Automotive Thermostat

The automotive thermostat is used in the cooling system of an engine cooled by liquid or air. It is used as a valve that directs the engine’s liquid flow to the radiator.

 thermostat 3




Allows fast heating of the engine (the thermostat remains closed while the engine is cool). Keeps the engine operating between the designed temperature limits (after the thermostat is active).

The heart of the thermostat is the temperature sensitive heat motor. A specifically formulated, thermally expansive wax is used and is calibrated to assure prompt and precise operation of the thermostat valve. The wax is contained in a heat conducting copper housing fitted with a stainless steel piston inside a rubber boot. The heat motor itself is placed in a stainless steel assembly.

The thermostat blocks the flow of coolant to the radiator until the engine has warmed up. As the engine and coolant temperature heat up, the wax begins to melt when the temperature reaches the waxes melting range. As the wax melts, it expands. This expansion presses in on the rubber boot which in turn squeezes the piston upward. This upward motion causes the thermostat to open, allowing the coolant to flow through the engine.

In other words, the thermostat provides a securely sealed, heat responsive assembly that keeps engine temperatures within original equipment specifications.


  • Reduce friction and extend the engine’s life.
  • Reach the maximum torque and power.
  • Avoid excessive fuel consumption.
  • Avoid high levels of emission.
  • Minimise fuel consumption and pollutant emission.


The thermostat uses a petroleum-refined thermo-expansive wax that is calibrated according to specification. With the increase of temperature, the wax expands inside the thermo-element,causing the displacement of the stainless steel pin,compressing the spring and opening the valve,which allows the passage of the liquid to the radiator.


Generally near the engine and the upper hose that runs from the radiator.


  • Opened: High fuel consumption and pollutant emission, low power and torque.
  • Closed: Causes the engine to overheat, burning the cylinder’s head gasket, warping the cylinder’s head.

thermostat 2


Important actions when changing the thermostat:

  • Always use a new gasket or seal ring.
  • Bleed the air (remove air bubbles) from the cooling system.
  • Check for leaking after the repair.


Post time: Apr-18-2017
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