Join Date: Jan 2005
Location: San Juan Capistrano
We could diagnose the exact failure mode of your MC all day long, but the bottom line is that you need to replace it pronto. Having the pedal go to the floor is NOT good. The fact that pumping fixed it the first time doesn't guarantee that it will work the next time.
When you pull off your old MC, you can try using a turkey baster, or other source of suction to see if there is old brake fluid down in the booster. Yea, some of it would have gotten drawn into the engine, but some will remain puddled down there. Use the baster, then stuff in rags / ppr towels to get as much out as possible.
As ghnl says, the booster will eventually die due to exposure to brake fluid (and no, that doesn't make sense to me either). But, it will last for awhile longer - perhaps a few years. And, when the booster does fail, the consequences aren't that dire - it just takes more muscle to stop the car, but unless your petite, 90 pound wife routinely drives it, that's not a big deal.
San Juan Capistrano, CA
'63 Guilia spider
'65 Guilia Sprint GT