'69 brake distribution valve function

[Verne_Frantz]

I asked this question on the Chevelle site but no answers yet. My ELC has drum-drum brakes and I can't seem to get the rears bled properly. There is almost no flow of fluid. The system is all stock with a rebuilt master and new wheel cylinders. My question is: does that valve partially close off the front or rear if there is a leak or an open line? I've looked at the pin inside that is under the switch and all I see is a straight smooth pin. I don't see anything that would cause it to activate the switch. I want to know if that valve could be my problem or if I should look elsewhere.

thanks
Verne

[jl8z28]

Take the master cylinder cover off and open the bleeders on the back just let it sit I usally leave it over night unless the fluid starts to come out sooner then if still dosent work get one of the brake bleeders that draws the fluid from the bleeder screws

[ssl78]

Did you check the rubber brake line at the rear that goes into the junction block. That line gets plugged and will not let fluid go thru

[Verne_Frantz]

I plan on checking that too, but I NEED to know if that distribution valve can close off flow.

I have no bleeder screws on the master.

Verne
http://www.yenko.net/ubbthreads/pics/usergals/2016/10/full-1145-50585-img_5495.jpg

[jl8z28]

That doesn't matter you can draw the fluid from the bleeder on the rear cylinder

[Verne_Frantz]

Now I understand what you're saying. You're talking about gravity bleeding.

Before I check anything else, I'd like to know if that valve could be preventing the fluid flow to the rear. IF it is, no kind of bleeding will work. THAT is the question I'm looking for an answer to.

Verne

[m22mike]

Verne
Here is a 70 differential pressure valve. I think 67 through 70 are the same inside, it is just a simple spool valve. You can see the internals here. It can restrict fluid if the spool is shifted from differential pressure, and they can stick. They are not hard to take apart and clean.

Distribution / press diff block (https://www.musclecarresearch.com/gm-pd-valve-rebuild)

[Verne_Frantz]

Thanks Mike. Those components are very similar to mine but a little different. On the plus side, I can see the smooth brass rod directly under the safety switch, so it appears that it is not diverted to one end or the other (blocking of any flow). IF that is the case, I'll assume the valve is not my problem. I'll look for kinks in the line to the rear first, then replace the rear hose and see where I am after that.

Verne

[jl8z28]

I had the same problem with my camaro and before you change something try what I said

[ssl78]

Try breaking the steel brake line loose where it goes into the rear rubber line see if you get a good flow of fluid there.

[Verne_Frantz]

I did the gravity thing and both rear sides dripped out continuously, so I closed them off and then pedal bled it. Not as much flow as I thought it should have but it did bleed. I'll wait for the road test and see what happens. The valve piston stayed centered through all of it. If the damn thing is stuck in the center that would be FINE with me.

Verne