1. It is best to check the operation of the thermostat by removing it from the engine. If the thermostat is suspected to be defective, it is recommended to replace it.
2. Remove the thermostat as described in Chapter 3.
3. Inspect the thermostat for excessive corrosion and damage. Replace the thermostat if any are found.
4. To test the thermostat, hang it from a piece of twine in a container of water and heat the water. The thermostat should open when the water boils and close again when the water cools. Replace the thermostat if it does not work as described.