Proportional valve leaking - Vintage Mustang Forums
 
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post #1 of 13 (permalink) Old Yesterday, 03:23 PM Thread Starter
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Proportional valve leaking

Brake proportional valve is leaking on my 66 GT, A-code. What is everyones recommendation, rebuild the valve or replace it with an aftermarket valve. I am unable to find an OEM style replacement. Thanks for your replies and suggestions.....

George
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post #2 of 13 (permalink) Old Yesterday, 04:54 PM
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Are you sure its a proportioning valve? I also have a 66 GT, A-code, car and it only has a Kelsey Hayes residual valve and not a proportioning valve. A proportioning valve would have a minimum of three brake lines connected to it, front, rear and MC. The residual valve only has two lines, one from MC and the other to the drum brakes at the rear of the car. I'd be inclined to replace the master cylinder with a dual reservior unit, perhaps finding one with a built-in residual valve as required for drum brakes on one port. That would improve safety and eliminate the residual valve.

'66 GT Coup, restoration after 43 years in indoor storage
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post #3 of 13 (permalink) Old Yesterday, 06:41 PM
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The proportioning valve is a bit difficult to service. Kits are available but the valve itself usually will require a sleeve or honing. This is the local shop I used the last time and the price. I am sure if you look around you will find someone capable. Brian
Attached Images
File Type: jpg 65 Proportioning Valve-Distribution Block Assembly 1.JPG (286.3 KB, 5 views)
File Type: jpg 65 Proportioning Valve 1.JPG (303.8 KB, 6 views)

5R09A 4 Speed GT Built 5/29/65
9T02R 4 Speed SCJ Built 9/19/68
Owner Driver Mechanic

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post #4 of 13 (permalink) Old Yesterday, 06:49 PM
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Quote:
Originally Posted by DustyB View Post
Are you sure its a proportioning valve? I also have a 66 GT, A-code, car and it only has a Kelsey Hayes residual valve and not a proportioning valve. A proportioning valve would have a minimum of three brake lines connected to it, front, rear and MC. The residual valve only has two lines, one from MC and the other to the drum brakes at the rear of the car. I'd be inclined to replace the master cylinder with a dual reservior unit, perhaps finding one with a built-in residual valve as required for drum brakes on one port. That would improve safety and eliminate the residual valve.
There were no factory 65/66 GT's built without a proportioning valve.

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post #5 of 13 (permalink) Old Yesterday, 06:58 PM
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In a Factory 66 GT (Of course has front K/H Disc Brakes) will indeed have a Proportioning valve. This valve will be located on the drivers apron-Left of the single bowl master. It will have ONE line in from master, ONE line out to Rear Brakes.
The Apron will also have a Brass DISTRIBUTION block. It will have one line in, two lines out to Left front, Right front brakes.
As has been stated, The proportiong valves can pit badly in the bore. If pitted, they will require sleeving. If a slick clean bore, rebuild. I think NPD has a rebuild kit
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post #6 of 13 (permalink) Old Yesterday, 07:00 PM
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There are supposedly two different styles of those Kelsey Hayes proportioning valves. The
rebuild kits are different. We didn't mess with them, preferring to install a K/H dial-adjustable
valve in its place.

White Post Restorations used to rebuild these valves. (Usually they need honing, etc.)

Here's some details on what's inside those valves, etc....

http://www.stangerssite.com/brakevalve.html

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post #7 of 13 (permalink) Old Yesterday, 07:48 PM
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I was wrong in my proportioning valve vs residual pressure valve comments earlier. Proportioning could take place with just one valve spliced into the rear break line since the front discs are directly connected to the master cylinder and always receive full pressure.

'66 GT Coup, restoration after 43 years in indoor storage
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post #8 of 13 (permalink) Old Yesterday, 08:12 PM
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As GT289 stated, there are two different styles as described in the link below with very good rebuild instructions. Mark is also very helpful in the process if needed. He also custom makes one of the seals that is NOT supplied in any kits. The key as mentioned is the condition of the bore and the piston. I got lucky. Easy to rebuild.

http://www.stangerssite.com/brakevalve.html

Sorry...didn’t see that he already posted the site.

Regards,
Patrick
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post #9 of 13 (permalink) Old Yesterday, 10:58 PM Thread Starter
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Thanks everyone that has replied today to my post. The pics that Brian posted are a BIG help, as my brake system doesn't look like the pic. Seems I am missing the brass distribution block, looks like I will be ordering more parts. This explains the poor braking performance I have had since I got it running. Here is the history...., car was bought sometime in the mid 80's by my wife's brother in-law, He got sick shortly after that, and the Mustang was not a priority, so it sat in the garage. After he passed in 2003, I asked his wife about buying it, and she would not sell for what I was willing to pay. She passed in 2016 and a few months later I asked the grown children if they would sell the Mustang to me. After we agreed on a price, I was able to find someone to rebuild engine, the manual transmission, the front suspension and the brakes. Who knows what was done to the car prior to the mid 80's, so I am trying to work on what I know I can do, and what I can't do, I am having someone else work on it. I have learned so much from everyone that posts here on VMF. Thanks again.... George
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post #10 of 13 (permalink) Old Today, 06:57 AM
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For anyone who is looking to rebuild an original, I just got quotes from White Post Restorations and Jim Cowles at Shelby Parts for rebuilding and restoring my KH PV;
White Post - $150.00 plus shipping
Jim Cowles - $295.00, or he will buy yours for $100.00
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post #11 of 13 (permalink) Old Today, 08:50 AM
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You have to have SOME sort of distribution block to split the single outlet for the front brakes into left and right. Many times when the original has gone by the wayside a simple brass "tee" is used, which is perfectly acceptable as all it does is split one line into two.

On my '66, which already had an aftermarket adjustable proportioning valve (and a leaky one at that), I upgraded to a dual-circuit master cylinder (Raybestos MC36440) and a GM-style disc/drum combination valve (see photo) to make things a bit simpler. I also got a pigtail for the warning lamp switch to have a functional warning lamp.


Bart

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post #12 of 13 (permalink) Old Today, 09:52 AM
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I used the gentleman on Stanger's site.
It was $125 for the sleeving and the rebuild. I sent it out on Friday and had it back the next Friday.
Mark Frappier
82 Mountainview Drive
Agawam, MA 01001
800-528-5235
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post #13 of 13 (permalink) Old Today, 05:11 PM
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Quote:
Originally Posted by DustyB View Post
Are you sure its a proportioning valve? I also have a 66 GT, A-code, car and it only has a Kelsey Hayes residual valve and not a proportioning valve. A proportioning valve would have a minimum of three brake lines connected to it, front, rear and MC. .....".
this is not an accurate description of the '65/'66 Kelsey Hayes proportioning valve. It only has two lines. The front brake pressure is NOT part of the proportioning valve circuit. The proportioning valve just reduces pressure to the rear brakes , that's all.

OP, If originality is important then I'd have a professional re-sleeve the proportioning valve and restore it. The do it yourself kits will not address the most common issue, which is a pitted bore. Jim Cowles of Shelby parts and Restoration does them, and does a fantastic job.


Z

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