Double pump brakes

If the same fault shows up again, buy a master cylinder. They do bypass internally at random. Works fine for days then suddenly the pedal goes to the floor. A quick "pump again" response makes brakes. I've aways called this event "warning shots" fired by a failing master cylinder. I don't believe this is an engineer's brainchild safety feature either. I believe its a unexpected blessing for all of us.
The ones that sticks in my memory the most was a big ol' green 73 Impala we owned. Wife complained that it had happened a couple of times while she was driving it to and from, so we traded rides. I drove the thing to and from almost a week before it happened to me.