Never had this much trouble with brakes

[bd]

Previously, you posted there was a lot of gunk in the combination valve when you took it apart.  What did you use to clean it?

[Breadfather]

Sprayed it out with brake parts cleaner and re lubed all o rings with brake fluid.

[Chuck Step-a-side]

Have you tried taking off the bleeder fitting from the rear cylinder and checking to see if it's clogged?  Then check to see if fluid will come out of the cylinder without the fitting. Replaced the bleeder fitting?

[roundhouse]

The master cylinder push rod could be adjusted improperly
Closing off the rear port inside the MC ?

At this point I'd just gut the distribution block and see if that works


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[Breadfather]

The wheel cylinders are new and thus so are the bleeders. The rear line is free from obstructions, I have tested. The master cylinder is now new and fluid is flowing from the rear section of the master like a champ.  Which brings me to the combo valve.

If I "gut" the valve in order to get fluid to the rear, and then re assemble it, do you think that will build up enough pressure in the rear section to prevent the valve from tripping again when I have to re bleed it?   I am assuming that will affect the proportioning part of the valve and I will then have too much pressure to the rear brakes?

[jetmech]

Did you replace the rear rubber hose? I quickly read the entire post but I could have missed it.

[BBM3]

Maybe I missed it but are you holding the metering valve open while bleeding?
Pages 5-7, 5-8, and 5-16 in the 1973 Light Truck Service Manual.
The same procedure should apply to your '77

http://www.73-87chevytrucks.com/techinfo/7387CKMans//Service/ST_330_73_1973_Chevrolet_Light_Truck_Service_Manual.pdf#page=273

[Breadfather]

Maybe I missed it but are you holding the metering valve open while bleeding?
Pages 5-7, 5-8, and 5-16 in the 1973 Light Truck Service Manual.
The same procedure should apply to your '77

http://www.73-87chevytrucks.com/techinfo/7387CKMans//Service/ST_330_73_1973_Chevrolet_Light_Truck_Service_Manual.pdf#page=273

Thank you for the link, it definitely helps me understand how the valve operates.  It is making me more and more convinced that there is something wrong with the valve.  The pin that is supposed to be sticking out of the front of the valve is and has never been sticking out of the valve since I've begun working on it.  Nothing I have done has caused any movement in that pin.  I think I am going to pull the whole valve again and soak it in denatured alcohol for a while to see if I can get it to free up, if not.  It is new valve time.

As far as the rear hose, I do not think that is the issue as I have been able to push air and fluid through the entire rear section once I disconnected it from the valve.

[BBM3]

You are welcome.
I am bleeding the brakes on my '75 tonight or tomorrow.
I just need to whip something up to hold the metering pin pressed in while I bleed the brakes.
The metering pin on mine is covered with a rubber cap. I can feel it press in when I push and return when I release it.
 

[Breadfather]

Okay, tonight I pulled the combo valve and disassembled it and soaked it in de natured alcohol for a while.  That didn't help, still no fluid through the rear section of the valve.  Convince that the valve is the issue, I cut the red plastic metering or proportioning stem out of the rear section of the valve.  The thought was I would be replacing the valve anyways I might as well see if I can get fluid to the rear while I wait for the new valve.  I was able to get fluid to the rear brakes finally.  After many headaches of getting all the air out of the lines, with the wife pumping and me bleeding I finally had a zero bubbles at the rear brakes. Everything else was bled as well.  I noticed when we were bleeding the rears that the flow was still not that strong but better than before. 

Once all the air was out, I started the truck up and put it in drive(on Jack stands with no rear wheels) and I still could not get the rear brakes to stop the axels.  I figured if anything, they would lock up easy with the combo valve gutted.  They did slow down more than before but would not stop, could this be the valve causing this because of my doctoring? Is it possible that the rear rubber hose could be causing this issue?  I blew air through the rear lines and verified there is no blockage, but could this be the swelling I've heard about?  I am 99% sure that the rear drums are adjusted properly as they are hard to spin and I can hear the shoes drag a bit on the drums as well. 

New master, new rear steel lines, new rear everything in the drums.

[Don5]

You have checked the hard brake line going from the prop valve back to the rear rubber line for leaks? I would replace the rubber brake lines on the front and the rear. They will swell on the inside and you can't see it until you take them loose and pump the brake. The fluid will either trickle out or not come out at all.

I just went through the same thing that you are doing with my truck. I replaced rear hard lines from the prop valve back, the rear flex brake line, the hard lines out to the wheel cylinders, new rear wheel cylinders, new rear brake shoes and all new hardware.

I replaced the front calipers, brake pads and front flex lines. I replaced all of the rubber lines with braided stainless lines.

[Breadfather]

Just installed new rubber rear hose and the flow is better but still can't get rear brakes to engage. I pulled one of the drums and had the wife push the pedal and I did not see the wheel cylinders do anything....could this still be a result of the prop valve since I gutted it?  It is hard to tell if there are any leaks on the main rear steel line as there is so much other gunk and fluid on most of it or its behind heat shields, frame pieces, etc.....I'm about ready to start driving it around with no rear brakes.

New master, new rear hose, new rear axel lines, new drums, new everything in drums, still no rear brakes.  They are adjusted properly.

[jaredts]

I would just go ahead and get a new valve.  You likely want a pv2.  I got mine from cpp and was very happy with their service.

[VileZambonie]

Make sure the rear brakes are assembled correctly and properly adjusted. Replace the combination valve.

If you bleed it at the master you get good pressure?

[Breadfather]

Make sure the rear brakes are assembled correctly and properly adjusted. Replace the combination valve.

If you bleed it at the master you get good pressure?

Yep good pressure at the master great pressure up front.  I thought gutting the valve would at least get me to be able to stop the rear wheels or lock them up...but not so.  I put the wheels back on and drove it around today and the pedal is good, very solid.  It stops better than it did before but I think that is because the new master...I'll update after I get new valve installed in a few weeks.