What should be checked if temperatures are abnormally low?

If temperatures are abnormally low, checking the thermostat closing is crucial because the thermostat plays a vital role in regulating the engine's operating temperature. When the engine is started, the thermostat is closed, allowing the coolant to heat up quickly. Once the engine reaches its optimal temperature, the thermostat opens to allow coolant to flow through the radiator, preventing overheating.

If the thermostat is stuck in the closed position or does not open as it should, it can cause the engine to run cooler than intended, leading to inefficient fuel combustion and increased emissions. Conversely, if the thermostat remains open continuously, it won't allow the engine to reach its ideal operating temperature. Thus, ensuring the thermostat is functioning correctly is essential for maintaining proper engine operation.

While other components like coolant levels, water pump speed, and radiator fan operation are crucial to the overall cooling system, they do not directly influence the engine's temperature regulation as effectively as the thermostat's operation does.