2004 silverado overheating
 

Hello, just bought this 2004 Silverado 4WD , 5.3 engine.
Truck had been sitting for about 2 years.
Started overheating so i shut it off and let it cool down.
Added coolant. Ran fine for quite awhile, then started overheating again. Coolant leaking from front area of engine near water pump.
Could it be a bad thermostat or is it most likely the water pump.
Would appreciate some guidance before I start throwing $$$ at things that aren't needed.
Also, this morning, went out to truck and added coolant before it was started. coolant immediately started leaking on ground from same location.
Thanks in advance,
Pete

the 5.3 is known for the O-Ring style gaskets on the water pump failing (I have done Hundreds). if it is flowing out, your water pump my be toast. also. look behind the ac condensing coil at your rad. they will plug up with cotton wood. the ac coil will look clean but the rad.(behind the ac coil) seams to hold debris.