Bad proportioning valve?
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Bad proportioning valve?
I posted a reply in a similar topic but didnt know if that was the right place to ask for help... so sorry for the duplicate... but I hope we can figure this out. 
This forum has helped me alot with a similar problem I am having.. I am working on an 87ish ford areostar van. I've got NO pressure to the rear brakes. the front one work fine, great in fact... but not a single drip to the rear.... I've taken apart the proportioning valve and cleaned it out(like new IMO) and put it back together the same way..... when I install it I still have great pressure to the front but not a drip again the to the rear.... whats goin on?
I've take off the rear line(disconected it from the proportioning valve on the bottom) and when my asst. pumps the breaks I'm getting only drips from the bottom of the valve.... if I do the same to the front line(on the valve) it squits like crazy..... why am I not getting pressure in the valve to counter that spring in there to get fluid to the rears?
Thanks in advance!
This forum has helped me alot with a similar problem I am having.. I am working on an 87ish ford areostar van. I've got NO pressure to the rear brakes. the front one work fine, great in fact... but not a single drip to the rear.... I've taken apart the proportioning valve and cleaned it out(like new IMO) and put it back together the same way..... when I install it I still have great pressure to the front but not a drip again the to the rear.... whats goin on?
I've take off the rear line(disconected it from the proportioning valve on the bottom) and when my asst. pumps the breaks I'm getting only drips from the bottom of the valve.... if I do the same to the front line(on the valve) it squits like crazy..... why am I not getting pressure in the valve to counter that spring in there to get fluid to the rears?
Thanks in advance!
Postmaster
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RABS unit has failed internally, closing off the rear circuit. (Failed solenoid). Here's a link to guy with a similar problem. Scroll down to #14 post and read from there. Its a Ranger in question but it is the same RABS valve for both vehicles.
https://www.ford-trucks.com/forums/2...t-in-here.html
https://www.ford-trucks.com/forums/2...t-in-here.html
Postmaster
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(on edit) I thought all Aerostars had RABS but I think you are correct. I just checked and RABS was first used on the Aerostar in 1990. I'll have to punt at this point and let one of the more knowledgeable guru's take over.
By the way, welcome to the Aerostar forum!
By the way, welcome to the Aerostar forum!
Last edited by aerocolorado; Dec 20, 2006 at 04:21 PM.
Post Fiend
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From: Washington state
check to make sure you have fluid output from front section of master cylinder which supplies pressure to rear brakes thru propor. valve....no fluid out= shot leaking front section of master cyl....replace unit
or
proportioning valve shuttle piston is propbably stuck to front brake side from corrosion or damage....or feed hole to rear brakes is plugged by debris....
replace combination/proportioning valve is best at this point
or
proportioning valve shuttle piston is propbably stuck to front brake side from corrosion or damage....or feed hole to rear brakes is plugged by debris....
replace combination/proportioning valve is best at this point
Last edited by 96_4wdr; Dec 20, 2006 at 07:34 PM.
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96_4wdr your my hero! OK, I pulled apart the Prop. valve and there IS a red cole-like-plug in there with a gasket... now I checked and there is GREAT flow from the front of the MC that feeds the rear break line. now I know for a fact that there is good flow into the prop. valve but nada comming out...
you had mentioned a "feed hole to the rear". I looked all around this cone inside(that has a tension/return spring with it) and I saw the hole in the front side of the cone, but no exit to it. I cleaned it out and checked again, but I don't see a hole for the fluid to go from inside the cone(shuttle piston?) to the back of it(sealed with a gasket)... am I missing something?
To me it appears that there is absoutally NO path for the fluid to get from the feeder hose(on top) to the line hose(in the rear). it would make sence now that there SHOULD be a pin hole or something.... if that was the case then I missed the hole(and didn't clean good enough).
is that all I'm missing is that hole? or is there something else goin on?
thanks again!
you had mentioned a "feed hole to the rear". I looked all around this cone inside(that has a tension/return spring with it) and I saw the hole in the front side of the cone, but no exit to it. I cleaned it out and checked again, but I don't see a hole for the fluid to go from inside the cone(shuttle piston?) to the back of it(sealed with a gasket)... am I missing something?
To me it appears that there is absoutally NO path for the fluid to get from the feeder hose(on top) to the line hose(in the rear). it would make sence now that there SHOULD be a pin hole or something.... if that was the case then I missed the hole(and didn't clean good enough).
is that all I'm missing is that hole? or is there something else goin on?
thanks again!
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Hi GrageNut
I'm guessing that everything was OK until you start bleeding the rear brakes.
The proportioning valve has a safety shuttle valve that's normally open to allow fluid to reach the rear brake line. When you have a catastrophic failure (leak) in the rear brakes, the valve is closed off to prevent fluid from reaching the rear line, just so you still have pressure on the front brakes and you don't lose all fluid.
When people bleed the rear brakes, they usually have soneone else pump the pedal several times and then open the rear brake bleed valve. Alas, this simulates exactly the condition the shuttle valve is designed to prevent, and it promptly closed up. that's why you don't see any more flow to the rear.
That's why this valve on the Aerostar is not exactly called a "proportioning valve," but a "combination valve" since it combines both functions in one body.
