Lesson 5/Learning Event 1
FIGURE 73. COOLANT FLOW - THERMOSTAT CLOSED.
When the engine is cold, the thermostat shuts off the flow of coolant from the engine to the radiator. This
causes the engine to heat up quickly. However, if the coolant is allowed to stand still in the engine at this time,
hot spots may occur and the engine will not warm up evenly. Engines have a bypass passage that allows
coolant to be pumped through the engine without going through the radiator to prevent this.