maybe brakes? on 1993 Buick Century

my brake pedle some times just goes all the way to the floor bord but if you pump it they get right i already blead them and added brake fluid (just to monitor for leaks none yet)so what could be my problem?

Asked by for the 1993 Buick Century
It sounds like the brake master cylinder is failing. If there are no leaks a repair shop may disconnect the brake lines from the master cylinder and temporarily put in blanking plugs, bleed the master cylinder and then see if the cylinder can generate and maintain pedal pressure in an effort to prove it is the brake master cylinder that is defective. Frequently when the brake master cylinder is failing or there is "mysterious" brake fluid loss, a stain of brake fluid may be seen where the brake master cylinder is mounted to the brake servo unit/ brake booster.