brake distribution block leak

renchjeep

New Member
Dec 21, 2020
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aguanga, CA
Hey, guys and gals. Working on my 72 Mustang Grande 351 2v front disc/rear drum power brakes. Brake master cylinder was nasty with gunk inside, and had rusted on the lid sealing surface, so replaced it with a new unit. That took a few tries, with getting the wrong ones sent to me twice, and one that I though failed right out of the box. Well, turns out that "failed" one was fine (apparently), as I discovered brake fluid leaking from the pressure switch on my original distribution block. I know that no fluid should get to that switch. even if the shuttle valve inside reacts to low pressure on one side by moving and activating the switch, turning the brake warning light on. So, here we go.....buy a new (cheap, like 50 bucks) distribution block, swap it out, same problem, leaking from switch. That supplier sent me a replacement for 10 bucks to cover shipping, tells me to just keep the defective one. LOL. The replacement does the same thing. Buy more expensive distribution block (around 75 bucks), same problem. Buy a rebuild kit for my original, and some of the o-rings don't look exactly right...I may have ordered wrong on that one. I have now ordered a rebuild kit for the entire valve from Muscle Car Research, distribution side and control valve side. I figure I will try once again to rebuild my factory unit, both sides, this time with hopefully the correct parts. The bores look good, cleaned up nicely. I suppose my question at this point is have any of you had issues like this, over and over, or am I just special? If anyone else has played this game, what was the final solution? Thanks in advance.
 
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Rebuild it ,but make sure you have brake fluid resistant seals . I would find a race shop that knows what is needed ...not Autozone haha
 
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65-Fstbk

Active Member
May 20, 2007
311
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39
Vancouver, B.C. Canada
Hey, guys and gals. Working on my 72 Mustang Grande 351 2v front disc/rear drum power brakes. Brake master cylinder was nasty with gunk inside, and had rusted on the lid sealing surface, so replaced it with a new unit. That took a few tries, with getting the wrong ones sent to me twice, and one that I though failed right out of the box. Well, turns out that "failed" one was fine (apparently), as I discovered brake fluid leaking from the pressure switch on my original distribution block. I know that no fluid should get to that switch. even if the shuttle valve inside reacts to low pressure on one side by moving and activating the switch, turning the brake warning light on. So, here we go.....buy a new (cheap, like 50 bucks) distribution block, swap it out, same problem, leaking from switch. That supplier sent me a replacement for 10 bucks to cover shipping, tells me to just keep the defective one. LOL. The replacement does the same thing. Buy more expensive distribution block (around 75 bucks), same problem. Buy a rebuild kit for my original, and some of the o-rings don't look exactly right...I may have ordered wrong on that one. I have now ordered a rebuild kit for the entire valve from Muscle Car Research, distribution side and control valve side. I figure I will try once again to rebuild my factory unit, both sides, this time with hopefully the correct parts. The bores look good, cleaned up nicely. I suppose my question at this point is have any of you had issues like this, over and over, or am I just special? If anyone else has played this game, what was the final solution? Thanks in advance.
Did you ever get this solved? I am having the same problem and am about to lose my mind. I started with an original equipment block Circa 1970 and it leaked at the switch. Ordered a rebuild kit and rebuilt it, nope still leaked. Took it apart and cecked everything 3x and 3x still leaked. So I ordered a new one on-line and used a stopper in where the switch goes to prevent the piston from fully moving to one side. Leaked. So kjust like you the guy sent me a new one, leaks.

I'm at my wits end. Hopefully you solved it.
 

renchjeep

New Member
Dec 21, 2020
3
0
1
52
aguanga, CA
Did you ever get this solved? I am having the same problem and am about to lose my mind. I started with an original equipment block Circa 1970 and it leaked at the switch. Ordered a rebuild kit and rebuilt it, nope still leaked. Took it apart and cecked everything 3x and 3x still leaked. So I ordered a new one on-line and used a stopper in where the switch goes to prevent the piston from fully moving to one side. Leaked. So kjust like you the guy sent me a new one, leaks.

I'm at my wits end. Hopefully you solved it.
Nope, never resolved it. Well, I did resolve it....kinda. I BAILED on the job after I had two "new" units leak from the switch, then rebuilt the original with a kit from Muscle Car Research, used the thread-in bolt with the end to hold the shuttle valve while I bled the brakes, and it still leaked! I didn't even bother to put the switch back in, as the fluid was coming out of the "holding bolt". Yes, the shuttle valve was centered, and held firmly in place by that bolt. The owner of the 72 Mustang (who is actually not me, but my neighbor) said she has another mechanic who specializes in "older cars". I wished her luck, and asked her to let me know when and if he manages to fix it successfully, and HOW. If and when I hear back, I will post here for sure. Anyone else with a success story, PLEASE post it here! Drove me nuts, and honestly still is. For such a seemingly simple thing to beat me.....well, it just SUCKS!
 

65-Fstbk

Active Member
May 20, 2007
311
23
39
Vancouver, B.C. Canada
Nope, never resolved it. Well, I did resolve it....kinda. I BAILED on the job after I had two "new" units leak from the switch, then rebuilt the original with a kit from Muscle Car Research, used the thread-in bolt with the end to hold the shuttle valve while I bled the brakes, and it still leaked! I didn't even bother to put the switch back in, as the fluid was coming out of the "holding bolt". Yes, the shuttle valve was centered, and held firmly in place by that bolt. The owner of the 72 Mustang (who is actually not me, but my neighbor) said she has another mechanic who specializes in "older cars". I wished her luck, and asked her to let me know when and if he manages to fix it successfully, and HOW. If and when I hear back, I will post here for sure. Anyone else with a success story, PLEASE post it here! Drove me nuts, and honestly still is. For such a seemingly simple thing to beat me.....well, it just SUCKS!
Thanks for the update. It's somehow nice to know I'm not alone. I'm thinking of switching to an adjustable proportioning valve. There's some out there that take both lines from the Master Cyl and then after you bleed it the dial is used to dial down the pressure to the rear drums. It still has a switch port but looks like that is sealed. I agree, for such a simple thing this is sooo frustrating. I will post here to when I resolve.
 

renchjeep

New Member
Dec 21, 2020
3
0
1
52
aguanga, CA
Thanks for the update. It's somehow nice to know I'm not alone. I'm thinking of switching to an adjustable proportioning valve. There's some out there that take both lines from the Master Cyl and then after you bleed it the dial is used to dial down the pressure to the rear drums. It still has a switch port but looks like that is sealed. I agree, for such a simple thing this is sooo frustrating. I will post here to when I resolve.
Yes, nice to not be alone. I was thinking of an aftermarket adjustable valve. If her other mechanic cannot fix it, that's exactly what I will do. Looking forward to hearing and maybe seeing your solution.
 

manicmechanic007

Active Member
Sep 26, 2017
294
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61
You are overthinking this. Although Ford made thousands of proportioning valves, all different. About a hundred should work for your 72. Advise go to the junkyard find a truck valve (68-86 or so) and slap it on. Several will work even the ones without disc brakes will be better than your stuck or leaking valve. I have a 56 Ford Mainline that has 03 E350 brake parts.