Most vehicle thermostats are located at the connection point where the top radiator hose joins the engine block; the units can also be located in the bottom radiator hose. Vehicle thermostats are generally about 2 inches in diameter.
Rapid overheating of a vehicle or gurgling sounds coming from the radiator can indicate a bad thermostat. Many partially stuck thermostats can cause a vehicle to run hot but not overheat, whereas a unit that is stuck open can keep the car's heater from working properly in the winter. Thermostat replacement is a simple task; simply disconnect the radiator hose from the thermostat, unbolt the unit and remove it. Replace it with a new thermostat and gasket.