Problem with Prop Valve/Metering Block

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71Demon340

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Running rebuilt power booster/mast cyl with single piston discs and 10" drums, all new lines, and original brass prop valve/block. When I bleed the brakes, the front does fine, but don't get anything out the back. I loosen the fitting on the rear outlet of the prop valve, and its bone dry, so I am not getting anything across it. I disassembled the prop valve and cleaned it real good. All the springs and seals and such look fine, actually look brand new. Any ideas? Any chance, I assembled something wrong? Seems like it can only go together one way. I would appreciate any advice. Thanks.
 
A factory service manual will show a cross sectional view and the inside working of those valves but.. their text reads " Not servicable " That means dont attempt to repair it or call around seeking a rebuilt one. Replace it.
 
Could it be a bad mast cyl and not the valve? Doesn't seem likely, since the fronts seem to be working OK.
 
I suppose it could be the master cylinder. A pressure gauge would answer that one.
 
its the metering valve, which you should replace...the stock metering valves are extremely sensitive and the pilot will stick in them depending on where its located. Be sure to let all four wheel cylinders gravity bleed before you manually bleed your brakes and you should be fine!
 
I had the same problem with my 72 duster. There's a removable cap. Take it off and pull out the valve inside. Clean everything up really good and reinstall. That's all it took for me. I used a miti-vac to bleed my brakes.
 
I have the same exact problem no fluid out the back and brakes up front. I replaced all line master,wheel cylinders and all new lines including hard lines. I also replaced prop. valve and hold off valve. I was gonna try something else this weekend. I ordered all the line and vavle from Inlinetube. I called them and they faxed me the instructions on bleeding the prop. Valve so I just need to try it and see if it works.
 
I am having the same problem with my 71 Duster. I thought I just had air in the lines but I have bleed them and bleed them. If I pump the pedel once they are fine but if I let it sit then I have to hit the brake twice to get a good pedel. It is almost like I new a residual valve for the back. has anyone every had to run a residual valve on their car. I know they are made for cars that have the master munted to the frame and that doesn't apply to us. but I think it is wierd we are all having the same problem. On my car I have a adjustable prop valve and just using the old metering valve from the drums
 
Bleed them; never let the pedal go all the way to the floor.
Put pressure an the pedal with the rear bleeder open slightly (with a helper).
When the guy pushing the pedal feels a click- stop, and tighten
Then do the front. then go back to the back and bleed both. that first step centered the valve.
 
There may me a metal pin sticking out of what appears to be a nut on the prop valve. On some models you have to hold this pin out until the bleeding is done to keep the valve centered.
 
I gave up on the prop valve working. I gutted the rear part and spliced in a Wilwood 10 psi residual pressure valve after the prop valve. Thought I would try the $20 Wilwood valve before spending $90 on a new prop valve. Brakes work awesome now.
 
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