Fitment: for Volkswagen Jetta 2005-2006 (Suit for 1.9L L4 Diesel Only)
Good Replacement: The engine's thermostat regulates the temperature of the engine by controlling coolant flow. A bad or failing thermostat: high temperature reading and engine overheating, low temperature reading and underheated engine, temperature changing erratically, coolant leaks around thermostat housing or under the vehicle.
How to Fine Thermostat: You can find your car's thermostat by starting at the upper radiator hose and following it to where it enters the top of the engine.