How to Determine if the Thermostat is Damaged?
2 Answers
Methods to determine if the thermostat is damaged include checking the coolant reservoir. Below are the methods to identify a faulty thermostat: 1. Check the coolant reservoir: Open the filler cap of the coolant reservoir and observe if there is any flow of coolant inside. If there is no flow, it indicates that the thermostat is damaged or there is debris stuck between the main valve and its switch. 2. Boil the thermostat: Remove the thermostat from the vehicle and boil it, then observe if it opens as the water temperature rises. 3. Start the engine: Start the engine and after 3 minutes, feel the upper and lower radiator hoses. If the thermostat is functioning properly, the temperature of the upper and lower hoses will differ, typically with the upper hose being hot and the lower hose being cool.
I've been driving a compact car for several years and encountered thermostat issues twice. Back then, I noticed the temperature gauge rose unusually slow—even after driving for twenty minutes from a cold start, the needle still stayed in the low-temperature zone, and the cabin heater couldn't blow warm air. This was all because the thermostat got stuck and failed to open, preventing the coolant from circulating properly. Here's a simple trick: pop the hood and feel the upper and lower radiator hoses. If the upper hose is scalding hot but the lower one remains cool, it likely indicates a faulty thermostat. Don’t delay fixing it—otherwise, engine overheating could damage the cylinder block, sending repair costs skyrocketing. I ended up solving it by replacing the part at a repair shop. Regular maintenance should include checking the coolant cleanliness to prevent such issues.
