The engine coolant thermostat is mounted in the cooling system and restricts the flow of coolant until the
engine reaches operating temperature. Once the engine coolant temperature has reached a certain point (typically
180-195 ºF) the thermostat opens and allows coolant to flow through the radiator. We stock a complete line of
thermostats covering most Fahrenheit ratings. Name brands include Beck/Arnley, Stant, Mr. Gasket and MotoRad.
Each includes a limited warranty against defects. We also carry some models from Wahler, a manufacturer that
specializes in parts for European cars.
The thermostat hasn't really changed much in 100 years. It's still the same device that prevents the flow of
coolant into the radiator until the engine's warmed up, then allows coolant to flow through the entire
engine and cooling system when the engine reaches a specific temperature.
A thermostat’s design is simple: it contains a wax pellet inside a sealed chamber, and when the wax pellet
heats up enough to melt, a valve opens and allows the flow of coolant. Many makes and models provide coolant
flow through the heater core, regardless of whether the thermostat is open or closed.
A failed thermostat that's stuck closed may result in an overheated engine, while a thermostat that's stuck
open might mean an engine that never warms up to operating temperature. If you're curious about your
thermostat, it's easy to test - just remove it, put it in a pan of water on the stove, and turn on the heat
to see if the thermostat pops open.