1994 Chevy Silverado Coolant leaks

My '94 Chevy 1500 156000 miles. Is leaking coolant from between the fan and engine. At first I changed lower hose and replaced Thermostat, started it, let it idle for 20 min. with the radiator cap off, noticed the temp gauge on dash was not showing any temperature, drove it and the dash temp. gauge still was not moving. I drove about 20 miles and when I stopped coolant was leaking, again. It doesn't seem to be a hose, what is this and is it costly to repair??
Thx