Where is the thermostat housing on a 2002 Chevy Malibu?

The thermostat housing on a 2002 Chevy Malibu is located on the top of the engine, at the front of the engine block, near where the upper radiator hose connects. It's generally a somewhat prominent casting with the thermostat and housing itself being relatively easy to see once you have some visual access to the engine. You'll likely need to lift the hood to get a good view.