i have a '93 corsica as well; i have had to replace the front brake line components and one rear. in the front, the brake line part that goes from the calipers to the steel brake-line connection often rott out and leak as mine did.
they should be replaced even if that isn't the leak on a car this old. as the previous responder said...pump the brakes several times with the master cylinder full and look where the fluid is coming from.
the one good thing about brakes is they are very easy to diagnose the problem especially on a car this old. if it's a metal part of the brake-line that is leaking i recommend having a mechanic replace it.
mine has 170,000 on it and runs fantastic so it's worth it.
Heater core is leaking. Air Conditioner drain hose is plugged.
chances are its a leaking brake booster or rear seal on master cyl.
Master cylinder may be leaking, brake pedal may slowly fall to the floor when you are stopped with your foot on the brake.
most likely cause is your heater core leaking
Probable causes: Low or no fluid in reservoir; Worn brake pads/shoes; Air in brake lines; Leaking brake line.
Leak in heater core
more than likely the windshield is leaking and the water is running behind the dash onto the floor.
Master cylinder failure.
Probably leaking back at the master cylender.
Vacuum brake booster is defective or the hose going to the booster is leaking.
it could be a lot of different factors such as master cylinder is leaking past seels, crack in a brake line, leaking wheels cyclinders or calipers, air in the brake system that will cause brake pedal to go to floor if it is hard and wont move could be a failed brake booster
Check for a sickly sweet smell. The heater core is probably leaking coolant into the floor. The core is not repairable but can be replaced.