The thermostatic valve in the illustration is used for controlling the coolant temperature in a main propulsion diesel engine. Which of the following can be used to verify proper valve operation with the valve disassembled? Illustration MO-0079

Correct Answer: Option D — Place the thermostatic element in a container of water at various operating temperatures and note the movement of the valve stem.

Testing wax-pellet thermostatic elements requires submerging the thermal actuator in a controlled water bath while gradually increasing temperature to verify correct valve stem displacement and calibration against manufacturer specifications.