder and booster for newer heavy truck. Still no luck .
Vaccume bled the whole system three times and got pedal for about five minuets then nothing again.
We have two contracts waiting on this rig and loosing hope for hydraulic system .thinking of switching rear end out for a two speed with air brakes???
1975 F500/700 parts 361 v8 ,4 speed tranny ,rockwell single speed rear.
Any help would be greatly appreciated.
Thank you !

 

Did you check the slave on the booster? Whats the problem? pedal fades? Actually no brakes? Are you loosing fluid?

 

Thank you for the reply...It has some pedal at first then to floor .Front brakes would lock down even with pedal on floor but nothing from the rear shoes. A person here in my home town said maybe switch rear line to back of master and front lines to front of master to see if it would get more pressure. Still no go. If I start the truck the pedal gets to the floor faster but still has no stopping power. I have redone many hydraulic brakes ,air brakes and even a few electric brakes and never had one kick my butt this bad before. No fluid loss at any point.

 

we always had that problem and had to pump brake fluid from the rear drum up to the master cylinder to get all the air out , then had to make sure the brake shoes were adjusted properly !