leaking proportioning valve
Thread Starter
Racer
Joined: May 2007
Posts: 296
Likes: 4
From: London Ontario
leaking proportioning valve
I put all new brake lines on my 75, I went to bleed them and the proportioning valve was leaking. I tightened all the lines up and tried again, still leaking. found that the leak was coming from the actual valve. I took a picture of the part that was leaking and found a little hole in the side of it. I'm not sure why its there or what it does but I think its leaking from there. Can anyone help. thanks
This is the outlet for the rear brakes
This is the outlet for the rear brakes
Last edited by curtis75; Apr 11, 2010 at 06:04 PM.
Le Mans Master
Joined: Mar 2001
Posts: 6,640
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From: Ann Arbor Michigan
That's a vent for the atmospheric cavity inside the hex plug. There is a spool with 2 o'rings on it, one or both are leaking. The assembly is pressed together and can not be taken apart.
Gary
Gary
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Le Mans Master
Joined: Mar 2001
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From: Ann Arbor Michigan
Perhaps poster fogaley was referring to the 2 o'rings on the diff piston and the one on the end plug as shown in this photo, they are easy to change. I hope he reports back so we all know.
Gary
Gary
Le Mans Master
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From: Ann Arbor Michigan
DON"T buy hardware store o'rings. Many towns have commercial parts supplers (Rodger Zatkoff is ours in Detroit) that sell o'rings of the correct compound and hardness. You can Google 'O'rings and the city you live in to find them. You might have to buy 25 bucks worth (which would be enough to rebuild a 100 valves). Gary
Le Mans Master
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From: Ann Arbor Michigan
Thanks to a fellow Forum member who donated his used valve to the cause, I was able to get it apart with no problem. Use a 1/8" diameter dowel pin (about 2" long) and insert it in the outlet port (see photo below) and press the retainer out by supporting the end plug with a 3/4" socket. I used a press, but a vise will do as it didn't take much force to push it apart. The last photo shows what the parts inside look like. I could probably do some type of WORD document showing how the whole thing comes apart and what's needed to rebuild it if anyone would be interested.
Gary
Gary
Last edited by Duke94; Jul 10, 2010 at 08:10 PM.
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Sometimes you gotta bite the bullet and buy a new one, that's what I did and should last another 30-100 years who knows I'll be long gone. I f'upped the threads installing new brake lines otherwise the original block would still be in there 
Last edited by MotorHead; Jul 10, 2010 at 09:07 PM.
Le Mans Master
Joined: Mar 2001
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From: Ann Arbor Michigan
[QUOTE=...Roger...;1574656182]Duke are you sure the internal o rings are what is causing the external vent to leak ?
QUOTE]
Yes, the spool inside the end plug has an o'ring at each end with the spring in an atmospheric chamber in between. The spool moves with each brake apply (above the knee point of the valve when it starts to proportion) so if either one of the o'rings wears out, brake fluid leaks into the this cavity which eventually blows out the dirt seal on the side of the hex plug and fluid leaks on the ground.
Gary
QUOTE]
Yes, the spool inside the end plug has an o'ring at each end with the spring in an atmospheric chamber in between. The spool moves with each brake apply (above the knee point of the valve when it starts to proportion) so if either one of the o'rings wears out, brake fluid leaks into the this cavity which eventually blows out the dirt seal on the side of the hex plug and fluid leaks on the ground.
Gary
Last edited by Duke94; Jul 11, 2010 at 09:13 AM.
Pro
Joined: Jan 2010
Posts: 518
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From: Panhandle
Gary,
I'm game. I have two of these in my garage which the "inside" o-rings have disintegrated. Needed the O-ring tip! Thanks. I have two sets of O-rings. See photos -- would any of these work? The green ones are for AC units and the label on the black ones says for hydraulics?
Would love to see a word document so I can replace mine and finally get that light out.
Pauldana: Couldn't get your link to work -- what item is $60.?
Motorhead: I agree sometimes you have to bite the bullet. However, love fix'in things TOO as long as we mitigate the risk of a catastrophic failure. Does anyone see the potential for "a brake fluid blow -out?"
TI
I'm game. I have two of these in my garage which the "inside" o-rings have disintegrated. Needed the O-ring tip! Thanks. I have two sets of O-rings. See photos -- would any of these work? The green ones are for AC units and the label on the black ones says for hydraulics?
Would love to see a word document so I can replace mine and finally get that light out.
Pauldana: Couldn't get your link to work -- what item is $60.?
Motorhead: I agree sometimes you have to bite the bullet. However, love fix'in things TOO as long as we mitigate the risk of a catastrophic failure. Does anyone see the potential for "a brake fluid blow -out?"
TI
Le Mans Master
Joined: Mar 2001
Posts: 6,640
Likes: 287
From: Ann Arbor Michigan
Gary,
I'm game. I have two of these in my garage which the "inside" o-rings have disintegrated. Needed the O-ring tip! Thanks. I have two sets of O-rings. See photos -- would any of these work? The green ones are for AC units and the label on the black ones says for hydraulics?
TI
I'm game. I have two of these in my garage which the "inside" o-rings have disintegrated. Needed the O-ring tip! Thanks. I have two sets of O-rings. See photos -- would any of these work? The green ones are for AC units and the label on the black ones says for hydraulics?
TI
Gary
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From: Dayton, Ohio
[QUOTE=Duke94;1574659546]
Thanks , thats nice to know.
Duke are you sure the internal o rings are what is causing the external vent to leak ?
QUOTE]
Yes, the spool inside the end plug has an o'ring at each end with the spring in an atmospheric chamber in between. The spool moves with each brake apply (above the knee point of the valve when it starts to proportion) so if either one of the o'rings wears out, brake fluid leaks into the this cavity which eventually blows out the dirt seal on the side of the hex plug and fluid leaks on the ground.
Gary
QUOTE]
Yes, the spool inside the end plug has an o'ring at each end with the spring in an atmospheric chamber in between. The spool moves with each brake apply (above the knee point of the valve when it starts to proportion) so if either one of the o'rings wears out, brake fluid leaks into the this cavity which eventually blows out the dirt seal on the side of the hex plug and fluid leaks on the ground.
Gary