proportion valve for my truck

[snakebite8]

I am hoping someone has a spare proportion valve they can sell me.  I tried fixing my old one.  still wont work.  bought two from amazon and they both did not work.  the rear brakes wont bleed.  only thing stopping me from driving the truck is this.  hoping someone has one.  thanks truck is 1985 2wd

[Gary Lewis]

There were several of those valves, as shown on the page at Documentation/Driveline/Brakes and on the Proportioning Valve tab.  The one you want should be the 1984 and later one for the F150.

[snakebite8]

I can only find universal ones.  nothing that is 100% 1985 f150 ones.   and the two universal ones did buy did not work and the seller said they would.  

[Gary Lewis]

What doesn't work about them?  I ask because I wonder if your problem is elsewhere.

[85lebaront2]

Unfortunately, the only one I have is the one from Darth. According to the list it should be E4TZ-2B257-C which is not the one you need, that would be E4TZ-2B257-A

[snakebite8]

rear brakes wont bleed.   first new one only passenger rear would.  and 2nd new one both rear would not bleed.

[Gary Lewis]

snakebite8 wrote

rear brakes wont bleed.   first new one only passenger rear would.  and 2nd new one both rear would not bleed.

That's exactly why I asked.  The proportioning valve cannot differentiate between the left and right rear brakes.  There's one line that comes off the master cylinder and goes to the rear, where it splits at the axle vent on the axle, which you can see in the illustration below.

So if you were able to bleed one rear brake and not the other it isn't the proportioning valve's fault.  I'm going to guess that you may have a flattened brake line somewhere.  Maybe along the frame or on the rear axle.  Or, that the rubber hose that connects from the frame to the rear axle is bad.  I've heard about them causing similar problems.

[Steve83]

Gary Lewis wrote

The proportioning valve cannot differentiate between the left and right rear brakes.

I agree.

Gary Lewis wrote

There's one line that comes off the master cylinder and goes to the rear, where it splits at the axle vent on the axle, which you can see in the illustration below.

So if you were able to bleed one rear brake and not the other it isn't the proportioning valve's fault.  I'm going to guess that you may have a flattened brake line somewhere.  Maybe along the frame or on the rear axle.  Or, that the rubber hose that connects from the frame to the rear axle is bad.

For the same reasons that the prop.valve can't cause a L/R bias, neither can the frame tube or rear axle hose.  The fault MUST be between the splitter block on the axle vent, and the problem wheel cylinder.



But if anyone actually needs one, I still have this one that worked fine when I switched to the later system:

[Gary Lewis]

Steve - I fully agree that the frame line nor the hose can cause a problem with one brake and not the other.  But, I wondered if there was something odd going on that might have gotten overlooked since usually he seems to be unable to bleed either rear brake.  Perhaps the time he could bleed the passenger's side was a fluke?

[snakebite8]

also no brake fluid is leaving the valve to go to the rear

[Gary Lewis]

snakebite8 wrote

also no brake fluid is leaving the valve to go to the rear

I'm confused.  Were you able to bleed the right rear with one of the valves?  If so, brake fluid has to have been coming out of that valve then.

Do you still have that valve?  If so, put it back on as it is good.  Then we can troubleshoot why the driver's side wouldn't bleed.

[snakebite8]

the old one valve.  front brakes will bleed.  the rear part of the valve.  nothing is coming out of it.  I loosened the line to see if any brake fluid is coming out.  and it was dry.  

[Gary Lewis]

Yes, but you said that one valve you tried did allow you to bleed the right rear wheel.  Do you still have that valve?

[snakebite8]

No. I returned that one.

[Gary Lewis]

Then I suggest you contact Steve83 to see about buying his valve.

[ArdWrknTrk]

The combination valve is meant to shut off fluid flow if the internal shuttle shifts all the way over and sets a fault light.
But they get sticky and don't return to center.

Somewhere on FTE is a cross section drawing showing the seals (o-rings) and springs inside.

Maybe you should try back bleeding, pumping fluid from the bleeder to the reservoir.
I don't know if you can develop enough pressure to push the shuttle back by hand, but it's worth a try.
I've done it before with my Silverline Mity-Vac bleeder hooked up for pressure instead of suction.

[Steve83]

ArdWrknTrk wrote

The combination valve is meant to shut off fluid flow if the internal shuttle shifts all the way over and sets a fault light.

Mine never functioned that way - it allowed the leaking side to continue draining fluid until that part of the MC reservoir was empty.




On a few occasions...   I've never read anything that said it should stop flow under any circumstances when working correctly.

ArdWrknTrk wrote

But they get sticky and don't return to center.

According to Haynes, and the way mine always worked, they never self-center.  Once the leak is fixed, the OTHER side has to be bled (an intentional leak) to move the piston back that way, and stopped when it reaches center (light off).

ArdWrknTrk wrote

...a cross section drawing showing the seals (o-rings) and springs inside.

Haynes has that, too.


BTW
I took this when I was disassembling that truck, just before swapping to the '93 frame & body:

[ArdWrknTrk]

Well, by looking at that Haynes drawing *I think* you should be able to tell that if the spring centered shuttle shifts over far enough for the spring loaded switch's pin to drop into the shuttle groove (setting off the light) that the position of the O-rings preclude the flow of brake fluid to that side.
At least that's what the Ford cutaway shows me.

The switch plunger has to be pulled out (on 150's) or pushed in (certain years of 250-350) for the centering springs to reset the shuttle.

Like brake fluid does if it's left to sit, the bores will get sludged up and coated.
The shuttle will become sticky, and not travel fully over, to where it will set a light.
But it also will not return to center if spring pressure can't overcome stiction.
And if the 35 year old seals are shot they may not 100% keep fluid from weeping past.

Edit: I think (your drawing should be the same)

I'll gladly admit I'm wrong if you prove otherwise, and I'm not looking for any arguments.
Show what you know. I'm man enough to accept that I cannot be perfect.

[ArdWrknTrk]

ArdWrknTrk wrote

The switch plunger has to be pulled out (on 150's) or pushed in (certain years of 250-350) for the centering springs to reset the shuttle.

This is why procedure should show that the plunger needs to be held out (or in) for any brake bleeding aside
from while working on an already full system.

[Gary Lewis]

Oddly enough, I found a post on FTE between two guys that were in my house 10 days ago.  Start with Jim/ArdWrknTrk's post from 8 years ago and read down.  You'll get to Scott/Kramttocs' post and then Chris/ctubutis' posts.