How Does a Car Thermostat Work

How does a car thermostat work? The thermostat is an important part of your car's cooling system, designed to regulate the operating temperature of your car's engine.

How Does A Car Thermostat Work So Well?
A gallon of gasoline, when burned, generates enough heat to boil 120 gallons of water. So how is it that the two gallons of coolant are enough to keep your engine running at the right temperature? All of the parts of your car's cooling system work in concert to carry away waste heat, but the thermostat is in charge of regulating all of the action. Here's how it's done:

  • Anatomy of a cooling system. The engine block of your car's motor is lined with channels (called cooling jackets) that allow coolant to flow through the metal, keeping it cool. The cooling jackets are connected to a radiator, which holds the coolant and passes air over the liquid to keep it cool. A water pump circulates the coolant, replacing hot engine liquid with cooler radiator supplied liquid. The thermostat regulates how much coolant flows into the engine based on the temperature of the engine itself.
  • It's a temperature thing. The thermostat uses a valve to control the flow of coolant into the engine. When you start the engine, the valve is close, restricting the flow of coolant into the engine. The lack of coolant helps the engine warm up faster, resulting in reduced engine wear and harmful emissions. Once the engine reaches its operating temperature, the thermostat opens its valve releasing coolant into the engine.
  • Under pressure. The magic in your car's thermostat is a little ball of wax. The thermostat's valve is connected to a cylinder and spring mounted piston. The cylinder is filled with wax that melts at a specific temperature. When the engine warms, the wax melts and expands as it changes from solid to a liquid. The pressure of the expanding wax pushes the piston out of the cylinder and a rod connecting the piston and valve forces the valve open. With the valve open, coolant can flow freely through the cooling system. When the car is shut off, the wax cools and contracts and the spring pushes the piston and valve back into their closed positions.
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