About the only thing you can do is to open up the proportioning valve and try to clean up everything, if it's not too badly corroded.
I'm guessing that everything was OK until you start bleeding the rear brakes.
The proportioning valve has a safety shuttle valve that's normally open to allow fluid to reach the rear brake line. When you have a catastrophic failure (leak) in the rear brakes, the valve is closed off to prevent fluid from reaching the rear line, just so you still have pressure on the front brakes and you don't lose all fluid.
When people bleed the rear brakes, they usually have soneone else pump the pedal several times and then open the rear brake bleed valve. Alas, this simulates exactly the condition the shuttle valve is designed to prevent, and it promptly closed up. that's why you don't see any more flow to the rear.
That's why this valve on the Aerostar is not exactly called a "proportioning valve," but a "combination valve" since it combines both functions in one body.
About the only thing you can do is to open up the proportioning valve and try to clean up everything, if it's not too badly corroded.
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Copper- I recieved the van in this condition, but yes, your describing how I tryed to fix it.... bleeding with a partner... I opened up the combination valve and took out the spring the gasket and the red cone deal(shuttle piston?) everything is in good working order.
So now the question becomes; When I put it all back together, do I put the piston ALL the way into the valve?(That seems to stop all fluid) or do I place it in there so there is a gap in the back of the valve to allow fluid to pass?
Then, how do I bleed this system? if I cant pump it? just open all 4 bleeder screws and let it sit for 5-10 mins?
Thanks again everyone!
So now the question becomes; When I put it all back together, do I put the piston ALL the way into the valve?(That seems to stop all fluid) or do I place it in there so there is a gap in the back of the valve to allow fluid to pass?
Then, how do I bleed this system? if I cant pump it? just open all 4 bleeder screws and let it sit for 5-10 mins?
Thanks again everyone!
Post Fiend
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From: Washington state
the shuttle piston has to be centered to pass fluid to front and rear brakes....if there is no or low fluid pressure on rear side piston will move that direction and shut off all flow leakage to rear....stops the loss of front brakes in cause of catostropic rear leak....same-same other direction
center the shuttle piston in comb/prop. valve....fill fluid reservior on mc....i flush and bleed my brakes all by myself using a rubber hose over bleeder screw **** into partially filled can of brake fluid to prevent sucking back in air.....i pump up the brakes... crack bleeder until fluid flows...pump brakes gently several times only 1/2 way down....close bleeder and move to next wheel
secret is gentle slow brake pumping only half way down....knowledgable assistant helps....that leaves out most wives
RR, RF, LR then LF per Ford RABSII/ABS manual
probably RR, LR, RF, LF for non ABS
center the shuttle piston in comb/prop. valve....fill fluid reservior on mc....i flush and bleed my brakes all by myself using a rubber hose over bleeder screw **** into partially filled can of brake fluid to prevent sucking back in air.....i pump up the brakes... crack bleeder until fluid flows...pump brakes gently several times only 1/2 way down....close bleeder and move to next wheel
secret is gentle slow brake pumping only half way down....knowledgable assistant helps....that leaves out most wives
RR, RF, LR then LF per Ford RABSII/ABS manual
probably RR, LR, RF, LF for non ABS
Last edited by 96_4wdr; Dec 21, 2006 at 08:51 PM.
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ok, just to be clear...
when I disassemble the combo valve. I DONT push the shuttle piston all the way back.. I just place it in there and then put on the spring and cap right?
this makes alot of sence as when I push it to the back I can't get fluid to the rears...
Thanks so much 96_4wdr!
and the van is NONabs. so I agree that its RR,LR,RF,LF. as to do the longest to shortest lines..
Thanks again to everyone. I'm going to give it the old college try in the AM tomarrow. I'll let you know how it go's.
-Thanks all
-GrageNut
when I disassemble the combo valve. I DONT push the shuttle piston all the way back.. I just place it in there and then put on the spring and cap right?
this makes alot of sence as when I push it to the back I can't get fluid to the rears...
Thanks so much 96_4wdr!
and the van is NONabs. so I agree that its RR,LR,RF,LF. as to do the longest to shortest lines..
Thanks again to everyone. I'm going to give it the old college try in the AM tomarrow. I'll let you know how it go's.
-Thanks all
-GrageNut
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GrageNut,
If you have a VOM or DMM, you can check for the correct position of that shuttle valve. There is a screw-in sensor on the front of the MC that has a contact point that is designed to touch the shuttle valve if it is out of place. If this happens, it completes a circuit to ground. So you connect one probe of the DMM to ground, the other to the terminal of the sensor, and put the meter on continuity check or Ohm reading. If the valve is out of place enough to touch the sensor, you should see it on the meter. Normally, if the valve is positioned correctly, it will not touch the sensor.
If you have a VOM or DMM, you can check for the correct position of that shuttle valve. There is a screw-in sensor on the front of the MC that has a contact point that is designed to touch the shuttle valve if it is out of place. If this happens, it completes a circuit to ground. So you connect one probe of the DMM to ground, the other to the terminal of the sensor, and put the meter on continuity check or Ohm reading. If the valve is out of place enough to touch the sensor, you should see it on the meter. Normally, if the valve is positioned correctly, it will not touch the sensor.
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