Resetting a 67 distribution block ?

[Daddy Brim]

I have 67 C-20 a while ago I had front brake failure, broke rubber line. since then I have replaced all rubber lines, calipers, shoes, and springs. I'm trying to bleed the system and it appears that I have all of the air out, not seeing any air bubbles when I open the bleeder. It appears the amount of fluid coming out the back is more than the front. There is no brake peddle, and I wound doubt it is the master cylinder as everything was fine before brake line broke. I have tried to do some research some say the distribution block needs to be reset others there is nothing to reset. What do I need to do to fix these brakes? I'm at my wits end. This is the distribution block that is in my truck.

[Daddy Brim]

Maybe the title should say, No peddle need help with brakes

[JimKshortstep4x4]

The distribution block should allow some pedal regardless of whether it is centered or not.

I suspect that you still have air in the lines and would suggest rebleeding starting with the master cylinder.

Jim

[Daddy Brim]

The master cylinder never went empty. Do you think it is possible for air to get all the way to the master cylinder from the broken line? The brakes were pumped a lot to get the truck stopped and to get it home.

[67Slider]

IIRC that distribution block doesn't have the ability to center. It either works or doesn't. The disc brake valve has the ability to re-center.

[Daddy Brim]

Originally Posted by 67Slider

IIRC that distribution block doesn't have the ability to center. It either works or doesn't. The disc brake valve has the ability to re-center.

This is what I thought. So I'm guessing there is a lot of air still in the system.

[ceenerman]

i'd start with the MC. than hook the block and bleed.than the lines.

[jocko]

also, if I'm not mistaken, that block was not a distribution block in 67 - it's just a brake pressure transducer, will send a signal to the light if there's a total pressure loss on either circuit to let you know you're running on a single circuit (front or rear). 67 was the first year for dual res master cyls - and the setup was still drum/drum, std until 72 when disk/drum became std (option in 71). Anyhoo - my point being, there is no adjustability in this setup - and since it is a drum/drum setup, the "proportioning" is done by the master cylinder itself - taken care of by the way in which the piston uncovers the front/rear ports when you depress the brake pedal.

However, here is one thing ot make sure of - and it probably has no real relation to your specific problem - make sure the front brakes are hooked up to the rear port and the rear brakes are hooked up to the forward port (of the mc) - this is what ensures proper proportioning, reversing it is akin to setting a prop valve too much biased to the rear, and you won't want that.

As for having NO pedal at all, I would ask how much bleeding have you actually done yet? When I replaced an entire system, I was amazed at how long it took to get the air out completely - the rears came back first, as you'd expect since that is the bleeding order. If there's any question in your mind about whether or not you've bled enough, then I'd go do it some more - but I'm assuming you have probably bled it to death, and so that's probably not the issue. It is possible that in the process of doing all you've done that the piston of the mc was pushed in and, if it's old, hung up on a groove in the bore. Is your pedal just dropping to the floor (or at least to an intermediate position) with zero resistance? Does it pick up any resistance before it hits the floor? This could be a hung mc, which should be replaced (or honed if $ tight). Not sure I've helped, but there you go. Good luck. Brakes can be nerve-racking!!

[Daddy Brim]

I'm going to bleed entire system starting with master cylinder. Have not tried that yet. I think there is still air in there.

[Daddy Brim]

It is fixed, it turned out to be air in the master cylinder. The line failure was the rubber line on the left front, I did not think air could make it all the way to the master cylinder. So I learned something today.

[425HP409]

The valve in question for a drum/drum brake system is a pressure differential valve. It has a valve in it that will stay centered with equal pressure front and rear. It will move to one way or the other if one end of the brake system has a pressure drop, this will provide a ground circuit to the brake warning lamp and it will light up notifying the driver that there has been a brake pressure loss. When the loss of pressure is repaired the valve can be recentered by firmly depressing the brake pedal a couple of times.

[jocko]

Originally Posted by 425HP409

the valve can be recentered by firmly depressing the brake pedal a couple of times.

Now THAT I did not know, thanks for posting that!

[CKfan]

Old thread but very helpful to those of us with a manual drum/drum brake system and the old "distribution block" (not a proportioning valve).

Was confused at first but read to the end for clarification.

Solid information.

[custom10nut]

Here’s a question about distribution blocks.
On a Drum/Drum System, is there a difference in the DB between Manual and Power brakes?

I know that Disc/Drum brakes require a Proportioning Block, which is different than a Drum/Drum setup

[68 P.O.S.]

Originally Posted by custom10nut

Here’s a question about distribution blocks.
On a Drum/Drum System, is there a difference in the DB between Manual and Power brakes?

I know that Disc/Drum brakes require a Proportioning Block, which is different than a Drum/Drum setup

As far as I know, there's no difference bewteen power and manual. It only distributes the fluid in the system, doesn't affect pedal effort.

Disc/drum brakes require a combination valve. It's a 3 in 1 valve that has a distribution block at the front, a brake waring switch in the middle, and a proportioning valve in the rear.