I have a '79 F-250, 4wd, 400M, 4 speed. I have no pedal return after depressing the brake. The pedal stays down and the brakes stay engaged until I lift it with my foot. I could find no place for a return spring on the pedal. I then replaced the booster/master cylinder. Still no luck. I have 20-21 in. of vacuum, so that's not a problem.
I'm not sure where to go from here. I have never heard of a pedal being returned by the booster before, so this is a new experience for me.

 

I am guessing that you bleed out the master cylinder an the brakes after you replaced it ???if the pedal moves freely with the master cyl removed, then I would have to say probaly your booster has failed, ,, It's spring / hyd pressure that returns your brake pedal ,Theres a spring inside the master cyl that returns the plunger . ,, If you remove the Master Cyl . an push in on the back of it with a blunt screw driver you will feel some resistance, As you release the pressure the plunger returns , thats what kicks your pedal back up .. do you hear any kind of noise thats sorta a wooshing sound in the brake pedal area with the engine running, or brake applied ?, thats normally the sound of a faulty booster, normally to check a booster after you shut the vechile off an you pump the brakes they should get harder an harder to push till the pedal has very little travel , if they sink , you got a bad booster or a bad check valve , that thing that the large hose hooks to on the booster---- I have seen the pedal linkage get dry an bind up an stick down as you say , to check that loosen the master cyl , pull the rod off the brake pedal , the pedal should move very free with no effert if not the linkage is froze an those are fun to play with . Also there is a rod in the brake chamber that is adjustable{ DO THIS ONLY AS A LAST RECOURSE AN ONLY TURN IT LIKE 4 TURNS MAX !!!!! } we'll save this for a later post as it will keep your brakes applied all the time an the only way to release them is open a bleeder an the readj . the rod after you pull the master cyl back off-- not something you want to do on the side of the road .