Pressure wash the engine and everywhere that looks like you might be leaking. Let the engine dry thoroughly then put the front up on ramps or jack stands and start the engine to get it hot. Watch for the leak. If it's comming from under the water pump housing, you probably have a leak around the water pump input shaft and will need to replace the pump. If it's around a hose or at a gasket contact point replace the gasket or hose.
your heater core is leaking
1991 Corsica its under the trottle body
Green coolant (prestone, etc)
Place something to catch the engine coolant beneath your 1990 Chevy Corsica radiator. Remove the radiator drain plug with a 9/16 ratchet. The engine coolant will drain out.
It could be the coolant overflow tank that is leaking.
Leak in heater core
Mine does not. Perhaps you a low on coolant.
The heater core has failed and is leaking engine coolant.
If the coolant fan does not operate on a Chevy Corsica, it is likely that a fuse is out. There could also be a mechanical defect in the fan or wiring.
Intake manifold at top of engine?
your heater core is bad
If there is coolant coming from it and it isn't a hose.