Blows cold air from heater. Replaced Thermostat. Still blows cold air.

Will try to help. is your radiator full of fluid? sometimes there will be an air lock, or [air in hoses] with the engine running at first started!!! take the radiator cap off, fill with 50/50 antifreeze. or if you are in alaska, seek advice from local parts store on level you need for coverage.you may have a bad bad heater core, but not likely because you would say you have fluid leaking onto passenger side floorboard.you may have purchased the car used?somewhere there is a blockage in your system.either a bad radiator,heater core,i will try to help because i've had same problem,in the FRONT OF RADIATOR]place a small peice of cardboard in the front of radiator!!ONLY COVER HALF OF THE RADIATOR] slide it down in front of the radiator on the side of the part where the radiator fan is not at. then you will have heat. if yout engine temperature rises to unsafe level, cut cardboard in half and replace!!!make sure;to put in front of the radiator only!!!this will apply heat to car while in motion!