Brake proportioning valve problem?

[vegiguy]

I've been trying to bleed the brakes on my '73 RR and can't get any fluid to go to the rear brakes. When I undo the fitting nothing is coming out the back port of the proportioning valve that goes to the rear brakes. Is something malfunctioning inside the valve, or is it just clogged up? Is there anything I can do to repair it, or is the valve not serviceable and has to be replaced? The car sat around for a number of years with the brake lines undone and no fluid in the MC if that makes any difference.

Thanks for any help.

 

[vegiguy]

I've been trying to bleed the brakes on my '73 RR and can't get any fluid to go to the rear brakes. When I undo the fitting nothing is coming out the back port of the proportioning valve that goes to the rear brakes. Is something malfunctioning inside the valve, or is it just clogged up? Is there anything I can do to repair it, or is the valve not serviceable and has to be replaced? The car sat around for a number of years with the brake lines undone and no fluid in the MC if that makes any difference.

Thanks for any help.

According to this post on the Chevy Talk forum I have a bad master cylinder: http://www.chevytalk.org/fusionbb/showtopic.php?tid/230240 . I reckon Mopars aren't any different than Chevies in this regard.

 

[69Runner]

In that link they discuss both the MC and proportioning block but never post the solution. Darn Chevy guys...

The fact your car sat as you described indicates it was subjected to its environment - hot/cold, damp/dry etc. The valve consists of spools, springs, checks and orifices. There is a possibility you could take it apart and clean it up, depending on how badly it is corroded or gunked up inside. Replacement might run around $50, not sure of your budget.

Question is, how confident are you in your ability to clean it up? What if you missed something, and your brakes did not work? That would always be a question in my mind, in the same situation.