What are the steps for testing a thermostat?
3 Answers
Thermostat testing steps: 1. At room temperature, manually push the large valve of the thermostat to the fully open position and secure it; 2. Install the thermostat with the large valve pushed open to the fully open position onto the thermostat seat and properly fit the thermostat cover; 3. Mount the thermostat assembly onto a simple test bench to measure the water pressure at the inlet and outlet of the thermostat and the flow rate in the small circulation pipe. A thermostat is a valve that controls the flow path of coolant, functioning as an automatic temperature-regulating device, typically containing a temperature-sensing component that opens or closes the flow of air, gas, or liquid through expansion or contraction. The thermostat automatically adjusts the amount of water entering the radiator based on the temperature of the cooling water, altering the water circulation range to regulate the cooling system's heat dissipation capacity, ensuring the engine operates within an appropriate temperature range.
With over a decade of experience in auto repair, here's how I test a thermostat: First, ensure the engine is completely cooled for safety. Remove the radiator cap to release pressure, then use a wrench to unscrew the thermostat housing bolts. After extracting the thermostat, prepare a basin of room-temperature water and submerge the thermostat in it. Gradually heat the water while monitoring the temperature changes with a thermometer. When the water reaches the thermostat's specified opening temperature (typically 82-90°C), the valve should begin to open. Continue heating to the full-open temperature (around 100°C) and check if the valve opening is sufficient. Don't forget to test the closing speed during cooling; it should fully close within 10 seconds. Always wear heat-resistant gloves throughout the process to avoid burns. Finally, inspect the valve edges for any scale buildup, as this is the most common cause of sticking.
Last time my car's coolant temperature was fluctuating, I checked the thermostat myself. Just prepare an old pot and a kitchen thermometer. When the engine is cold, remove the thermostat and boil it in a pot of cold water. Heat it while stirring, and the valve should slightly open around 85°C, fully opening at 95°C. Poke the valve with chopsticks to ensure it opens and closes smoothly without sticking. Pay special attention to the cooling process—the valve must close quickly as the temperature drops. When testing my old car, the valve's opening and closing were delayed by 3-4 seconds, so I replaced it immediately. The whole process took half an hour and saved me over 200 bucks compared to going to a repair shop. When washing your car, feel the temperature difference between the upper and lower radiator hoses—if it's too small, the thermostat might be stuck open.
