Losing brake pressure....Sometimes???

[Felix S <melvnhel@xxxx>]

Hello List,

Another problem which is kind of scary, I seem to be losing brake
pressure when I am at a stop light or pulling out of my driveway. Pressure
I mean the car is stopped then I feel the pedal move, all the way down to
the floor, I pump it and the pressure is back. I would think Master
cylinder etc. but here is the funny part. It happens only sometimes
(haven't seen a pattern yet), the day could be super hot or cold doesn't
matter, there is no leaking brake fluid anywhere, the fluid is always full.
Someone once told me that I had air in my system, maybe but that's kind of
weird. Or an internally bleeding brake master cylinder, so I can't see the
leak? I first noticed this during a parade and we were going stop and go up
a steep incline for a while and then stop and go all the way down, and
that's when I noticed it. Anyone had a similar incident before?
Suggestions?

Thanks in advance

Felix