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Old 07-04-2015, 03:11 PM   #1
MattPSU
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New Proportioning Valve Leaking

I installed a new master cylinder, booster & proportioning valve a few months ago. I was able to bench bleed the master cylinder, got everything installed and bled the lines with no problem. Everything was fine for 6-8 weeks when all of a sudden, the prop valve started leaking heavily out the front and I lost 90% of my brakes. Fortunately, I was in my driveway and I was able to get the truck into the garage. Pirate Jack, the company I purchased everything through, sent me a new prop valve which I installed. Everything was OK for a couple weeks, and it starting to leak out the front again. After driving it some, I come back and the rubber boot is slowly dripping fluid.

I picked up another prop valve from another company (it looked exactly the same and the packaging was the same as well) and after a couple weeks, the same issue started. Slowly leaking out the front under the boot.

When the boot is off, and the brakes are pressed, the pin on the front of the valve pushes out and fluid leaks from there. Do I have another bad valve? Is there a pressure issue? Any suggestions on how to fix this?

Thanks in advance - Matt

Could it be a pressure
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Old 07-04-2015, 04:55 PM   #2
leftybass209
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Re: New Proportioning Valve Leaking

The problem is with the metering valve. This is a common problem with the modern brass style proportioning valves. CPP has just the metering valve which can be swapped in.

I'm currently experiencing the same problem, so I'm looking to other designs to cure the issue.

Best of luck, I know it's irritating.
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Old 07-06-2015, 05:50 PM   #3
MattPSU
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Re: New Proportioning Valve Leaking

Thanks for the input Lefty, but someone else has to have some input or a possible solution. Anyone else care to chime in?
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1972 Chevy Cheyenne SWB - Build: Porterbuilt State 1 Front & Rear, Bolt in Notch, McGaughys 2.5 Drop Spindles, Boyd Welding Fuel Tank

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Old 07-21-2015, 04:26 PM   #4
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Re: New Proportioning Valve Leaking

Pirate Jack just sent me a new piston for the inside of my prop valve. It includes the pin that comes out the front of the housing. To be honest, there's such a size difference between the OD of the pin and the ID of the hole, it's no wonder the thing leaks there. Should the brake fluid be getting past this piston and leaking out the front? I'm at a complete loss as to how exactly this component works. I'm not sure if I can add an o-ring to keep it from leaking or not. Any help would be greatly appreciated.

Thanks - Matt
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1972 Chevy Cheyenne SWB - Build: Porterbuilt State 1 Front & Rear, Bolt in Notch, McGaughys 2.5 Drop Spindles, Boyd Welding Fuel Tank

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Old 07-21-2015, 08:33 PM   #5
leftybass209
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Re: New Proportioning Valve Leaking

I just replaced my metering valve as well, problem solved. The hole that the pin protrudes through has nothing to do with why it's leaking there's nothing you can add or modify that will prevent it from leaking. The fluid leaks from deeper inside the unit. Glad to hear you fixed it.
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Old 10-26-2017, 07:31 AM   #6
vpapa57
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Re: New Proportioning Valve Leaking

Hi I am experiencing the same problem with my prop valve (purchased kit from Pirate Jacks) leaking out the front (now I have to refinish my inner fender well again) thought I had it fixed seemed to be fine for a couple of weeks and then started leaking again. What did you replace the metering valve with? Was it a different valve/size from the kit? Was the problem due to a faulty metering valve or was it a size issue? Do you have a part # etc? Sorry I don't know much about these devices, I had my brakes installed by a professional repair shop. I don't want to go back and forth with this issue and hope to resolve it with the replacement metering valve. Any help would be greatly appreciated. Thanks in advance, Vinny
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Old 10-26-2017, 10:02 AM   #7
B. W.
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Re: New Proportioning Valve Leaking

The issue is poorly made valves (dare I say chinese?) Does anyone offer made in USA valves?
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Old 10-26-2017, 10:57 AM   #8
Jcfcamaro
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Re: New Proportioning Valve Leaking

When I restored my 67 camaro I sent all my factory parts master cylinder, proportion valve, hold off valve, front discs to Lone star caliper in Texas. Not one problem at all. They specialize in corvette and camaro stuff. But when I called them for my 72 k10 they didn't want to work on these parts as they said they don't handle those types of brake parts. So I did some checking around and ended up going with Karps brake in Upland Ca. Had all my parts restored and powder coated. I have not installed them yet but they look great and they will stand behind there work.
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Old 10-26-2017, 11:25 AM   #9
MikeB
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Re: New Proportioning Valve Leaking

Wow, that's scary stuff. Definitely a good reason to rebuild like Jcfcamaro did. That's assuming you already have a factory valve.

Heck, when I converted a 69 C10 to power disc brakes around 1995, I got all the parts off a 71-72 junkyard truck. To this day, the prop valve still works fine. The booster diaphragm started leaking in the late 90s, so I had it rebuilt. I replaced the master cylinder sometime around 2012 for no reason other than the thing was very rusty. Found an NOS Raybestos-labeled M/C that was in a very nasty box that was nearly falling apart. Think I paid $17 for it at RockAuto! It's tough to beat those old USA made parts.

Hard to believe Pirate Jack doesn't immediately stop selling the prop valves and do a recall on them. I mean their liability would be HUGE if one of these things fails during a high speed stop.
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Old 10-26-2017, 11:44 AM   #10
Andy4639
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Thumbs up Re: New Proportioning Valve Leaking

Matt this was the problem with mine at the beach last year remember. I bought a proportioning valve with out the front rubber boot port. There is no need in it anyway. Buy one without it.

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Old 10-26-2017, 09:32 PM   #11
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Re: New Proportioning Valve Leaking

You could also do something like this Wilwood unit too, http://www.wilwood.com/MasterCylinde...emno=260-13190
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