Could Proportioning valve be the culprit? - Team Camaro Tech
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post #1 of 18 (permalink) Old Jul 11th, 10, 06:47 AM Thread Starter
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Ken
 
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Could Proportioning valve be the culprit?

The other thread was getting kind of long so I'll switch gears: Does anyone know if you can "recenter" the proportioning valve in a 69 Camaro with power front disks/rear drums, and how to do it?
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post #2 of 18 (permalink) Old Jul 11th, 10, 07:37 AM
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Scott
 
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Re: Could Proportioning valve be the culprit?

I believe you are referring to the distribution block. After the system is set up and bled, stomping the pedal will re-center it. The proportioning valve is mounted on the subframe, if so equipped. The distribution block has no valving in it, it only activates the differential pressure warning switch, illuminating the dash brake light .
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post #3 of 18 (permalink) Old Jul 11th, 10, 01:50 PM Thread Starter
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Re: Could Proportioning valve be the culprit?

I have learned to respect your advice Sauron but the part I am looking at on my car is the same one listed in Rick's catalog and called a Proportioning Valve, hence my confusion. I was told, PVs usually have a reset button somewhere on them, and mine (and the one in Rick's) appears to have some sort of button covered by a rubber boot on the back side. I haven't pressed it or tried to do anything to the brakes yet because I was told the reset procedure varies car to car. My issue is that the pedal will not go to the floor when bleeding the rears, only on the fronts. I was thinking that my attempt to pedal-bleed the empty rear lines and wheel cylinders might have tripped the Valve into partially shutting down the rear circuit.
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post #4 of 18 (permalink) Old Jul 11th, 10, 02:19 PM
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Re: Could Proportioning valve be the culprit?

I think you have to hold the button in while bleeding.
I have bleed the brakes before without doing it, but give it a try.
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post #5 of 18 (permalink) Old Jul 11th, 10, 02:23 PM Thread Starter
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Ken
 
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Re: Could Proportioning valve be the culprit?

PS: Here's the part I am referring to: http://www.rickscamaros.com/camaro-p...1967-1969.html
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post #6 of 18 (permalink) Old Jul 11th, 10, 03:35 PM
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Re: Could Proportioning valve be the culprit?

That is the "metering" or "hold off" valve. It's pupose is to delay hydraulic pressure to the front brakes until a certain pressure is achieved in the system. The button on the back side of the valve needs to be held in if you're bleeding the front brakes with a vacuum or some pressure bleeders. Pumping the brake pedal to bleed creates enough pressure to bypass it. http://www.pozziracing.com/prop_valve_info.htm


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post #7 of 18 (permalink) Old Jul 11th, 10, 03:36 PM
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Re: Could Proportioning valve be the culprit?

That part is not a proportioning valve. It holds back pressure going to the front brakes until aprox 40 psi is reached, allowing the rear drums to overcome return spring tension so the rears start working when the front discs do. The button allows fluid to pass at lower psi when pressure bleeding. It goes in the front brake line, thus it could never do anything to reduce rear line pressure.

Any proportioning valve from the factory would be in the rear brake line, and it would be mounted on the outside of the frame rail aprox under the drivers seat area.

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Last edited by davidpozzi; Jul 12th, 10 at 11:30 AM.
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post #8 of 18 (permalink) Old Jul 11th, 10, 03:39 PM
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Re: Could Proportioning valve be the culprit?

The vendors don't call the components by the correct names. That's a metering/hold off valve. It doesn't allow fluid pressure to the front discs until there is 30-40 psi in the line, eliminating nose dive. Pedal bleeding will produce enough pressure so you don't have to depress the button on the back. I just did mine both the old fashioned way, and again after acquiring a power bleeder to do it solo. It bled fine using both methods. Now if for some odd reason the proportioning valve is hanging up, it may cause rear brake bleeding problems. I do not have one in my system. The gentleman in the following thread did. I sent him over from Team Chevelle. He was having rear problems and was also mislead in terminology. I don't know if this is your problem source but it was his. The status of your rear brakes is what? Always air? Poor fluid passage? Poor pedal and inadequate braking?
http://camaros.org/forum/index.php?topic=5952.0

EDIT: Sorry Dave, this site does not tell you someone else was posting while you are typing. CRG does.

