Thanks. I already tried the bleeder screw earlier when locked up. What is the procedure to check the proportion valve. My buddy and I suspected that could be it. Sandy Edit In reading about the valve it seems that it really only applies to the rear wheels and anti-lock brakes which are not my issue. Or am I wrong?

 

No, the prop valve can definitely effect the front brakes. This happened to a customer with a new prop valve last year in fact. I mentioned it because of that experience, but said that it's not as likely on an original as it is on the new (crappy) ones that I'm aware of.
In my case ('79 F350) my prop valve is blocking fluid to the front brakes and all my braking is done on the rears. At least I believe it to be the prop valve as that's the last thing I have not replaced.

The reason it can drag is that your front brake lines also go through it. It's called a combination valve too, because it not only lowers pressure to the rear, but acts as a distribution block for both front and rear lines, and houses the imbalance switch to turn a light on in the dash should there be a leak.
But most important for our discussion here I believe, is the "delay valve" component of the front system. Visibly, it's just a metal tip sticking out of a rubber boot. Inside it's a spring loaded valve that delays application of the front brakes for just a moment while the rear brakes start slowing things down first.
This function serves two parts. It allows the rear brakes to take up any additional slack that they might have (if they're out of adjustment for example) but mainly improves stability in a panic stop. Think of how you use trailer brakes alone if a towed load gets squirrelly. Same thing happens when the rears are allowed to apply first and harder for just a moment.

This valve "could" conceivably be plugging up the port and not allowing the pressure to bleed back into the system. Not really sure if this is what's causing yours. But it's one possible scenario.

You could find the metal tip, pull it or push it against the spring pressure and see if that releases the pressure. In the old days Ford used the type that you pulled on for the F150's and Broncos, and a type that you pushed on for the F250's and 350's. So not sure what you might have on yours.
And speaking of which.... Part of the bleeding process is actually to manipulate that valve during the bleeding process. We tend to forget that (or don't know of it in the first place) sometimes with the newer vehicles. I'm always on about it with the old seventies vintage trucks, but never even thought about that with yours or others with newer trucks and brake bleeding questions here on the forum.
For all I know it's not longer even part of the process? Don't remember reading about it in the newer truck manuals. Maybe someone else following this discussion can chime in on that aspect and clear it up for us.

And one last thought. Unfortunately, I don't believe you can rule out the new hoses 100% anymore. Used to be you could count on a new part being good. Apparently not any more, and I know of some members that have had brand new brake hoses be no good and somehow block pressure. Mostly from being applied to the brakes in the first place, but it wouldn't take much of a segué to believe that they could block pressure from releasing.
The good news (sort of) is that it's very unlikely that both hoses would be pooched and causing both calipers to stick. If this is happening to both wheels then, I would have to say that points more to the rest of the system upstream from them.
Do both of your calipers seem to be equally tight?

Paul

 

Yes they are both tight. Is the rabs unit what is called the proportion valve? My info shows it to be. And then there is a valve that just looks like a big bolt they call the Master cylinder proportion valve and it is suppose to be between the master cylinder and the rabs. Which one am I looking for to check it?

 

Showing my ignorance, but I'm not sure what a RABS is. Sounds like something "....anti-lock brake system", but could be "radius arm brake supercharger" for all I know!

Thanks

Paul

 

Ahh, probably "rear anti-lock brake system" maybe?

Paul

 

Got a pic (or a link to a page) showing the two devices? Yes, the master cylinder proportioning valve is what I'm talking about.
But it sounds as if, with anti-lock braking, the old delay valve device might be completely unnecessary and no longer in use.

Paul

 

In looking at my system, I think the Master proportion valve is factory installed on the side of my Master cylinder. My two front brake lines do not go to the RABS. They go straight to the master cylinder. So that should rule all that out right? After thinking more about it the only thing I can see to cause my issue at this point is the brake line between the two front calipers since the rubber ones were replaced and the other thing is the brake booster/ booster rod. Could there be anything else?

 

If the pushrod from the booster is up against the master when it shouldn't be, unbolting the master from the booster (leaving the lines connected) should release the brakes. If the brakes stay locked up when the pushrod isn't touching the piston in the master, then you can rule out the pushrod length.

Good luck. I hate working on brakes.

 

I know the above post are lengthy but lots of variables. Anyway, I did what you said earlier in a post, Didn't release. I agree with you about working on them, especially the drums. Got another idea? Thanks Sandy

 

I did NOT read every post. But,you have to be pulling your hair out by now! What about checking your system out like an electrical system? Start at the ends and work down stream. Start MC unbolt it from vac booster. No help? Pull hose off MC and so on..... The size of this task is TRULY determined by the amount of rust rot you have.

 

when i have this issue i go by process of elimination. you do not even have to drive the truck.
pump up brakes 10-15 times till wheels lock. loosen bleeders. if pressure is released and wheels now spin, the problem not in calipers, it is in the lines or master.
pump brakes again. loosen lines at master cylinder. if pressure does not release and wheels do not spin, the problem is in the soft lines going to the calipers.
if pressure releases and wheels spin, the problem is in the master.
pump brakes again and unbolt master from booster. if pressure does not release and wheels do not spin, the problem is the master cylinder.
if the pressure releases and wheels spin, the problem is in the booster.

 

I have done some of these suggestions. I'm going to do it just like your process of elimination and see what happens. The only thing not normal now is I have adjusted the booster rod from original position. I will ignore that for now and do your process of elimination. Sandy

 

TJC I just put my tires back on and did your step one. After pumping brakes, wheels were very tight and only moved by force. I loosened both front bleeders and fluid ran out and the wheels will now turn about 1/8 of at turn by hand but they do move with less resistance. Rotors didn't spin without a tool before I put tires back on. I am unsure if this means this means my issue is the lines or master like you said, or are they good or not like they should be?

Last night I ordered new master lines and a new caliper crossover line that goes to each wheel. They won't be in till next week. At this point should I wait for them or proceed to step 2? Your step 2 is to confirm if the rubber hoses are good. I replaced them last week and SHOULD be good. What is logical to do now?
Thanks Sandy

 

This sounds like a nightmare Sandy. I hope you get if fixed soon. I'm wondering if I should attempt my front brakes now. Good luck.

 

Thanks Glenn. It has been interesting and I enjoy learning so it's good. Hoping TJC's plan works. Sandy