Elle, what you said makes perfect sense, except I never let that big master
cylinder get below half full. When bleeding the brakes with a short
stroke, because of the wood, I was especially careful not to introduce
air. At that point, I only thought I had air in my system. I thought I
may have introduced air months ago when I used a one person brake bleed
setup. Never got any air during the bleed. This time there were two of
us doing the bleed. When It went to floor, I thought this could not be
possible. Fluid level was fine and by continuing to pump the brakes,
pedal came up and then we lost it again. Yes, I have also introduced air
into a brake system before on a different car by letting reservior get too
low. Did not want to repeat that mistake when I was trying to get air out
of the brake lines. Thanks for your input.