Which of the following is NOT a cause of engine overheating?

A stuck open thermostat actually allows coolant to flow continuously, which can help maintain an appropriate operating temperature and prevent overheating. If the thermostat is stuck in the open position, the engine will not reach its optimal operating temperature efficiently, but it is unlikely to cause the engine to overheat.

In contrast, a defective fan clutch, clogged cooling system, and broken fan shroud can all significantly impair the engine's cooling efficiency. A defective fan clutch can prevent the engine cooling fan from spinning at the necessary speed, particularly under high load or high temperature conditions. A clogged cooling system restricts the flow of coolant, which can lead to localized overheating. A broken fan shroud can disrupt the airflow over the radiator, further decreasing the cooling capacity. All these factors contribute to overheating issues, while a stuck open thermostat does not.