I recently replaced the drum brakes on my car with a complete used front drum system from a 1969 mach one. I used the dist distribution block and the proportioning valve from the 69. The brakes work great and the system doesnt leak, but the warning light is on and wont go out. I used the procedure from my shop manual for equalizing the pressure and it doesnt work. My mechanic suggests that rebuilding the porportionig valve might solve this. will this work or do you think the dist block may have to be rebuilt also. and is this even possible? does anyone know how to rebuild these parts or of a shop in norcal than will do it?
Thanks,
Kip

 

That valve is called a combination valve and is a real PITA to center. I don't think it's re-build-able. If you can't truly get it to center, replace it. Back in the day we used to take the light switch out and put an indexing pin in it to keep it centered, the valve is designed to move to the side that has lower fluid pressure which moves the shuttle and grounds out the light circuit.

 

What do you mean by "Back in the day we used to take the light switch out and put an indexing pin in it to keep it centered"? can you explain the procedure and what will it accomplish? As for replacing it I don't know how possible that is because they dont make em anymore.

 

I think I unplugged the connector with no ill effects.

 

thats what I am doing now, but I just like the idea of having it work.

 

I don't really know what it does...

 

You can unplug the connector if you don't want the light to work. I was a certified auto tech back in the 70-80s when these cars were really out there. What I mean by my comments is we would physically remove the switch out of the block and insert a special service tool in its place to keep the valve shuttle centered. while we service the hyd system. I think you can still buy those tools.

 

It is a warning light that advises the driver that ONE circuit of the brake system has FAILED and requires inspection.


The easy way to recenter it is with 2 people.

1) One pushing the brake pedal

2)while one slightly opens the flare nut on the PPV (on the circuit that didn't leak) to allow the valve to go the opposite direction..and centering..shutting the light off waiting for the next failure

Sometimes pressing really hard on the pedal will center it as well

 

I used the stomp method my self

 

cool thanks. Ill try the stomp method. then the physically centering it with a pin or something. Ill take it apart and look at it to see what will work.