How do I check my mechanical temperature gauge?

Mechanical temperature gauges may be checked by placing the bulb end of the capillary tube in a container of engine coolant or oil of known temperature. Use an accurate thermometer in the liquid to help ensure accuracy and continuously stir the liquid. Wait at least 10 minutes for the bulb temperature to equalize with that of the thermometer. If the indications on the gauge do not correspond to the indications of the thermometer the gauge is defective. Caution - this test should only be done by personnel with proper equipment and training to avoid possible injury or damage.