Where does the car leak if heater core is out?

If your heater core is leaking it will leak into your passenger compartment or the plastic container that normally houses them. Your windshield will get sticky steam on it if you turn on your defroster and the interior will smell like antifreeze ( sweet smelling ). Your heater may not be getting water because the heater hose that supplies it with coolant from your engine is leaking. This hose will go from your motor to your firewall as will the return hose. Another reason your heater may not blow hot air is a thermostat that is stuck in the open position, never allowing your motor ( or the coolant ) to properly warm up. In this case you will find no leaks.