I'm seriously considering eliminating the proportioning valve in my 1982 F100. Right now the valve is froze and is causing only rear brakes to work. I've done everything short of removing the valve itself and disassembling and repairing it. It's definitely the proportioning valve. I've now replaced the master cylinder 3 times and bled the system over and over again (I've got a mity mite). All with the exact same results.

Apparently these are not very easy to come by, so I'd rather just delete it and put a manual metering valve on the rear brakes and run straight from the master cylinder to a tee for the front.

Has anyone done this and if so, what did you go with? Any other suggestions short of going to a junkyard, hoping to find the same proportioning valve and rebuilding that one hoping to even rebuild it right?

 

Fixing the problem as opposed to modifying a safety system would be preferable. You already spelled out the logical course of action. Only thing I can suggest is it is not a failure prone part. A used one should be fine.

 

Ya really need it....
New ones are out there.

 

Try calling [url]http://piratejack.net/[url] to see if they can help with a valve or a kit to fix what you have now.


If they don't have something I am sure they can tell you if what you want to do will work.
Dave ----

 

Really? Where?

 

I don't live in an area where junkyards are prevalent, let alone ones that have early 80's 2wd trucks. Trust me, I've checked around for other parts..

Any suggestions for replacements? I'm up for that, but finding another one is probably out of the question for me.

 

Summit Racing shows 147 results in a search, e.g. Classic Performance Brake Proportioning Valves PV-2 - Free Shipping on Orders Over $99 at Summit Racing
I have no idea if that's the specific one you need, just showing it as an example).

 

It doesn't look anything like the one in my truck. Actually I've not been able to find anything new or rebuilt that looks like it. I was really hoping that there was someone on this forum that had found a direct replacement. I'm not against disassembling and replacing o-rings, etc. I just figured there's got to be something out there that will work.

I've read a lot of the posts on here about that valve, and from what I've read, there are many types, even between the 80-86 and different ford trucks of that era. Also from what I've read, these were really not made to be serviceable. Even getting a replacement to work, it may not be the proper pressure differential for the rear. Even if I was to rebuild it, there are no rebuild kits, and no information as to what size the o-rings are, or replacement parts for anything that is broke.

So the safety factor of the proportioning valve is that if a leak happens on say the front, then the valve moves to block flow on the front so you still have braking on the rear, and vice versa. Since my truck has a master cylinder that has 2 reservoirs, larger for the front, and smaller for the rear, then wouldn't that still provide the same level of protection since the front and rear are separate? Giving the same scenario with the front developing a leak, the rear's would be completely unaffected by the leak on the front since the master cylinder has a separate reservoir and output to the rear brakes?

These are the reasons why I'd rather just put in an adjustable proportioning valve on the rears, and tee the fronts. I could understand the safety aspect if the master cylinder had 1 reservoir that fed the fronts and the rears.

 

Here's a pic of mine. BTW: I removed the switch to test it so that's why it's missing. It's back on now...





F100 2wd brake proportioning valve

 

This is a common fallacy and is NOT true... the BS that gets spread on the Internet irritates me sometimes but there's not much I can do about it.

A really good guy I know in the 73-79 forum by the name of fmc400 said it best:

His name is Jeff and he disappeared a year or so ago, kinda like Ralph did - just vanished.

But that valve by itself - and barring any crud in the system - cannot shut off the flow to one or the other circuit:



~~

According to the factory service manual, there are two primary types of those things used as shown in the picture from the service manual above.

Yeah, the things are hard to find and they're generally not inexpensive when you do find one. I took one apart once and reassembled it with the same parts since nothing seemed obviously in bad shape; I haven't tried to use it, though, I have it as a spare (or backup).

~~

You might read this:

https://www.ford-trucks.com/forums/1...l#post15658350

Or do a search on "differential valve" (with quotes) of the 73-79 forum, there are some good nuggets in there...

 

Thanks for the read Ctubutis! Mine is in figure 5 in the manual pic you posted.

This has got me curious. If it does not cut any flow off, then what could be causing the rears to lock up before the fronts? I've now tried 3 master cylinders and have bled and re-bled the brakes so many times I can't even count now.

Could the front metering valve be stuck and causing the issue? Weird thing is, when I've bled the front brakes, I get fluid. I'm guessing it's working correctly.

Another dumb question. If I do not have the bleeder rod pulled when I bleed the front brakes, will they not bleed? Should I not get any fluid since the front metering valve should block the flow? That may be what I'm doing wrong... not having the bleeder rod pulled..

I'm using a vacuum type brake bleeder system like a mighty vac.

 

I don't know the answers to your questions on that rod, but my recollection is that thing is only for aligning of the device that actuates the switch and has nothing to do with actual brake fluid flow to the wheels.

As for why the rear wheels lock up, incorrect assembly and adjustment of the drum brakes can cause that, as can grease or oil or hydraulic fluid on the brake shoes.

 

Here's my theory.. Take it with a grain of salt..

In various threads, including the one you posted, theres information from users and the manual that states in order to properly bleed the front brakes, the rod must be pulled out (for 1982 F100 2wd) in order to properly bleed the front brakes. I'm guessing that since I am not doing that, air is somehow being trapped in the inlet line from the master cylinder for the front brakes, but since I'm using a vacuum tool to bleed them, it is allowing some fluid to pass the front metering valve. Since the front metering valve is staying mostly closed, the fluid is heavier than air and the inlet line is higher than the proportioning valve itself, the air is not passing by the metering valve and going through the rest of the line to be ejected out the bleeder. Since the air is staying in the inlet line prior to the proportioning valve, the rear would have higher pressure causing the light to stay on and the proportioning valve slide to stay towards the front since air is compressible.

If I had someone pressing the pedal to bleed the system, everything may have been fine since the pressure would open the front metering valve, but since I'm using a vacuum, it's only sucking the fluid past it and leaving the air bubbles inside the inlet line to the proportioning valve. So maybe my proportioning valve is actually good and I'm just bleeding the front brakes the wrong way.. Hmmm...

It's a thought..

 

I suspect that the purpose of the tool is not so that you can bleed the brakes, but so that you can bleed them without activating the warning light and then having to reset it.

What I don't really understand is the purpose of the warning light. If you loose one circuit you're definitely going to know it because your braking effectiveness is going to be very reduced.

I just checked summit and searching for "brake proportioning valve" then filtering by yeah comes up with zero for Bullnose Fords.

 

I have never pulled any type of pin on the proportioning valve to bleed the brakes.

Right now I am running my 89 with no proportioning valve, just straight to the master cylinder. There is a reason; You can't find the proper proportioning valve for your truck, my 89 didn't even come with one.

Sometime after 86 Ford or Bendix or both came up with the RABS system(rear anti-lock brake system). Instead of the proportioning valve, they use a speed sensor in the rear axle, a circuit board, and a valve in the rear line. It's supposed to modulate the rear brakes if they start locking up. Like everything else it develops problems, and there is not much aftermarket support for these old systems, or it's very expensive to fix it. This system is famous for giving a spongy pedal.

So for now I have bypassed the valve, so that effectively makes my rear line run straight from the master to the rear brakes, and the front line goes from the master to a tee and then to the front brakes(as it originally did).

I will tell you it will and can lock the rear wheels up when you hit the brakes hard. Of course it's going to on a empty pickup with no weight in the back. If you could somehow find a proportioning valve, I would. You could try one of those adjustable valves like the racers use.