Last edited by Sauron67MM; Jul 11th, 10 at 04:14 PM. Reason: sp.
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post #9 of 18 (permalink) Old Jul 11th, 10, 04:04 PM Thread Starter
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Re: Could Proportioning valve be the culprit?

Thanks, you guys are great. The problem is after replacing all those parts, starting with empty rear lines and empty new wheel cylinders, the pedal won't go to the floor when bleeding. I was getting some fluid movement thru the hose but not enough pressure to move the shoes. After several more bleeds (and taking the springs off the rear shoes) I did get shoe movement, and also got movement after I reinstalled the springs. But still the pedal only goes down half way when I open the bleeder screws on the rears. On the fronts the pedal goes all the way to the floor like it's supposed to. So I don't know if I just need to keep on bleeding it or if something else is screwy.
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post #10 of 18 (permalink) Old Jul 11th, 10, 04:16 PM
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Re: Could Proportioning valve be the culprit?

Have you replaced the axle drop flex line? They have been known to separate internally, with fluid being forced to the outside of the inner passage which clamps it off.


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post #11 of 18 (permalink) Old Jul 11th, 10, 04:58 PM
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Re: Could Proportioning valve be the culprit?

dont buy from ricks. waay overpriced here is a great site for all types of OEM brake parts
http://inlinetube.com/

good luck
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post #12 of 18 (permalink) Old Jul 11th, 10, 05:19 PM
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Re: Could Proportioning valve be the culprit?

Quote:
Originally Posted by BPOS View Post
Have you replaced the axle drop flex line? They have been known to separate internally, with fluid being forced to the outside of the inner passage which clamps it off.
This common failure came up in another thread. I may be incorrect in my assumption that he has replaced everything new but these. After replacing with all new components it would be unwise to leave these ignored. And for what it's worth, those replacement hold-off valves, although not affecting this problem, have been know to be flawed when new. This has been discussed at CRG numerous times.
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post #13 of 18 (permalink) Old Jul 11th, 10, 10:45 PM Thread Starter
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Re: Could Proportioning valve be the culprit?

Thanks guys. I did install the two steel brake lines on the rear axle but not the flex line (along with the new wheel cylinders and M/C). Everything else, including the hold off valve and flex line are Original. But the flex line looks fine and doesn't leak. To my shame I ignored several guys' advice to replace it anyway. (Every time I replace one part I end up needing to replace two more. I was trying to limit my work—if possible.)

Are you suggesting that the originals separate or the replacements separate? I haven't had to bleed these in 25 years so I am not sure what their condition is. (Obviously I didn't drive it much.) Is there a way to test it to know for sure?
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post #14 of 18 (permalink) Old Jul 12th, 10, 04:54 AM
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Re: Could Proportioning valve be the culprit?

Looking fine does not matter. Flex lines are often a source of trouble as in the case in this thread: https://www.camaros.net/forums/showthread.php?t=182042. I suggest changing the fronts as well. They are at least 25 years old according to your statement. Origionals and replacements will fail due to deterioration. They are inexpensive and available at your parts store.
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post #15 of 18 (permalink) Old Jul 12th, 10, 06:43 AM
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Re: Could Proportioning valve be the culprit?

Quote:
Originally Posted by KenFro View Post
(Every time I replace one part I end up needing to replace two more. I was trying to limit my work—if possible.)
That is the way of these old cars. It is sometimes easier to just shotgun replace everything at once (especially brakes) than trying to fight these parts. Usually these parts are half damaged once you put a wrench on them and apply pressure.

The flex line with T block is about $30, I just replaced everything from the T block back. I had a leaking solid brake line on the axle, but the brake line had fused to the T block, no way would it budge hence a new T block. So as stated I just rebuilt everything-SS lines, cylinders, shoes, hardware. It is cheap and easy.

I don't know how you are bleeding brakes, but here is what I use.
Harbor Freight #92474 vacuum pump. It will displace all old fluid (and air)in your line in seconds, as long as you keep the MC topped off.
For such a cheap price of $25 (on sale) I have lost count of how many cars and motorcycles I've done. Actually I think I only paid $15 for mine.

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