Thermostat Test

2006 Chevrolet Cobalt SS, 4D Sedan, StandardSECTION 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:

  1. 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
    G06429085Courtesy of AMERICAN HONDA MOTOR CO., INC.
  2. 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.
  3. 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) 

RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.