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Discussion Starter #1
Greetings,
I am posting here for the infinite wisdom of the Impala community. I have a 2003 GMC Sonoma truck and the brake proportioning valve is leaking. Seems as if finding a new or rebuild unit is not going to happen.

So I may attempt to rebuild the unit and hopefully it is just a leaking o'ring. With that being said, what types of o'rings are compatible with brake fluid?
Viton, Nitrile, Neoprene, Ethylene Propylene Rubber(EPR), PTFE etc?

Thanks,
Michael
 

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Greetings,
I am posting here for the infinite wisdom of the Impala community. I have a 2003 GMC Sonoma truck and the brake proportioning valve is leaking. Seems as if finding a new or rebuild unit is not going to happen.

So I may attempt to rebuild the unit and hopefully it is just a leaking o'ring. With that being said, what types of o'rings are compatible with brake fluid?
Viton, Nitrile, Neoprene, Ethylene Propylene Rubber(EPR), PTFE etc?

Thanks,
Michael

EPDM (Ethylene-Propylene Diene Monomer) rubber is what you want. You're generally not going to find seals made from this material at your local auto parts store. I make rebuild kits for a number of applications (not yours, though) and have a pretty good collection of many sizes. If you can figure out what you need I may be able to help.
 

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Bob, It's noted 0 stock.

Mark: Snowman-33

Lol - there's a lot of that going around. And thanks. What struck me search-worthy is checking (and you confirmed) that you can't get parts for even a 15-year old Chevy? The dealer can likely get one though. For say, $400?


For the OP, it may be out there, but just a thought to leave the valve intact while confirming the lines/fittings are not simply corroded or loose. Latter seems way more probable than the valve letting go.
 

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Lol - there's a lot of that going around. And thanks. What struck me search-worthy is checking (and you confirmed) that you can't get parts for even a 15-year old Chevy? The dealer can likely get one though. For say, $400?

I found that strange too. Says alot about the future.


For the OP, it may be out there, but just a thought to leave the valve intact while confirming the lines/fittings are not simply corroded or loose. Latter seems way more probable than the valve letting go.
I recently had a situation that backs this up. Check the simple things first. I told my wife several days ago that my truck was like her. Old, creaks & growns and drips a little. but it's faithful. I went out to start it and WTH? it cranked and stopped. No lights except the dash. I thought I heard a snap when it happened. Started checking fuses & relays. Turned out it was loose cable to the battery.

Mark: Snowman-33
 

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A little off the subject,but when I deleted the ABS off my C/K pickup. Added an aftermarket adjustable proportion valve on rear brake circuit. If/when rear brakes start to lock-up,then take a little percentage of brake force off. Continue until periodic adjustments like this until satisfied.
 

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Discussion Starter #9
Thanks guys you are helpful as usual. I will probably go to a yard and grab one then call on SAH62 to see if he has the proper o'rings.

FYI, the valve is leaking from the rearmost cap. When I press the brake, I see a pin protrude out the end and then I see a few drops of fluid. I do have a bad feeling that this may be a symptom of another problem.

I will get under the truck tonight and see if I have another leak. I have read that the pin should not show out of the valve unless there is a pressure loss somewhere else in the system.

Thanks again,
Michael
 

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Is there a an oncar diagnostic and instruction such as old prop valves had for "recenterng" subsequent to getting thrown over after pressure loss to one end?
 

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Discussion Starter #11
I finally found a bone yard in Texas that had a combination proportioning valve from a 2003 S-10 with relative low mileage(117k). I replaced the Master Cylinder and the proportioning valve. I am back to normal. I believe that the master cylinder was leaking internally and the proportioning valve was leaking out of the rear port.

I took apart the proportioning valve and only a single o-ring. The other portions are rubber discs. I need to see if anyone has the replacement discs to rebuild the valve and just put on the shelf for later.

Thanks for the insight.

Michael
 
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