On my '58 F600 with the frame mounted vacuum booster the residual check valve is located inside the master cylinder and it comes out when you remove the piston, spring, etc.
To check for brake pushrod length just make sure that when the brake pedal is released there is some freeplay between the end of the rod and the piston in the master cylinder. My F600 has an eccentric bolt that attaches the pushrod to the brake pedal and you loosen the nut and turn the bolt until there is some freeplay between the rod and the piston.

 

thanks awthtx. I wounder if there is also a check valve in the hydrovac??

 

As you said there could be valve. I was just wondering if the brakes were not all adjusted to the correct adjustment, and the right rear brake was adjusted closer to the drum, would it not grab first. And if there was a problem else where in the system would that brake stay maybe locked?????
A few folks had mentioned that there could be a check valve causing the problem. So I did some reading and the service manual said that if there is a frame mounted booster that is where the check valve should be. And when I was looking at the re-build procedures for the master cylinder it showed a check valve behind the piston. Should this be removed?? As I stated earlier the master cylinder was one of the first things I purchased for the truck and maybe there is a check valve in it. If you go to the local auto parts store they would just sale you what’s on the shelf…. I’m just guessing, anybody have any thoughts???????

 

The check valve is inside the master cyl. If you were to take it apart the ck valve would be the last thing to come out, it will be on the end of the spring and looks like disc with small holes in it.

 

I don't know. The brake shop rebuilt my hydrovac so I haven't been inside of it. I'm looking at the Ford Service Manual and they show a breakdown of the Bendix booster and it has a check valve. There is no picture of the Midland booster (my F600 has it) but in the text it says to remove the check valve from the piston so it sure sounds like there are check valves in both styles of boosters.

 

Another thought- are you sure that the brake shoes that are sticking are absolutely clean- no leaking axle seals and no leaking wheel cylinders? Any kind of oil or grease on the shoes could cause them to stick.