brake proportioning valve leaking

[FORDification]

First I need to clarify my terminology. The second pic I posted above isn't actually a proportioning valve, it's simply a metering valve. Ford didn't use an actual proportioning valve until '73. And the dentside-era piece is actually a combination valve, which includes the metering valve and proportioning valve. Thought I'd better get the terms right to avoid confusion.

In all the trucks I've parted out, I haven't had an F250 with factory discs and metering valve, so I'm not entirely certain on how those front lines are routed. However, now that I think about it, it does make sense that there would only be one line coming from the distribution block out to the metering valve for the front brakes, and then tee off that to go to the individual front calipers. The question is...how did the factory cap off #3? I'd have to guess they used a plug and not a bolt. I'll have to see what I can find out about that.

[1971ford]

Thanks Keith. It looks all original to me but what do i know...
Being that i can crank the bolt down on a crush washer and barely apply the brakes and brake fluid shoots out between the bolt/block, i would think a simple plug would shoot out with the weight of the brake pedal itself though
Do you think something is wrong with my brake setup causing ridiculous pressure to that bolt/plug?
ok ok i'll give you some time to research

[fordman]

i do think his may be hooked up right. as both his front brakes for disc would run to his metering block on the front crossmember he wouldnt have need for the extra #3 fitting. to go to the other front brake. i think #3 is only used on drum brakes. that doesnt look like a bolt. #3 is a flared fitting just like the others. it would require a flare fitting plug. the flare fittign plug would do all of the sealign. a regular plug or bolt would not seat enough to keep it sealed. maybe the brake lines are clogged or the valve has stuck and is pushing pressure out #3. or the flare is damaged either on the plug or in the block.

[1971ford]

Fordman what you are saying makes sense, just one question for now.
I have the block out of my '69 f100 sitting on my work bench to compare (it has the #3 brake line), and the only difference is that instead of the bolt my '71 has it has a bolt with a line threading in it. The actual bolt seating to the block is the same on both.... so i don't see how a brake line fitting in the top of the bolt would help the bolt seating.

[fordman]

the brake lines are a flare fitting. they are special . flare fittings can only be capped or plugged with a special flare fitting plug or cap. but since yours was good it is probably not the "bolt" that is in it that is the problem. or maybe it is the probelm and it is finally leaking because soemone put the wrogn type of bolt in it. if i had a flare plug i could take a picture and show what it is suppose to look like. if you take yours out again take a picture of it. maybe i am wrong.

[FORDification]

Agreed...it's a special plug that you need, called an inverted flare plug. It looks like this:


http://www.fastenal.com/web/products/de ... 280&ucst=t

[1971ford]

You guys think that would fix the problem?

Honestly I don't think it would fix it and here's why i think that....
Simply because the bolt that is in it is definately the right thread and size and with the crush washer all torqued down intensely... yet brake fluid still spews out... so i don't see how the plug pictured would fix the problem? Looks to me like the exact bolt i have but hollow. hmm


Like Fordman said as well, the bolt has worked for years so i would think it's not the problem but again, like he said, maybe it just gave up. I'll try the plug since it's not a hard thing to do.

These pictures include the bolt out of the '71's block, but the block is out of my '69. The '71's block is still in the '71 and probably will be forever because it sure as hell doesn't want to come out without a MAJOR fight.
I guess they don't really show you guys anything now that we know what is being discussed but i'll post anyways




And one other thing. The bolt in my '71's block, if i remember correctly (i'll double check), the bottom of it is beveled in slightly so it's not like a normal bolt. the head of it is also taller than a typical bolt. and it's got some weird marking.

[fordman]

i wonder if the copper crush washer you used is too thick. so the flare plure isnt seating into the hole all the way.

[FORDification]

I'd sure like to see that bolt removed, to get an idea of what you've got, but here's what I'm thinking.

I don't think the plug I posted above screws directly into the block itself (and I suspect the bolt you have isn't supposed to either), but into the brass flare fitting that's supposed to be there to accept the brake line. The only difference is that instead of screwing the brake line into it, you're using the plug, which will mate perfectly with the flare on the inside of the fitting to seal it off.

Think of it this way....if you were to remove the distribution block from a drum-brake truck, that #3 port is going to have a brass fitting there for the brake line. Don't remove the brass fitting, just screw the plug into it.

[1971ford]

Okay I understand... my '69's block had that fitting in it.





The bolt plug is still in the truck's block so i don't have pics of that.
But still, that wouldn't stop it from leaking between the bolt or fitting and the block. That would just cap off the fitting just like how the bolt is capped off by a solid bolt head...
Any ideas on what i can try to do that might be making excessive pressure at that area of the block?
I think fordman suggested a stuck piston on the first page? I remember a long time ago a piston got stuck in one of these brake parts and my dad and I had to pull it off and blow the piston with compressed air to unfreeze it... if that happened again could it be the problem?

[70_F100]

If everything is seating together properly, it's possible that either the bolt/fitting you're using or the block itself may have a small crack.

I would think that's the best possibility, given that it just started leaking all of a sudden after all these years.

[1971ford]

It's a possibility, but i doubt it. Unless the crank is super close to the bolt head...
Only problem is I can't look at it that closely without pulling it and it's going to take a while to pull it. I might have to cut the brake lines and re-do them. such a PITA. I'm going to deal with it this weekend.

[fireguywtc]

Ya, this is all making more sense and is very intersting to follow.

Unless I am missing something, the pics you show of the top of the bolt shows threads and then a hole. That is actually the brass flare fitting the Kieth was taking about for the threaded flare fitting to screw into with the brake line. It looks like you are missing the plug that went inside of that adaptor. If you can find a true bolt to fill that hole or a bolt/pulg to go into that adaptor, you will be good to go.

[FORDification]

The pressure you keep referring to as excessive is normal...the brake shoes/pads HAVE to have a lot of pressure pushing on them to stop a 2-ton truck. Typical brake line pressures during a stop range from less than 800psi under "normal" conditions, to as much as 2000psi in a maximum effort. That's more than enough to squeeze past the threads of a bolt that might be compromised or worn. That's why brake fittings have the inverted flare...it allows a might higher seal rate than just a bolt (or plug by themselves) would.

And that's why at this point I'd suggest replacing the distribution block (since it's either cracked or has compromised threads) AND make sure that the replacement distribution block has the proper inverted flare nut and matching inverted flare plug. Do not just try screwing another bolt in there...or you'll probably be having this same problem again in the future.

[1971ford]

Okay...
I'll put the '69's flare nut deal on the '71's block then pick up a plug and install it and see if that works. If not (threads in block warn, block cracked, whatever) then I'll pull the block out. That's going to be a bad time