How to Determine if a Thermostat is Good or Bad?
2 Answers
Methods to determine the condition of a thermostat are as follows: 1. When the engine starts cold operation, if there is still coolant flowing out from the upper water chamber inlet pipe of the radiator, it indicates that the main valve of the thermostat cannot close; 2. When the engine coolant temperature exceeds 70°C, if there is no coolant flowing out from the upper water chamber inlet pipe of the radiator, it indicates that the main valve of the thermostat cannot open normally, and repairs are needed at this time. The inspection of the thermostat can be performed on the vehicle, and the methods are as follows: 1. First, observe whether the coolant is sufficient. 2. Check the water flow rate after the engine starts. 3. After the water temperature rises, check the changes in water flow rate and temperature.
As a seasoned driver with over 30 years of experience, I primarily rely on changes in the temperature gauge to assess the thermostat's condition. After starting the engine, the normal coolant temperature should steadily rise to the optimal range (around 90°C) within 5 to 10 minutes. If the gauge suddenly spikes then drops, or remains stuck at low temperatures, it usually indicates a stuck thermostat. Another method is touching the hood - if it feels scalding hot while the dashboard shows low readings, that's a red flag. I've also encountered situations where the cooling fan runs nonstop, signaling cooling system malfunctions. Untreated engine overheating can cause cylinder scoring (expensive repairs) and sometimes increased fuel consumption. I recommend checking the temperature gauge during car washes and visiting your trusted mechanic immediately if abnormalities occur - early intervention prevents major damage.
