The thermostat is a valve that controls coolant flow. It opens or closes depending upon the temperature of the engine. A thermostat replacement is needed when the thermostat does not open and close properly. If the thermostat becomes stuck in the open position, the engine will take longer to heat up which can cause poor heater performance, higher exhaust emissions, and the check engine light to come on. If it remains in the closed position it can cause the engine to overheat.
To perform a thermostat replacement, the cooling system is drained, the radiator hose is removed from the thermostat housing, and the housing is disassembled and removed from the engine. The thermostat along with its housing gasket are replaced, the housing and hose are reassembled, and the cooling tank is filled with new coolant.
Most manufacturers have specifications on how to perform a thermostat replacement. This factory recommendation must be adhered by to maintain the validity of your new car warranty and extended auto warranty, if applied. If mechanical breakdown occurs due to the improper installation of the thermostat, then the warranty would not cover the car repair.