brake problem

[molinerat]

--------------------------------------------------------------------------------

I'm putting a S10 chassis under my classic truck. I'm currently working on the brakes and can't seem to get fluid to the rear brakes. I think in my parts gathering i got a master cylinder and proportioning valve and booster from an 89 S10. i have bench bled the master and get flow out of both ports on it. When I hook the lines up to the proportioning valve i get pressure to the front but nothing to the back. I've undone the lines and blew them out to make sure of no blockage. I've undid the line at the connection on the rear line at the firewall and get no fluid to the rear anywhere past the proportioning valve. I'm about to lose my mind trying to figure this out. Thanks for any help.

 

[Old Iron]

The proportioning valve is not centered and has the rear port blocked.
Loosen the line for the front brakes at the master cylinder, push the brake pedal down slowly, you'll feel the pedal get a little resistance to it, push a little harder until you feel a slight movement of the pedal, stop, hold the pedal in this position and tighten the brake line. This centers the proportioning valve.
Let off the pedal and it's set.
When bleeding this type of system never push the pedal all the way to the floor.

 

[sneakysnake]

Another thing is to make sure pedal and MS plunger is returning to full back position. If stroke is to short it wont let fluid into line.