I think I may need to replace the brake proportioning valve on my 1973 Duster. It has front disk brakes, rear 10" drums and it has a booster on the master cylinder. I replaced every component of the brakes (because it was all totally shot) except for the steel lines and the proportioning valve. When I try to bleed the rear brakes, I get no air or fluid and the pedal does not move downward when opening the bleeder. Also the brake light remains on. Is there some way to bust the valve loose or does someone know where I can obtain a new one. I would do the junkyard route but I am afraid that those types of parts typically are shot too. Any ideas??? Can I remove the lines from the valve and somehow "bleed" them? Thanks.

Mike

All of the one's after 1974 are pretty nice and standard. I've seen some tech references to the prop valve previously having a plunger on the end to manually open it up during bleeding. Not sure what the part is called, I've never seen a prop valve like that. It's supposed to have a metal clip on the end to lock it open during the bleed down....


???

-D.Idiot

I looked earlier to see if there was a bleeder valve or something I could open. Of course, it is in an awful position where it is hard to see and almost impossible to reach. It does look like there is one area between a couple lines that looks like some kind of clip or something. I thought about disconnecting the lines at the valve too but couldn't figure how to do that without causing more problems like more air. I'll look more closely later when I get back. Thanks.

Mike

I would suspect that the hard line running to the back is rusted shut, and/or the hard lines on the axle are rusted shut or the rubber line is blocked. They do that after 30 years...

I had already replaced the rubber lines. Should I disconnect the steel lines at both ends and see if I can blow air through it? I would also add that the fronts do get fluid through them and the front disks are tight on the rotor which is why I suspected the valve. However, if the rear line is blocked, would that also trigger the valve? Thanks.

Mike

Yes, disconnect the hard lines and see if you can blow thru them. I have found that the sliding calibers have a tendency to stick if they are not used regularly.

Well, I cannot remove the rear line at the proportioning valve. I tried a tubing wrench and even it slipped but the fitting won't budge. I tried a small vice grips too but still no luck. I may just bring it to someone else to do even though that would cause severe damage to my pride. Any pointers? Thanks.

Mike

Try holding the old valve with something like a crescent wrench to stabilize it.

Then grab the fitting with your small vice grips and break it loose.

You will need to replace the fitting after you use vice grips on it. This may be a good time to replace the entire line. They aren’t much more than buying the fittings individually.

John

Don´t remove the prop valve yet, your switch piston may be off center.
Go to http://www.imperialclub.com/Repair/Lit/ ... /index.htm , it's a very complete article on power brakes. See page 10 Disc Brake Hydraulic System Control Valves to try to solve your problem.
Pay special attention to "Pressure Resets Switch Piston" and "Hold Metering Stem Out" paragraphs on page 12.
Hope this helps
Rafa

Well, that web site was down for several days. I finally got on and it is a great site. Thanks. Unfortunately, my proportioning valve is the old brass one that the manual at that site claims should automatically reset itself. So, back to trying to remove it I guess.

Mike

I'll be doing the same thing on my 80Volare soon, the back brakes lock up WAY to easy (in the rain trying to stop for a red light = SLIDE ) i'm going to be getting a fully adjustable one (universal) from Bayer or another brake company, i've seen them and they truely are amazing, but expensive...

Justin

Hey, Justin, on your rear lockup problem, make sure that the shoes aren't contaminated--- 90 wt or brake fluid from leakage, even though it may be dry now, they may have leaked before and whoever fixed the leak, tried to "get them by"... if the 90 wt or brake fluid is on or in the linings, its too late. Change 'em! I have also gotten a bad set of shoes to cause a lockup before, changed to a good grade of Raybestos or a Wagner (NOT ECONO GRADE!) and problem gone. Some of the "house brands" are real questionable. I also had a problem on my last Diplomat, the pedal would be rock hard and not go down much, but not hard like it would be with a bad booster diafram, rather, the pedal would creak and bind, and if I put all I had into it the pedal would get past this "hard spot" and then the backs would lock instantly... I replaced the booster 1st off, thinking that there may be a mechanical bind in it somewhere. Problem wound up being the prop valve.
I have seen where the primary and secondary rear shoes were either reversed or both pri on 1 side and both sec. in the other side cause that.
Check the backing plates to see how grooved they are if the shoes are getting hung up that will cause it, too. One more check; If 1 side of the wheel cylinder is seized and all the pressure is to 1 side of the WC, that can drive you nuts, too. Your car is pretty much stock as far as suspension, brakes, etc., right? Unless it has been modified for like autocross, drag race, etc, I don't know that I like the idea of an adjustable prop valve.
Did you ever get that 4 speed tunnel and check on the lower section of that driver's quarter off that one that you scrapped out?? I am still waiting! Did you get my last 2 e mails? I had to change my user name here with the board, since I "officially" registered, it won't let me on as Donram360 any more, it tells me that someone else already has that name. Yea, I know.... ME! Lemme know on those volare body parts.
Too bad we live so far apart, I could help you wonders on those brakes,
but Canada is a little far from Chicago. I will try to help you as much as I can thru the board or via E mail as much as I can, but without being able to actually see the car, its haed at best.

After travels and working on other areas of the car, I am back to trying to get brake fluid to the rears. I unscrewed the "Cap" at the bottom of the valve and was able to move the valve itself in and out so it probably isn't in the valve. I am still unable to disconnect the rear line at the valve. I have tried everything short of C-4 explosives and I want to disconnect it without trashing the valve. What do you think about this idea?....What if I build a pressure bleeder and disconnect the rear line at the differential (it does come off). Then perhaps the pressure bleeder can force fluid to the rear and "flush" out the lines. Is that something that might work? Thanks all.

Mike

When faced with a problem like this you just have to be systematic in your approach. Disconnect both lines at the MC to see if you have pressure and fluid there. If so, move to the next junction point and check again. Move through the entire system and check pressure and volume. I guarantee that eventually you'll figure out where the failure is.

Actually, I get fluid all the way to the front brakes and I get fluid at the MC for the rears but none to the wheel cylinders. I am unable to remove the lines from the proportioning valve to check there. Since that is the only place in between, it has to be the valve (which I doubt because the valve rod moves). So, it must be the line from the MC to the valve or the rear line. That was why I was considering pressurizing the rear line to perhaps move the fluid or dislodge any obstruction. I don't want to trash the lines or the valve. Thanks for any advice.

Mike