What do hot spots in the combustion section of a turbojet engine indicate?

Hot spots in the combustion section of a turbojet engine typically indicate malfunctioning fuel nozzles. When fuel nozzles are not delivering fuel uniformly or are delivered at the wrong rate, certain areas within the combustion chamber may experience higher temperatures due to uneven combustion. This uneven combustion can create localized overheating, referred to as hot spots, which can lead to further damage in the engine components if not addressed promptly.

The other options relate to different systems or malfunctions. Excessive combustion pressure may lead to performance issues but is not directly indicated by hot spots alone. Clogged air filters could affect airflow, leading to broader engine performance problems but wouldn't specifically create localized heating in the combustion section. Coolant failures are more relevant to engine cooling systems and do not directly relate to how fuel is combusted within the combustion chamber. Therefore, the presence of hot spots is most accurately associated with issues stemming from malfunctioning fuel nozzles.