Which of the following is a sign that the radiator may need cleaning?

The indication that the radiator may need cleaning is primarily associated with the engine overheating during operation. A clean radiator is essential for efficient cooling, as it allows for proper airflow and effective heat exchange. When debris, dirt, or corrosion accumulate in the radiator, it can restrict airflow and reduce its ability to dissipate heat. This leads to an increase in engine temperature, often manifesting as overheating.

Overheating can result in various issues, including potential damage to the engine components if not addressed promptly. Therefore, recognizing that the engine is overheating is a critical sign that the radiator requires inspection and possibly cleaning to restore its performance and ensure the engine operates within the optimal temperature range.