do proportion valves go bad?

[v-man]

I tried to bleed my brakes and could only get one corner to take. Do these prop valves go bad?

[75Dart440]

I have never heard of one failing.....but it could blocked internally or corroded.

If it is a rear corner that isn't bleeding, that would rule out the prop valve as a single line from the valve feeds the rear brakes unless someone has modified the brakes from factory configuration.   Look for a pinched line from the divider block on the rear axle assembly out to the wheel that will not bleed.

If it is a front corner that will not bleed, then check for a pinched metal line, blocked bleeder screw or bad caliper. 

If the bleeders haven't been opened for many years, you may need to stick a small rod into the  bleeder  or remove the bleeder and clean it real good.  I have had them fill up with road grime and rust and not want to bleed.

[v-man]

i put new bleeders in, so that can't be the problem.
The rears are dry and one of the fronts is dry. I put new lines in. Something is just wrong

[75Dart440]

i put new bleeders in, so that can't be the problem.
The rears are dry and one of the fronts is dry. I put new lines in. Something is just wrong

Sounds like the prop valve has a blockage inside.  Was the brake fluid allowed to become contaminated with water and left to sit for a long time?

I have had cases where I removed the bleeders and still couldn't get fluid out of the caliper or wheel cylinder.....removed the bleeder, and poked around inside the hole with a peice of wire and got a nice rusty mass out of it.

[PureGTS]

  If the system was left open for a while, exposed to the elements, it could corrode (brass) internally or get some debris in it and cause the shuttle valve to stick towards one side or the other. Another misnomer is the thing everyone calls a "Proportioning valve" (it has a single wire going to it from the brake warning lamp in the dash) is really not a proportioning valve. It is a brass housing that is basically a brass "T". Only it really is  a five way "T". (One line in for the rear brakes, one line out for the rear brakes. One line in for the front brakes, two lines out: one for each of the front brakes.) It holds a shuttle in it that is supposed to move in the direction of least resistance (pressure) and ground out a probe sticking into the bore that would touch the shuttle if the pressure differentiated from one end or the other, if, say, there was a leak. Thereby turning on the light in the dash. Take one apart some time and measure the bore and guts and line holes. You'll find no differences to meter anything.

[v-man]

it sounds like i may have a clogged bleeder valve. I used all new lines and new fluids. The only thing that I re-used was the prop valve. are there any adjustments?

[75Dart440]

There are no adjustments to the "Proportioning" valve.......(Pure GTS is correct in that it is merely a distribution block).  I would either try replacing the distribution block or if you cannot find one, just plumb the rear line direct from the master cylinder (put a Wilwood or Mopar Perf adjustable prop valve in line to the rear) and put a brass T fitting on the front lines.

I re-used my old drum brake distribution valve merely cause it was still there and was working.  But I have an adjustable unit in the rear line to control rear brake lockup.  If the distro block ever gives me fits, it is outta there and a T block going back in it's place.