Thermostat Test

WARNING: This page is about a different car, the 2011 Honda Insight and 2010 Honda Insight. However, it is still accessible from the selected car via links, so may be relevant.

Replace the thermostat if it is stuck in the open position at room temperature.

To test a closed thermostat:

Suspend the thermostat (A) in a container of water. Do not let the thermometer (B) touch the bottom of the hot container.

Fig 1: Measuring Lift Height Of Thermostat
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Heat the water, and check the temperature with a thermometer. Check the temperature where the thermostat starts to open, then check the temperature again when the thermostat is fully open.
Measure the lift height of the thermostat when it is fully open. If the thermostat is not within the specification, replace it.
Standard Thermostat

Lift Height: Above 8.0 mm (0.31 in)

Starts Opening: 169-176 °F (76-80 °C)

Fully Open: 194 °F (90 °C)