Where is the thermostat located on a 2004 chevrolet silverado 1500?

i am an owner of a 2004 chevrolet silverado, well i have drained it once but come to find out the 2004 chevy doesnt have a drain plug you have to drain it through the radiator hose! well i did so and ever since i drained it(which was like a week ago) i smell the antifreeze and the truck still gets overheated,and its drainedd of the water that WAS in there! any suggestions?