Lesson 5/Learning Event 2
FIGURE 74. COOLANT FLOW - THERMOSTAT OPEN.
When the proper engine operating temperature is reached, the thermostat valve opens and allows coolant to
flow through the radiator. If the weather is cold or if the engine is operating at less than full power, the
thermostat does not open up all the way. It will allow just enough coolant to flow through the radiator to keep
the engine at the proper temperature. When the engine load changes, the thermostat valve opening changes,
providing just the amount of cooling that is needed.