Thermostat Test

WARNING: This page is about a different car, the 2008 Acura TL and 2007 Acura TL. However, it is still accessible from the selected car via links, so may be relevant.

Replace the thermostat if it is in the stuck 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: Checking Thermostat Operation
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Heat the water and check the temperature with a thermometer. Check the temperature at which the thermostat first opens, and at which it is fully open.
Measure the lift height of the thermostat when it is fully open.
Standard Thermostat

Lift Height: Above 10.0 mm (0.39 in.)

Starts Opening: 169-176°F (76-80°C)

Fully Open: 194°F (90°C)