Proportion Valve Blues

[Bruno2]

I need to do this on my 96. I had an issue a few years ago where it was keeping the pressure on my rear drums after the pedal was released. I took the valve off and cleaned it. A new valve is like $280.00. That kept the brakes from locking down like they did before. However, I have eternal ABS light on. Seems like the ABS isnt working either. I did after extensive searching on the web find a tutorial on how to rebuild them, but it wasnt my valve in the tutorial.

[Gary Lewis]

This probably isn't your problem now that you have gotten the brakes to release, but there's an adjustment on the pushrod between the booster and the master.  If you make that too long the brakes can't fully release.

Scott, the welder guy, and I found that out the hard way recently.  He came over with his '78 with brake prob's.  After bleeding and adjusting the rears we still had no pedal, so adjusted that rod.  It made all the difference in the world, but the brakes wouldn't release fully.  Backing the screw off slightly fixed it.

[Bruno2]

Does the master need to come off to do this?

[Gary Lewis]

Jein - German slang for yes and no.  Pull the two bolts holding the master to the booster and tilt the master forward and a bit to the side.  You'll see the pushrod.

The factory manual gives a precise length the rod should be and warns that if it is too long the brakes won't disengage.  And, it shows how to make a U-shaped gauge to measure it, which is otherwise very difficult to do.  We guestimated it and got it wrong, so Scott said he knows someone with a laser cutting system and was going to ask him to make that tool.

[Bruno2]

This is my "ABS" light though. Is it the same issue?

[Gary Lewis]

Maybe not.  I don't know what causes the ABS light to come on.  This issue causes one side of the brake system to keep some pressure in the system.  So, would that turn the ABS light on?