A display on your liquid-cooled vehicle indicates that the temperature of your coolant is excessively high. What might be the cause of this?

The combination of choices 1, 2, and 3 is correct because each of these factors can independently contribute to an overheating coolant problem in a liquid-cooled vehicle.

1. If the radiator is contaminated with dirt, it can obstruct airflow and reduce the cooling efficiency, leading to higher temperatures.
2. If the radiator fan has stopped working, it can prevent air from flowing through the radiator, which is crucial for cooling the coolant.
3. A perforation in the radiator system can lead to coolant leaks, reducing the amount of coolant available for circulation and thus causing overheating.

Understanding these issues is important because maintaining proper vehicle temperatures is not just a matter of performance but also crucial for safety on the road, as overheating can lead to engine failure. According to German traffic regulations, drivers are responsible for ensuring their vehicles are in safe working order, including monitoring coolant levels and temperature to prevent breakdowns that could pose hazards to themselves and others on the road.