There are two basic types of thermostats currently available: You have the balanced sleeve thermostat, and the reverse poppet thermostat. Both types function in the same manner, but have distinct differences. The reverse poppet thermostat opens against the flow of coolant from the water pump. The coolant, being under water pump pressure, is used to help the reverse poppet thermostat stay closed when it is cool so as to prevent leakage.
The balanced sleeve thermostat allows pressurized coolant to circulate around all of it's moving parts, and equalizes the system pressures above and below the thermostat’s moving valve. Therefore the thermostat is pressure balanced and will respond to system temperatures only. It provides a fast temperature response time and increased coolant flow to the radiator. For a performance engine application it is recommended to use the balanced sleeve design for it's added flow capabilities. See photo below:
John
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John
"There are no stupid questions, but there are a LOT of inquisitive idiots!"
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