Classic/Antique Car Repair: 38 chev brakes, pressure relief valve, wheel cylinders

Question
After replacing shoes & bleeding the lines, the brake lights will flicker and/or come on while in operation or after shutting off the car. It has a new replacement hydralic brake switch (old one non-functioning); master cylinder cleaned out; wheel cylinders cleaned & inspected. The vehicle had sat for over 15 years and brake fluid seeped out (broken brake shoe return spring on right front). I did notice the brake pedal "bumper" is missing - one is on order. There are no obvious leaks and master fluid level remains constant.

Answer
The only thing that operates the switch is pressure, so if there is no electrical problem, pressure is building up in the lines without stepping on the brake pedal.  

This is usually because the pedal linkage is not adjusted right.  Check to see that there is at least 3/8 of an inch of free play at the pedal before the push rod contacts the piston in the master cylinder.  If you don't provide the free play, a pressure relief valve in the master cylinder is blocked, and pressure will build up.  This can get so bad that the brakes will come on by themselves. It is possible that the missing bumper has somehow affected the linkage to cause this to happen.

It could also be that either the switch is defective, or the electrical wires are touching something to make the lights come on.

Dick