Thermostat Test

WARNING: This page is about a different car, the 2009 Acura MDX, 2008 Acura MDX, and 2007 Acura MDX. However, it is still accessible from the selected car via links, so may be relevant.

Replace the thermostat if it is stuck open 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: Suspending Thermostat In Container Of Water
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Heat the water and check the temperature with a thermometer. Note the temperature when the thermostat first opens, then check the temperature when the thermostat 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)