Alright, guys, that's what happened today. As I had mentioned, I needed to drive the bird to take it back to my painter. So there I go and drive it for about 35 expressway miles and about half way the brake light warning suddenly comes on and then goes off after a minute. So I did not think much about it, but when I reach my exit I realize I have no brakes! By some minor miracle I made it through without hitting anybody and got to the shop. Now this is what happens: the brake fluid is still all there, but if I start the car, the brake pedal goes to the floor, but I have a firm pedal with the engine off. There is no evidence of fluid leaks, so I am thinking of a master cylinder failure so no fluid is pumped through the lines. What do you think?

I'd buy a lottery ticket. Maybe you still have some good luck left.

it sure sounds like a MC failure. You could replace it ("bench" bleed the new one in a vise or in the car (one might be less messy than the other), Your parts house has the kit with the blue plastic fittings/2 short black hoses to do this. First to confirm it is the MC you might cap the MC ports with a pair of brass plugs from your parts house (I forget if 9/16 or 1/2) & might be one of each & if the MC is good, the pedal (eng idling) will be rock hard with virtually no travel, try light pedal & a hard stomp but it sure sounds like the MC. check the pushrod clearance while you are in there.

Good idea, but I already know that the pedal goes to the floor with the engine on, so if the MC were good, fluid would be pumped though the lines and some braking would work. Consider I have a full reservoir and no evidence of leaking fluid anywhere,

I agree & the only other thing that would make it act like that would be if there were a ton of air in there.