Welcome to brain Stuff from how stuff Works dot com where smart Happens. Hi. I'm Marshall Brain with today's question. How does the thermostat in a car's cooling system work? Any liquid cooled car engine has a small device called the thermostat that sits between the engine and the radiator. The thermostat and most cars, is about two inches in diameter. Its job is to block the flow of coolant to the radiator until the engine is warmed up. When the
engine is cold, no coolant flows to the radiator. Once the engine reaches its operating temperature, which is usually about two degrees fahrenheit, the thermostat opens by letting the engine warm up as quickly as possible. The thermostat reduces where deposits and emissions. If you ever have the chance to test the thermostat, it's an amazing thing to watch because what they do seems impossible. You can put one in a pot of boiling water on the stove. As it
heats up, its valve opens more than an inch. Apparently I magic. If you'd like to try it yourself, go to a car part store and buy one for a couple of bucks. The secret of the thermostat lies in the small cylinder located on the engine side of the device. This cylinder is filled with a wax that begins to melt at about a hundred eighty degrees fahrenheit. Different thermostats open at different temperatures, but a hundred eighty degrees is a common temperature for a thermostat. To open it, a
rod connected to the valve presses into this wax. When the wax melts, it expands significantly and pushes the rod out of the cylinder, opening the valve. The wax expands so much because it's changing from a solid to a liquid in addition to expanding from the heat. This same technique is used in automatic openers for greenhouse vents and skylights. In these devices, the wax melts at a much lower temperature. Do you have any ideas or suggestions for this podcast?
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