strange brake condition

[GM_Guy]

I am having a brake issue in My 82 GMC van. when I press on the brake, normally it will be firm, other times it will start firm, then go to floor slowly, setting the brake light. when this occurs, I press down hard, and light goes out. do I have something to worry about????

[Cableguy]

I'm not liking the sound of that Jeff. Have you checked top to bottom for leaks in hydralics? Resevior to bleeder screws.

[84fiero123]

Air in the lines,

Leak in the lines,

Leaking master cylinder,

All dangerous and should be corrected immediately.

Look for wet spots near any brake part, lines.

Then fix.

[TrailLeadr]

To me it sounds like bad master cylinder.