Which statement about normal mechanical fan clutch operation is false?

The correct answer involves understanding the operation of a normal mechanical fan clutch. A fan clutch is designed to engage and disengage the engine cooling fan based on the temperature of the engine coolant rather than the speed of the engine itself. This adjustment is key to maintaining optimal engine temperatures and improving fuel efficiency.

When the engine is cold, the fan may not spin as fast or may stay disengaged, allowing the engine to reach its operating temperature quickly. As the temperature rises, the fan clutch engages, allowing the fan to spin faster and provide increased airflow to cool the engine.

Statement regarding variation of fan speed based on engine speed is incorrect because while engine speed can influence the overall cooling system performance, the fan clutch primarily operates based on engine temperature rather than directly reacting to engine speed. This distinction helps the cooling system use energy efficiently and respond appropriately to different cooling needs.

Options about viscous drag, the fan's response timing post-engine shutdown, and temperature variation properly reflect how a mechanical fan clutch is designed to operate, reinforcing the importance of temperature as the main factor in fan engagement rather than the engine speed.