Proportioning Valve Keeps Tripping?

[KyleSeal]

Originally Posted by RichardJ

post #34

>>My only conclusion from all of the above postings is that the Primary Section of the MC has failed.<<

I am in this camp as well.

Originally Posted by MikeB

Do you have the tools, brake line, and fittings to bypass the combo valve? It may possible that the proportioning valve is limiting pressure to the rear WAY before it's supposed to.

Then again it might be a bad M/C like Richard says. Bypassing the combo valve will tell you where the problem is, or isn't.

So I dont have the tools handy - nor do I trust my flaring abilities at this time, so I swapped prop valves. No more brake light at all, but pedal only stops the rear tires at the bottom of the pedal (on jacks, no load)

Originally Posted by Rust_never_sleeps

On old earth moving equipment, they'd sometimes use an oil can clamped to a hose to bleed hydraulic systems from the lowest point back to the reservoir.
You might try this with a big syringe from the farthest wheel cylinder. Looking for flow, and maybe trapped air. This way is messy, so rig up a drip pan and wash off any spilled fluid in the engine compartment

Otherwise, I agree with the above and you'll have to get clever with swapping parts or plumbing to isolate the problem

I have tried this as well, at this point I am convinced I have no more air (I ran two gallons through the system, last 1.5 gallon had no air)