How to reset the valve in the Brake Combination Valve? - Chevy Nova Forum
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Old 25th-November-2009, 09:31 PM   #1
siderman

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How to reset the valve in the Brake Combination Valve?

Everything in my brake system is new. I bench bled the master cylinder and plumbed everything up. I didn't gravity bleed the brakes like I was told to do. I just started at the passenger rear with a homemade brake bleeder (bottle of fluid to keep air out). Wasn't long till I got no fluid out of either rear brake cylinder. I hooked up the light and it stays on. I figure the cylinder in the valve shifted and cut off flow to the rear.

How do I reset it? I tried googling it and I read you can loosen the front bleeders and pump the brakes. Others said this wouldn't work and that you had to pressurize the rear with a pump or air pressure to push it back. Looking at diagrams of these valves, it looks like if it kicks out with a front leak that a thing pops out in which you can push back to reset it, but I see nothing for the rear. I can't see how opening the front side will reset it because their is no way to get pressure behind it to push it back.

In my research, I read about the tool that replaces the switch to hold the valve in place for bleeding. Anybody ever make one? Can you buy one at an Advance or Autozone? Thanks.
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Old 26th-November-2009, 06:01 PM   #2
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you will have to center the valve first anyway before you install the
valve centering plug.
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Old 26th-November-2009, 06:04 PM   #3
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oh , i fogot, go to cpp brakes site and go to their troubleshooting guide ,
it expains how to center the valve.

i know ,cuz i just did mine , what a pain , get the tool (plug) next time.
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Old 27th-November-2009, 12:57 AM   #4
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Thanks for the link. I copied the part from the article below. But the link to the whole article is http://www.classicperform.com/TechBo...t.htm#testprop It seems very good and covers alot of brake problems. I hope it works.

Test Combination/Proportioning Valve
Use a test light by attaching a clip to a positive contact on the vehicle and touch the point of the tester to the electrical connection of the combination valve. If the the light does not come on, the valve system is operating correctly and no further testing is required.
If the light does come on, this indicates that the pressure differential valve is stuck in the front or rear position.
Bleed the brake system to determine if the front or rear lines are blocked off. Set up one front wheel and one rear wheel for bleeding at the same time. Crack both bleeder screws and gently pump the pedal a few times.
The blocked side will trickle fluid out when the bleeder screw is cracked and the pedal pressed. An unblocked line will squirt fluid out the bleeder.
The lines that are clear must be left open and the blocked lines should have the bleeder screws tight to cause pressure to build up on that side. Be sure to use the standard bleeding procedures to prevent air from entering the system.
Slowly press the pedal with steady pressure a number of times until the light goes out; this will center the differential valve. You may also hear a pop come from the proportioning valve. This is the metering valve returning to its equalized position. When the light goes out, close the bleeder screw. (See fig. below)
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Old 30th-November-2009, 11:39 AM   #5
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Closing the bleed screws on the shut off side and opening one on the side that worked (front for me), did the job. Valve centered right up. Would like to get one of those tools though, although since in the drawings this is open to fluid, I can't see how you would remove and reinstall the switch with the breaks blead without inducing air back in the system?
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Old 30th-November-2009, 07:27 PM   #6
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i didnt really look at it , but i would think you would have to re-bleed anyway.
the tool is used so you dont shift the valve.
if your carful ( say put a 2x4 under your brake pedal, to keep from over
stroking ) you could get buy without the tool assist.

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Old 24th-February-2011, 01:14 PM   #7
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whats the average time frame it takes to center up the valve this way. Or how long or how many pumps of the brake pedal did it take to center the valve?
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