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I Have a 1981 Toyota pickup. "sunraider" RV. I changed the fake 5 lug axel for a 1 ton 6 lug free floating axel. My problem is the load sensing proportioning and bypass valve. I get solid brake fluid to the valve. But coming out of the valve just air and a little fluid. The back brakes don't work at all. Could that be fixed by an adjustment or is it a bad valve and I need a new one? Also what would happen if I was to bypass the valve altogether. Just a thought cause Toyota says its $270.00 for a new one. Thanks for your help.:|
 

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04.5 VW Jetta GLi
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Jegs and Summit sell an adjustable proportional valve. Worth a shot if you don't mind it being fixed in one setting.

Be sure the arm is up all the way when bleeding the rear lines.


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'84 2WD Pickup
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My problem is the load sensing proportioning and bypass valve. I get solid brake fluid to the valve. But coming out of the valve just air and a little fluid.
To take your statement at face value, sounds like you found the problem. I'm not sure where the air might be coming from though. You may have more going on than a clogged proportioning valve.

Aftermarket valves are available for under $100. Used ones are available for under $50. Or you can try to clean your one. They're pretty basic. It's probably just clogged with rust.

I'm thinking that if the proportioning valve is clogged, your rear brake lines might be clogged too. You might check that out before making a decision. Can you blow compressed air into them? Do they hold pressure? Do the rear brakes engage with air pressure on the lines? Does the air flow when you open the rear bleeder valves?

If all looks ok with the rear lines, then just clean or replace the valve and bleed the system until fluid runs clear.

As for your question, if you bypass the valve, you won't get optimum 70% front - 30% rear braking. It's ok to do as a test. In fact, it's a darn good way to test the rest of the rear braking system. But you want a proportioning valve on the road. I mean, with no rear brakes you already are operating at 70% breaking efficiency. Bypassing the valve will make matters worse.

That's my 2c. YMMV
 
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