Engine Cooling System: Thermostat
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A diaphragm-type thermostat controls the operating temperature of the engine by controlling the amount of coolant flow to the radiator. The thermostat is located inside of the thermostat housing. On all engines the thermostat begins to open at 88°C (190°F) to allow flow to the radiator. The thermostat is fully open by 100°C (212°F). This provides quick engine warm up and overall temperature control. The same thermostat is used for winter and summer seasons. An engine should not be operated without a thermostat, except for servicing or testing. Operating without a thermostat causes other problems such as longer engine warm-up time, unreliable warm-up performance, increased exhaust emissions and crankcase condensation. This condensation can result in sludge formation. The wax motor is located in a sealed container at the spring end of the thermostat. When heated, the internal wax expands, overcoming closing spring tension and water pump pressure to force the valve to open.