On my 1977 308 GTB I'm chasing a strange problem and thought I would turn to the F-Chat Brain Trust for help. Occasionally when I go to brake the pedal will go right to the floor on the first application. On the second it is totally normal. The brakes operate 100% perfectly and the rest of the time the pedal is good and hard. It started last year and continues this year after winter storage. I cannot get it to repeat with any regularity and here is what I have done so far to diagnose: 1. Visually inspected the full braking system. 100% dry and no signs of leaks or problems. The flexible lines are stainless steel and show no visible problems. 2. Flushed the complete system with a full bleed. Found no air pockets to speak of and the fluid (that was only a year old) looked ok. 3. Checked the thickness of the pads and rotors. Thinking that it could be pad kickback I am discounting this theory because the pads and rotors are very thick and you normally need quite a bit of wear for pad kickback to be an issue. Outside of this the booster system seems to be working fine and the main vacuum line was changed 2 years ago. Also I cannot imagine how the booster could affect the hydraulic system it merely assists. My inclination is that the master cylinder has gone bad and needs to be re-built. Of course I'd like a second opinion before taking everything apart. Any opinions or feedback would be most appreciated.