Answering the question as it sits, if something is wet, and you've not just been driving in the rain. Answering the question as it was probably meant, pop the hood, warm up the car, and give it some revs to increase water pressure, then have a look to see if you can trace where the leak originates.
The water pump on a 1991 Subaru Legacy is in the engine compartment. It is found at the base of the engine.
yes it could be faulty without leaking , the impellor on the back could of come away and not be pumping water around the engine , to check this take the radiator cap off and have a look if the water goes up and down when you excellorate the engine , if it does the must be a nother problem
in with the timing belt change them at the same time
your windshield seal has failed
For the heater core. All cars have them.
see this http://users.sisna.com/ignatius/subaru/headgasket.html
Check the 1991 Legacy for a stuck thermostat. Check to make sure that the water pump is working properly.
a 50/50 mix of good quality antifreeze and water
ok 1990-1994 subaru legacy engines are basically the same the water pump on mine 1991 is located on the thermostat housing on the bottom of the engine on the lower tube off the radiator so find your lower radiator hose follow it is should go to the thermostat and the water pump is on that
it is in front of the engine block under the water pump kinda low on the engine
Genuine Subaru Coolant or equivalent (50% water & 50% Ethylene-Glycol basis coolant) as per page 10-13 of the "OWNER'S MANUAL".....
A local library may have the repair manual.