How to Determine if the Thermostat is Faulty?
2 Answers
Methods to determine if the thermostat is faulty: 1. Open the filler cap of the cooling tank and check if there is water flow inside. If not, it indicates that the thermostat is damaged or there is debris stuck between the main valve switches; 2. Remove the thermostat from the vehicle and boil it to observe if it opens as the water temperature rises; 3. Start the engine and after 3 minutes, feel the upper and lower radiator hoses. If the thermostat is functioning properly, the temperatures of the upper and lower hoses should differ, typically with the upper hose being hot and the lower hose being cool. The thermostat is a valve that controls the flow path of the coolant, serving as an automatic temperature-regulating device. It usually contains a temperature-sensing component that opens or closes the flow of air, gas, or liquid through thermal expansion or contraction.
Discovering that the thermostat is faulty, I often rely on observing whether the water temperature gauge shows abnormalities for a preliminary judgment. If after starting the car, the temperature needle remains stationary or fluctuates erratically, it might indicate a malfunction. Another obvious sign is when the heater doesn’t blow hot air, making the car feel chilly during winter drives. You can manually check the temperature of the radiator’s upper and lower hoses: after a cold start and driving for a few minutes, if the lower hose heats up quickly while the upper hose remains cold, it suggests the thermostat is stuck in the open position, preventing the engine from warming up. Conversely, if the engine overheats but the lower hose stays cold, it means the thermostat is stuck in the closed position. A failing thermostat can waste fuel and easily damage the engine block, so don’t ignore these small signs—promptly visit a repair shop for a technician to test it with a multimeter for safety. Regular maintenance, such as checking it when replacing coolant, can also prevent breakdowns on the road.
