3B, thanks for the input. Yes there is a return spring for the pedal and I have no idea about any previous adjustments since I bought the truck last fall and it was last registered in 2003 or so. The brake lines are newer as are the rubber flex lines so somebody had done this work before I got it, probably when it was last registered. I hadn't done anything with the master cylinder or pedal as far adjustment goes or anything for that matter. I did remove the drums and cleaned with brake cleaner and pressure washer and lubricated the moving parts of each brake assembly as per the manual.
So the other day I did remove the master cylinder and took it apart. It looks essentially new inside. The bore is clean with no rust, pits or rings except for a small amount of crud that had collected near where the piston would be at rest. This was wiped away with my finger for the most part and then some scotch brite type stuff to clean off what was more stubborn. The rubber cups look fine and are pliable so I put it back together. I clamped it in a vise and took a short piece of brake line that looped around from the output of the MC and routed it to empty into the reservoir fill opening and added brake fluid. Pumping the piston in creates a good stream of fluid back into the reservoir but I noticed that when I retract the push rod, there is a slight delay in the piston to catch up, maybe a second or two. I've never done this before and don't know what is normal or correct but guess that the piston with its compressed spring would stay in contact with the push rod always or, maybe the fluid is enough to delay this action. I wish I had done this prior to taking it apart to inspect as that may have told me something, I don't know. I may get to putting it back into the truck today but probably tomorrow.
