Where does the water go? Kia Sorento 2005

I have a 2005 Kia Sorento EX with a new motor changed out almost 2
years ago now.  Last winter I had an explosion (well not really that bad) but
steam was coming from the area of the firewall around the center of the car
and found to have a heater hose burst so it was replaced.  

Since then, it ran hot, heater blew cold and I have to continuously monitor
the reservoir because it frequently runs out.  During the summer now with
the A/C it'll start to rise in temperature and in the winter with the heater
blowing, it'll run hot when it gets low of water.

Before this began I noticed an odd sound along the firewall area.  There
have been guesses of air in the water lines but it sounds to me like water
being sprayed at a high rate of pressure.

Any ideas where the water could be going?  The sound is maybe coming
from inside the dash like a heater core location but there's never any wet
area to spot so I'm stumped.