Have a 79 f350 super cab, rear wheel drive. The truck sat for about ten years and I've slowly been working on it slowly over the last year, just put it on the road last month and never had any problems with the front brakes locking up driving around the yard, take the truck for the first real road drive and 5 minutes in the front brakes lock up, thought the calipers might be seizing and decided to go ahead and pit new rotors, pads, calipers and rubber hoses up front, hard lines are in good condition so i left them alone, same thing 5 minutes in front brakes lock up, so i start thinking maybe it's the master cylinder, replace that, same thing, pedal is hard as a rock and doesnt want to move much further towards the floor,when i start the truck the pedal does sink so i believe the booster is working sometimes, also i have one of the old kelsey hayes brake controllers that is plumbed to rear brakes side of the master cylinder and that is showing that the rear brakes are being applied while i am having the severe front tire lock up,im running out of ideas, anybody have any thoughts as to where my problem could be

 

I had the same thing happen to me a few years ago on a '79 after doing the front brakes. I ended up doing the rears and the problem went away, I don't know what or why. If it sat 10 years, pump out all the old fluid and start fresh.

As a side note, the previous owner had reinstalled all of the left rear brake stuff on the right rear side and all of the right rear stuff on the left rear side, so double check everything as it should be. One big problem that we all run into is putting things back "the way it was".

 

Did you push in the metering valve thing on the proportioning valve block, when you bled them?

 

If the rear wheel cylinders are frozen could cause similar issues as only front brakes would be working an can cause them to lock tighter , since these trucks are pre anti lock . After ten years the proportional valve could also be stuck an only letting front work an don't rule out that the old kelsey hayes brake controller may be stuck an not working right an really not giving enough pressure to rear brakes

 

No i did not push in the metering valve when i bled them, can you please explain so i can understand how that works and will help me

 

Thank you for the input, just to clarify when i mean the brakes lock up, the front brakes stay on even when i let off the pedal, the pedal doesnt fully retract, and the truck wont move out of its own way unless in lo or reverse

 

Scroll to the bottom of this post:
https://www.ford-trucks.com/forums/1...l#post14696861
Check out the illustrations of the two different valve blocks.

Basically you need to actuate that valve, when bleeding the front brakes, by pushing it in on the heavier trucks like your F350, and pulling it out on the lighter trucks like my F150.
And be careful around the Brake Warning Lamp Switch which threads into the valve block. They are plastic and will break easily.
Did you find it difficult to impossible to get any fluid out of your front bleeders?
Also definitely check your rear wheel cylinders. Mine both had their rear pistons seized in the bore. I'm pretty sure my truck sat for at least the first ten years of this century...

But it does sound like you're more than halfway home when it comes to redoing your brakes.