'96 Ranger 4.0, Auto Trans–– Brake Pedal was sticking when pressed but truck still stopped okay. I replaced the master cylinder with a new one. Pedal improved. Brakes feel fine now, but pedal only returns to just below the brake-light switch being at the on position-- right at the edge of brakes starting to apply. Feels like the booster is working properly. A slight lift and the pedal returns to full-up position (and stays there). Any ideas? I can't find anything obvious that the pedal is hanging on. Should I replace the booster?

 

Loosen and pull the master forward again, off the booster, push brake pedal down and pull it back up with your hand to see if you feel it sticking anywhere, there are bushings on the rod the pedal pivots on, they can wear out

There is an adjustment on the boosters push rod end where master bolts on, just a nut that can be turned in to make arm shorter or out to make it longer, you may have to adjust this for the new master
When brake pedal is up all the way the end of the booster push rod should just be touching the master's piston, you don't want brakes applied when master is tighten down, lol, but also don't want a gap between booster's rod and master piston