How Can You Test the Thermostat in a Toyota Hilux?

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How Can You Test the Thermostat in a Toyota Hilux?

There are ways to check if a thermostat is working properly, such as boiling it in water o r using an infrared thermometer. What testing method do you recommend?

Lubaba asked on 11 Feb 2025 11:38:48 am

1 Answer

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Car Mechanic Expert - on 11 Feb 2025 11:45:19 am

A faulty thermostat can cause overheating o r poor engine performance, so testing it before replacement is a good idea. Here are two recommended methods to check if your Hilux’s thermostat is working properly:
1. Boiling Water Test Most Reliable

Remove the thermostat from the engine.
Heat water in a pot and use a thermometer to monitor the temperature.
Place the thermostat in the water and check if it opens at the specified temperature usually 80–90°C, depending on the model.
If it doesn’t open o r is slow to respond, it’s faulty and should be replaced.

2. Infrared Thermometer Test Without Removal

Start the engine and let it warm up.
Use an infrared thermometer to check the temperature of the upper radiator hose and thermostat housing.
If the temperature stays low while the engine is hot, the thermostat is likely stuck closed. If the engine takes too long to warm up, it may be stuck open.

The boiling water test is the most accurate, while the infrared method is a quick way to check without removal. If a thermostat is faulty, replacing it with an OEM Toyota part is the best solution.