Hey guys. 79 F150 2wd 351M auto. I have replaced the master cylinder and am bleeding my brakes. I just checked the proportioning valve (I think I have to pull the pin out). When I got under there it was already out. I am able to pull it out and push it in and it does not return on it's own to either position. Is that wrong?

I started this a week or two ago (see this thread: https://www.ford-trucks.com/forums/1...inder-bad.html).

When I was bleeding the front brakes we lost all pressure. I assumed it was the m/c but now I am wondering if we blew the proportioning valve? I did not remember to pull the pin out when bleeding that time.

Here is what it looked like when I first checked it:


And here after pushing it in:

 

Mine does that too. I've been meaning to put a zip-tie or something around it to keep it in. I think it does affect braking when the button moves outward.

 

should just replace it with a new one. To my understanding that is a Safety device so that if you loose pressure to either front or back brakes it will trip to keep fluid from go-in to the system that is effected so you don't loose all the brake fluid. Then thats supposed to turn on the brake warning light in the dash.

 

Thanks guys. I pulled the pin out and bled as per normal. Pushed the pin back in and all seems to be operating as it should. Have driven it 15-20 miles using lots of braking. Spongyness is gone from the pedal and it stops well.

 

There are 3 functions contained within that cast iron Kelsey-Hayes brake valve assembly: Metering (hold-off) to the front disc brake circuit, Pressure Differential sensing between the front and rear brake circuits and Proportioning to the rear drum brake curcuit.



The end you're dealing with (Metering) has nothing to do with the proportioning function of the valve. It deals with the hold-off to the front brakes. On a cast iron K-H brake valve, on a truck under 6900# GVW, the metering valve pin is supposed to be pulled outwards while bleeding the front brakes.

On an F250/F350, with a Weatherhead brass brake valve body and a GVW of 6900# or greater, the pin is pushed inwards when bleeding the front brakes.

If there's a problem with the metering valve staying open all the time, it just means there's not going to be any delay of the pressure being applied to the front discs, before the rear brakes have time to build enough pressure to begin overcoming the spring tension of the retracting springs and moving the brake shoes towards the friction surfaces of the rear drums.

The purpose of the hold-off (metering valve) is to delay initial pressure from being applied to the front discs to give the rear drums time to overcome the retracting springs. It's designed to time the brakes so that all four brakes essentially begin to apply at the same time.

Disc calipers respond instantly to the application of the brake pedal. Drum brakes have to overcome mechanical means before the shoes come in contact with the drums.

 

Just taking comfort in the fact that mine wasnt the only one that looked that nasty .... The entire front drivers side of my truck has a fine layer of power steering fluid coating it.... I call it the desert protection package, Ford was way ahead of the times

 

Everything under my truck looks nasty it is a blessing and a curse. But mostly a blessing. My truck was a farm truck and the OP did what a lot of farmers do - he sprayed waste oil on everything under the truck, every year. It kept it from rotting away but makes it awfully messy to work under. Replacing the gas tank earlier this year was a special treat!

 

Thanks, UltraRanger. For now my primary goal is to get the truck ready for winter storage. I'll look at picking up a new (reman?) valve over the winter. Aftermarket ones I assume?