I have disassembled and cleaned those valves. Theyre simple devices.However, that valve may not be your problem.
-Three things come to mind. A) are you sure the brake lines are plumbed correctly, and B) are you sure the master cylinder is clear of air, and C)are the calipers/pads correctly installed on known good rotors..
-The tip off is when you said that with multiple stabs, the pressure comes up.
- Now Im not going to tell you to clamp your OEM flex hoses, for diagnostic purposes. But if you did it would eliminate all mechanical problems except those pertaining to the M/C,the pushrod, and the pedal. If the problem persisted, it would point to air trapped somewhere or a faulty mastercylinder. If the problem were to cease with clamped lines, then unclamping the fronts,one at a time, would likely reveal the culprit.
-WARNING........Clamping flex-lines is highly NOT-RECOMMENDED,especially with used or old lines.While, if properly done, no damage is visible, old lines can suffer internal damage which may not manifest until many miles go by. In very hard to diagnose cases, I have successfully clamped them.Your results may vary. Your life depends on those lines not failing.
-As a parting tip,Air is fairly easy to prove. Have an assistant pump up the pedal until it is fairly hard, and hold the pedal down. Now, you, standing beside the drivers fender, lift the M/C cover, and peek under it. Then ask your assistant to remove a tiny amount of pedal pressure. You will be watching the fluid in the reservoir.If nothing is happening, reduce pedal pressure a tiny bit at a time until the fluid appears to boil. The boiling is the fluid returning to the bowl.It should be visible but modest. If you get a geyser, thats almost a sure proof that there is air in there somewhere. If the geyser escapes the bowl and spews fluid all over everything, Shazzam, thats air for sure. So the big tip here is prepare for the spewing geyser before-hand by protecting your paint. If you hold the cover just right you can prevent a mess, and if you signal your assistant to reverse directions on the pedal when the geyser begins, you can almost eliminate it.BE PREPARED. There is one caveat, If the rear shoes are out of adjustment, the shoe return springs will plow that fluid back to the M/C likety-split quick.So adjust them first.Also if the front calipers have mechanical problems on their sliders or the pads are springy, that will also cause the fluid to return faster than normal. With clamped lines all these problems are eliminated, and the only thing that can cause a geyser is compressed air in the lines. Hah!
- Oh yeah, one more thing; if the compensating port is not working there may not be any fluid motion, or barely any motion. But then the brakes wouldnt pump up at all.
-Oh yeah, one last thing; if the M/C is faulty in that the front cup is bad,there will be fluid returning to the bowl during every brake pedal down motion. You will have to watch for it because the amount of fluid bypassing is very small and sometimes hard to detect.
All right then, good hunting.
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