Brake light won't go out. Brake proportioning valve?

[Old Man Powell]

I'm back... and with more problems. So Brought Rooster home and the brake light was on. I can stop but no matter how hard I push on the brake pedal it will go half way and Rooster slowly comes to a stop. Now, regardless of that I finally rebuilt the rear brakes. When I pulled the rubber boots off of the wheel cylinders nasty old fluid came out. Looked like rusty, muddy water. Anywho, completely rebuilt wheel cylinders... new hardware... new brake shoes. Bled the system... everything looks great.

Back to the brake light. If you slam on the brakes the light goes out and you will come to an abrupt stop. However, the light comes back on. We started looking at the proportioning valve. From the diagram here on the forum it looks like it is stuck. The small rod with the ball at the end that comes out of the front of the "block" is not flush... the rod is all the way out. Thus I'm guessing it is stuck and directing all pressure to the front brakes. We opened up both front bleeders, slammed on the brakes and then closed the bleeders again. That did not get the rod to move. Next we did the same thing but with all the bleeders open. Still no luck. So, I'm guessing I need to take it off and take apart? Are replacements or parts available?

We checked the vacuum to both boosters and everything seems fine there.

So, again... thoughts/suggestions? All the brakes lines going to the booster are soaking in PB Blaster.

[Old Man Powell]

I read via Dave's webpage that i should not take this apart. Is there any way to clean and "bench reset?"

[Rickf1985]

The way to reset a prop valve is to figure out which is the offending side and then open a bleeder on the good side and slowly push the brake until the light goes out and close the bleeder. At that point the prop valve is centered and should stay that way as long as the brakes are all working and set correctly. And no leaks.

[Old Man Powell]

Still not 100% sure this is the source of my problem. Should the rod be sticking out? Mine is a good 1/4" out. Or should the ball on the end be up against the body of the unit (no rod protruding out)? We bled the entire system (more than once) and the light never came off and the problem still exist. Again, I've seen pics of similar combination valves and some have the rod sticking out and others do not. I got good fluid flow at each bleeder when bleeding the system. The fluid coming out of the rear (or front) brakes did not seem to be "restrained."

[DaveVA78Chieftain]

light is normally due to air in the lines.
Some ref info: http://dave78chieftain.com/ControlValves.html

[DRMousseau]

mmmmm,....  We often blame the components 'cause they're old, a bit rusty, or we don't fully understand how the systems are designed to work.

I too have a "brake warning light" that stays on all the time. It took a bit to track down, but it's because of a leaky faulty brake cylinder on the rear passenger side. Ya,.. I got no rear brakes at this moment. It's my next major repair. BUT, I have verified the function and operation of the distribution block and switch assembly along with the circuitry necessary.

Power is present at the distribution block switch when the Ignition key in turned on. If the switch is "centered", it is in the "normally open" position. While power IS present at the wire connection, the circuit to ground is incomplete, and the warning light remains out. If the switch is "triggered" in either direction, the circuit is closed and completed to ground.

IF the light is on as a result of the switch being triggered closed, you should be able to pull the wire connection from the distribution block and make the light go out due to open circuit. Battery voltage is present with the ign key on, and can be measured on this wire.

IF the light REMAINS ON when you pull this connector from the distribution block,.... then you have a short to ground somewhere in this circuit between the dash light and the distribution block. With the wire disconnected from distribution block, you can check for "continuity" of the switch, between the terminal post of the distribution block, and ground.

You might find no continuity and an open circuit of the block switch, showing that it is functioning normally, and find your light remains on when you pull the wire connector from the block terminal,... showing a faulty grounded circuit of the dash light.

Check these circuits and functions good,... those distribution blocks are tough, even after YEARS of sitting with "wet" rusty brake fluid!

[Old Man Powell]

Got the combination valve off and sure enough it was stuck. Cleaned and ready to go. Just waiting for my two remanufactured boosters to get delivered. Might as well put everything back together at once. My current boosters work but they have seen better days. Besides, everything else is new! I know it will never end but my "repair" list is finally getting a bit shorter.

[M & J]

 

[DRMousseau]

Glad ya solved it!
Was it stuck due to rust and particle accumulation??? Did it jus need flushing and cleaning out??? Or was it seized in some way?

[Old Man Powell]

Little bit of all of that!