A pyrometer is a useful instrument for checking _______ in a diesel engine.

• A. Oil pressure
• B. Coolant temperature
• C. Exhaust temperature
• D. Cylinder head temperature

Answer: (C)

A pyrometer measures temperature by detecting infrared radiation from a hot object. In a diesel engine, the exhaust stream is among the hottest places, so a pyrometer is used to monitor exhaust temperature. This reading helps protect exhaust components and turbochargers and supports diagnosing combustion quality and fueling issues. Oil pressure and coolant temperature are measured with pressure or coolant sensors, not with a pyrometer, and cylinder head temperature is typically read with a thermocouple or embedded sensor. So the instrument is best suited for checking exhaust temperature.