why does my brake pedal go to the floor when the car is running? on 2000 Ford Taurus

Driving my car one day and everything is fine, I park and let it sit for 2 days before driving again. But this time when I start the engine and try to shift to drive my break pedal goes all the way to the floor I can't figure out what is wrong. I checked for leaks, found none I added break fluid and still they don't work, what else could it be?

by in Cincinnati, OH on June 23, 2014
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1 answer 2 comments
ANSWER by , June 23, 2014
Internal leaking of the master cylinder. How empty was the reservoir , that you needed to add brake fluid?
COMMENT by , June 24, 2014
It was low, does this mean I have to replace the master cylinder ?
COMMENT by , June 24, 2014
NO , at this point , it should be properly diagnosed by a qualified person(s), you may have problems elsewhere in the system.