An important component in the smooth operation of the cooling system, the thermostat limits the flow of coolant through the engine. This reduces the time the engine takes to warm-up and helps maintain the optimum temperature once it’s reached. Thermostats can also often become stuck in one position, resulting in engine overheating or running too cool. This relatively inexpensive item should be on everyone’s list of items to replace every few years, so as to maintain optimum performance. Manufactured by original equipment supplier, Behr.