Who knows about proportional valves?

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mopar56

mopar56

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Ok so because I know we need the facts this ISNT a A body, I'm working on my hot rod but the frame and brakes are a 81 D150 2wd, so it is 10 inch front disc brakes and rear drums, 10 inch again if I remember correctly with the factory proportional valve, and manual brakes, the master cyl is the only difference here as I used a pedal box from a 82 b150 , ( van) here is the issue, I bench bled the master cly the usual way dumping fluid from the outlets back into the resvoir ( plastic/ aluminum) then when I go to bleed the brakes, ( by myself using a vacuum style pump) the fluid flows fine to the calipers but nothing goes to the rear, I disconnected the line from the proportional valve to the rears and no fluid flows when I pump the pedal, I pulled on the reset button on the valve and tapped lightly with a hammer but when I push on pedal I get no fluid my next step I was going to try was completely bleeding the fronts and hooking the rear line back up and stepping on the brake pedal I have read this can reset the spool in the valve, I also tried some compressed air through the line coming from the master to the valve but I don't see fluid, this truck frame has not been on the road for years BUT I replaced all the wheel cyls , calipers, hoses, and lines, only the proportional valve is original and the b-van m/c is not new but seemed to bleed out ok. Ideas????
 
So the "peddle box" Danged Cannucks, is orphaned from the proportioning valve?
 
Yes the peddle box actually is a box hence why I chose it for the project, the 56 cab had pedals that went down into the floor which I could not use, the b-van uses a steel box to house the brake and in this case clutch pedals and yes the van did not have power brakes, like Rusty said the " miser" package in the early eightys came with manual brakes I actually bought one new in 82 318/4 spd o/d manual brakes and steering but I splurged the extra 125 bucks and upgraded to p/s lol, all though this got me thinking I don't know if the frame/ proportional valve I have was originally p/b or manual? Maybe it was power do you think the proportional valve would be different? Doubt that would effect bleeding though?
 
The only thing I can think of is that the rod length into the master cylinder in too long (deep) thus not including the rear brakes into the equation.
 
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ok so is this the Combination valve that you have?


upload_2021-7-12_1-55-30.jpeg


upload_2021-7-12_1-54-51.jpeg
 
If rear is locked out, then plug the rear port on combi valve and press pedal. It should reset it. When i say plug, i mean install an inverted flare plug. If it wont recenter this way, unbolt it and throw it in the lake.

many times i have bled brakes and tripped the valve,and by pressing pedal hard, it recenters.
I put a mid 70’s combi valve in my 51 Fargo and it seems to work fine.

i usually connect the switch,and bleed brakes with the key on so i know it hasnt tripped.
 
On Ford's IIRC there is no centering springs in the distro block / safety switch. To center the spool you turn the key to on and release pressure from one end or the other till the safety light goes out.
Might be similar on what you have?

On a side note the distro block should not prevent fluid from flowing to either end regardless of where the spool is inside of it.

On another side note, some newer cars use a cross pattern for the breaks, one front and one diagonal rear are on the same cir, don't know if that would have the effect you describe if they were not hooked up that way.

On a last side note, typical master cyl enders use the rear most piston to push on fluid that then pushes on the front cyl. Since the front brakes work but the rears do not, perhaps you have an air bubble between the two in the MC? Technically with enough travel of the rear most piston it will contact the front most piston and apply pressure to the rear brakes. Sort of what Bodyperson was pointing to.
 
mopar56 said:
I pulled on the reset button on the valve
Click to expand...
Post a photo of this valve (or go look in the FSM for the truck it came from)
To the best of my knowledge.
Proportioning valves do not have buttons on them. There is no need for a button,
Metering valves sometimes do have buttons on them. These make it easier to bleed although not always required when using the pedal method.

There are combination valves on many vehicles that incorporate all functions into one casting.

Chrysler explains the metering valve here and the next page.
 
mopar56 said:
Weird when I go to upload photos I keep getting a error message maybe a recent phone update for security or maybe a site problem I'll try again later.
Click to expand...
I resize photo to large, been like that for a while.
 
Ok I think o got things moving at least, so my son has a 80 s/b dodge so same frame/brakes I got him to send me photos of the valve to compare and it was the same, then I bled the front brakes first and stomped on the pedal several times, oh also my new one man brake bleeder showed up from Amazon today to so I used that and it had way more suction, I was then able to get fluid at all four corners, my pedal feels semi firm but there is still air in the system so I figure I'll just get one of my sons over to apply firm pressure to the pedal to force out the rest of the air but for now I tried one more trick, I have opened the r/r bleeder and left a hose on it in a pan to see if it will gravity bleed I'll check it before I go to bed and see if it's moving, if not I'll just bleed it with one of the boys then hopefully done. We'll I'm on the subject though any one have an idea what to hook the wire on the proportional valve to? There is a red light on the dash of this old truck I could use I am assuming it works like a oil pressure unit so it grounds?
 
The switch on valve grounds when its tripped. Pos to lamp,neg to switch.
 
Ok thanks tooljunkie that's kind of how I thought it worked so I will hook it up that way, the bulb in my dash is grounded to the body through the metal dash board I'll just swap out the bulb pigtail for a two wire and hook to the ground to the switch. BTW, gravity did not bleed the r/r after sitting all night so I'll just finish up the old fashioned way! Thanks again to all who helped here lots of good ideas as usual!
 
Rick Ehrenberg has an Ebay store that sells all the good parts needed for swaps/upgrades for projects like this. If you don't know who he is, look him up.
 
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