2002 Chevy Cavalier removal of thermostat

Should be located in a removable housing at the engine end of the upper radiator hose

Drain about 1 gallon of coolant from the radiator

Remove this housing

Make note how thermostat is installed

Clean both surfaces

Replace thermostat and gasket

Re-install housing

Re-fill coolant slowly to prevent an airlock

Start engine and look for leaks

Run engine to normal operating temperature with heater on

Re-check coolant level