Quick history to get to the present on my 79 F150......

A few months ago I blew a front pass side brake hose, replaced hose, bled, brakes work good. Started noticing a small leak in the brake line on the drivers side, pedal got soft and low before I had a chance to "get around to it", tightened banjo bolt on caliper, bled, brakes work good again. Four days ago (tues morning) once I got to work notice I had a brake hanging up, by touching the drums and rotors I assumed it was the pass side front since that was the one that was hot (yes quick sizzle of my finger) when i got back the next day and went home it was not hanging up any more so i figured this weekend I would replace the sliders since I've questioned them since the last time I did brakes. Well Thursday on the way to work they stuck on big time, this time by the time I got off the road and into a parking lot both front sides were hot enough that they were smoking.

I tryed wiggling them around w/ a small prybar since I still suspected the sliders (although that hope was fading since it was now both sides) but this helped nothing. Had the truck towed home while I was out Thurs night and haven't had a chance to look at it tonight since getting back but I suspect that they have released again.

All in all I'm stumped as to what this would be . Any ideas on the problem and solution would be greatly appreciated.

 

make sure you are using the correct type of brake fluid and that you dn't have any water in it. Also check the return port on the master cylinder.

 

Yep using correct fluid and from all the bleeding the system has gotten a good flushing. Nice clean and clear fluid at all four corners. How would I check the return port on the master cylinder? FWIW I replaced the master at the same time I replaced the blown hose.

 

TRUCKDRIVINFOOL, what i'd check is your brake calipor, i bet the piston is sticking, your brake fluid should be Dot 3, same thing happened to me , L/F brake stuck so bad my rotor turned " BULE " , i was on vac., i replaced my calipor one side brake pads and on we go.

 

Ok I finally got a chance to look at it and heres what i know

The calipers aren't the problem, I got them to stick on again and pulled the calipers off and tried to push them back. The only way they would go back was to open the bleeder, then they went back easily and when i put them back together the slides work smoothly. That leaves me to think that either the proportioning is sticking, the master cylinder is sticking, or there is a chunk of of crud in the line somewhere between the junction block that splits the lines at the front axle (since both side are sticking) and the master cylinder.

1. Would the prop valve really stick and not let fluid flow back? Have found some posts here about trouble w/ the light staying on and poor brake performance from this but not my situation.

2. Could my new master cylinder have something stuck in it?

3. After all the bleeding could there really be a chunk of crud thats allowing the fluid to only go one way?

 

I dont want to sound off in the wronge way , but if your piston inside your calipor has a bad spot (rust) ? or pit it well slide in and out to a point , then it well bind up, if you have 40,000 mile or so and never O/H them you might think about it.good luck

 

Would anyone know for sure if there would be a difference between a master cylinder for a 76' and a 78'?

Last night while tinkering I got the brake to release by loosening the line to the fronts at the master. It was holding pressure at that junction that made a good little squirt, so i figured if something before the master was not letting the fluid go back it shouldn't hold pressure there.
So I got the master warranted and as I put the new one on I noticed hat it wouldn't slide over the studs and sit completely flat against the booster w/o tightening the nuts. I thought that was kind of odd but didn't think too much of it at the time.
After bleeding and test driving the problem wasn't quite as bad but they still hang up a bit and that got me to thinking and remebering that the cab on my 76' is from a 78'. As I looked through a part site they listed two different part#s for masters.
So back to the question above would there be eough difference between the two that the little bit of sinching down would be putting pressure against the piston in the master and holding the brakes on?

*Edited for being an idiot* - just notice orgional post said 79', but it is a 76' chassis w/ a 78' cab.

 

I had a similar problem on my 83 Ranger plow truck. It would lock up after pushing snow for an hour or so. Fortunately, there was lots of snow around to cool it off, but it would sizzle! Took it apart several times, bled the system, etc, etc. I finally replaced both front calipers, and the problem went away. I think the pistons were locking up when they got warm. After sitting over night, everything worked fine, until I heated up the brakes the next time. I should have taken the old one's apart to see what they looked like, but I didn't, so I'm just guessing.

 

Thank you hreed , i wounder if anyone read what you said. ? lol,,,,,,,,,,,

 

Could be the brake pedal rod going into the master cylinder. It needs to back-off and let the master cylinder completely retract.

 

Fordberg hit it on the head. I didn't think that there was any adjustment to the rod coming out of the booster but when it was said I figured it wouldn't cost me anything to pull it back off and look.
I adjusted the rod in about one turn this morning and have the problem solved.

TNT- I did read what was said and can only come to the conclusion that I didn't make it clear enough that the brakes would release when the built up hydraulic pressure was released by opening a bleeder or line thus ruling out a stuck caliper. I guess I'll have to try and make myself clearer in the future.

Thanks to all that replied