My son's '76 LT say while he was away at college. Now I find that the rear wheels didn't want to move even though the car was in neutral with the parking brake disengaged. I pulled the drums and pulled on the cables- now it rolls but:

•The parking brake engages, but will not "SPRING" back up- I have to lift it bu hand
•The regular brake pedal goes directly to the floor when the engine is started and does not pump up- in fact there is a hiss (short one)when the pedal is pressed.
•I vacuum bled the brakes, but it didn't help- still NO brakes- still the pedal goes to the floor
•The dash BRAKE light remains on all the time.

Any help to get me started may help cure the remaining symptoms.

Could it be the combination valve needs replacing?

 

First issue: emergency brake cables might be rusted and not releasing.
Second: pedal to the floor is likely a bad master cylinder.
Third: hissing could be either a bad vacuum brake booster, or if the car has cruise control, the brake pedal vacuum release switch up near the brake light switch could be leaking. I had that one before, fooled me into thinking it was a leaky booster. Man was I p.o.'d after replacing the booster only to find it was really the switch.

 

I hope its not the master cylinder, I just replaced it with a new, not rebuilt, one. I don't have cruise control and I also replace the brake booster along with the Master Cylinder. Are there any tests to run?

 

Did you bench bleed the master cylinder? There are two things to cause a dash brake light on. Park brake not returning (very likely with rusty brake cables) or because of the safety switch in the combination valve. Step one is to figure out why the light is on. Some times you can get lucky and lift the park brake with your foot and the light will go out. Also look to see if the light gets brighter when you push the park brake on. If the light gets brighter when you apply the park brake then the light is being turned on by the combination valve.

There are two separate hydraulic systems, when the combination valve detect low pressure on one side it moves to seal that side to prevent the complete system failure. Light on means the valve is not in its center position. They are suppose to return to center once pressure is even but they stick a lot, in fact they would stick 30 years ago when the car where less then 10 years old. I am sure they don't get better with age.

Have you tried taping on the combination valve to see if that will get the switch to re-center? 30 years ago this would fix 9 out of ten valves after a repair.