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Discussion Starter #1
I've got a disc/disc setup in my 67 with the Right Stuff Getdiscbrakes. Since I installed it, during bleeding it only pumps out the front brakes. The rear it just trickles out. Had a couple of guys over and they say the proportioning valve is not centered and it's likely to the rear blocking off the rear flow.

I've pulled off after trying things like opening the front bleeders and putting the pedal down slowly, closing the bleeders and let pedal back up. Tried mashing the pedal real hard with front bleeders open to no avail. Did it with rear bleeders open as well and still the same.

So, I've taken the prop valve out and trying to figure out how to center this. Also, if I do succeed in centering it I guess I should be using one of those Brake Proportioning Valve Tools to screw in the brake warning light hole to pin the valve holding it in center? Here's a pic of what my setup is like.
 

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The valve is spring loaded & not the problem. The problem is the master cyl piston is not returning fully & not uncovering the replenishment port
 

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Did you bench bleed the master cylinder first? If you did not, you probably ripped the rear brake plunger.
 

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You wouldn't happen to be working on an AC car that has the brake pressure regulator valve in line to the rear brakes (located under the car about where the driver sits).
 

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Or it's the hold off valve located by the MC. It has a spring loaded plunger in it at the back with a rubber cover on it. To bleed the back brakes you have to hold the plunger down (in), otherwise just the front gets bled.
 

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Discussion Starter #6
The valve is spring loaded & not the problem. The problem is the master cyl piston is not returning fully & not uncovering the replenishment port
A brand new one from Getdiscbrakes. I bench bled the MC and pumps out of both ports. Could it be I need to have more space between the booster rod and MC?
 

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Discussion Starter #7
Did you bench bleed the master cylinder first? If you did not, you probably ripped the rear brake plunger.
I bench bled the MC and pumps out of both ports. Put on car after bench bleeding and appears to do the same when pumping the pedal. I can't say for sure but it seems the forward tank puts out a more powerful spurt. I guess I should check spacing between MC and booster rod? It came as a kit from Getdiscbrakes so I would expect a kit to be ready as far as MC and booster rod spacing is concerned.
 

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Discussion Starter #8
Or it's the hold off valve located by the MC. It has a spring loaded plunger in it at the back with a rubber cover on it. To bleed the back brakes you have to hold the plunger down (in), otherwise just the front gets bled.
Sounds like that hold off valve is a stock item? I have the new Getdiscbrakes setup so it's basically just the MC and combination/proportioning valve as seen in my pic in the original post.
 

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Your new system certainly has the "newer" combination valve like used on the second gen and later cars. This combination valve incorporates all the separate functions of the separate valves used on the first gen cars including distribution, the warning light switch, rear proportioning and the metering/hold off function. Thus, there is no separate metering or hold off valve in you system to worry about. As already mentioned, do confirm that you don't have the OEM proportioning valve that would be mounted to the subframe under the driver seat area of the car. I'd call the manufacturer and ask them some questions about the problem.
 

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Discussion Starter #10
Your new system certainly has the "newer" combination valve like used on the second gen and later cars. This combination valve incorporates all the separate functions of the separate valves used on the first gen cars including distribution, the warning light switch, rear proportioning and the metering/hold off function. Thus, there is no separate metering or hold off valve in you system to worry about. As already mentioned, do confirm that you don't have the OEM proportioning valve that would be mounted to the subframe under the driver seat area of the car. I'd call the manufacturer and ask them some questions about the problem.
Nope, I don't have the OEM proportioning valve under the subframe. I've called the manufacturer twice and they are not helpful at all. Said to take it all off and bench bleed again, then said to check and see if something's in the way going rearward, there isn't as I cracked the connection under the driver's seat frame rail and I can blow air either way front or rearward. The manufacturer, Getdiscbrakes.com has an email help portal on their web site and I've emailed them a few times and NEVER got a response. So, I'm left to my own devices now and I'm going to check by hand holding the bleeder hoses for equal pressure while the MC is in the car with someone pumping. That way I'm checking to see if the MC is too close or touching the booster pushrod. It came as a kit, of course, so it should not be awry in that area.

If both bleeder hoses are putting out equal spurts of fluid and pressure, then the problem would have to be below the MC, correct? And that would be the combo valve I would think. I've had a test light hooked up to the warning light switch and it is off most of the time when pumping the pedal.
 

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I bench bled the MC and pumps out of both ports. Put on car after bench bleeding and appears to do the same when pumping the pedal. I can't say for sure but it seems the forward tank puts out a more powerful spurt. I guess I should check spacing between MC and booster rod? It came as a kit from Getdiscbrakes so I would expect a kit to be ready as far as MC and booster rod spacing is concerned.
Check this, this is the most common issue with Camaro brakes we see here.
 

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This little dude screws into the hole where the brake warning fitting goes to keep the prop valve from accidentally getting imbalanced. Cheap insurance for the PIA of resetting it.
 

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This little dude screws into the hole where the brake warning fitting goes to keep the prop valve from accidentally getting imbalanced. Cheap insurance for the PIA of resetting it.
It's definitely at the top of my shopping list, thanks!
 

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This little dude screws into the hole where the brake warning fitting goes to keep the prop valve from accidentally getting imbalanced. Cheap insurance for the PIA of resetting it.
What is this called and where can I get it?
 

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Discussion Starter #15
Found one from Classic Performance at Summit Racing: https://www.summitracing.com/int/parts/clp-pv-tool/overview/

One would think one size would fit all proportioning valves, but must double check to see.

By the way, my valve was stuck rearward, I took my valve to a brake specialist and we used a small jewellers screw driver and pried the valve back to center. I'm beginning to think that the valve came that way to begin with, my kit was a "second" in that a few of the little bags were already opened and some hose brass/copper washers were missing. But then I had 2 sets of master cylinder to proportioning valve steel tubes.

So, what I did upon reinstall was to hook everything up to the prop valve and below. Then I attached the master cylinder to proportioning valve steel tubes and hooked up a clear plastic tubing to each steel tube, one being forward and the other being rearward. I then adapted a Motive pressure bleeder to the tubes and ran brake fluid at 10 - 12 PSI and bled fronts first and then the rears, hurray, finally get brake fluid flowing all around. Bench bled the M/C and mounted it and then did a quick swap from the clear plastic tubes to the M/C without any loss of fluid and lo and behold, they worked!

Lessons being learned I'd know how to fix this the next time a lot quicker. I won't be buying the Right Stuff "getdiscbrakes dot com" stuff again. First the valve was off rearward, and secondly I had to cut a stainless steel line at the driver's side rear axle as that was over a foot too long. You'd think when they say "fits your 67 - 69 Camaro and that it would fit right on, but then it's not a good fit.
 
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