70's fseries brake problem

[DeepRoots]

no fluid flow to rear brakes.
this would be a 76, without power brakes, front discs (which work great) and rear drums.
Can't even really bleed the rear drums. no leaks are visible.

I'm assuming it is the proportioning valve. Pulled the piston out on said valve and met with limited success....

any way to fix/service/get working this valve?

Thanks,
Drew

 

[towcat]

drew-
time for a new(newer or newused) proportioning valve.
blow out rear line first tho. might be something as simple as a bad rear hose.
ya never know.

 

[DeepRoots]

I was hoping you'd come in on this one.

I was afraid this woulda been the problem. New proportioning valve is like $300.... screw that. Summit has adjustable ones for $50 a pop.
Might hit the junkyards in the morning and see what I can dig up first.
In the meantime, since I'm sitting in the shop drinking beer and I'm bored, I'll take the whole system apart and clean everything.

thanks
Drew

 

[DeepRoots]

on another note, it sucks to have the tow pig once again running great for no apparent reason, and the REALLY fun zoom zoom truck down in the shop.

 

[towcat]

drew-
these trucks are still all over the place out here.
if you want to try a newused unit, I can hit the wrecking yard over the weekend. need to know if you are disc brake front or drum front?

 

[DeepRoots]

disc.
I got it tho.
I took the valve apart (bout 35 pieces) and it was all gunked up. I'm soaking the main body in carb cleaner and will blow it out in the morn.
course while disconnected I tested the master, it's only putting out in one section, so I'll take it apart and figure it out in the morning or find a new one.

damn I hate when a truck sits for like 5-6 years.
still, I love these old trucks, the parts are a quarter of the price vs our beloved diesels.