What are the methods for checking the thermostat?
2 Answers
Here are several methods for checking the car thermostat: 1. Inspection after engine start: Open the radiator filler cap. If the coolant in the radiator is calm, it indicates the thermostat is working properly; otherwise, it indicates malfunction. When the coolant temperature gauge shows below 70°C, if there is coolant flow at the radiator inlet pipe and the coolant is warm, it means the thermostat's main valve is not tightly closed, causing premature major coolant circulation. 2. Inspection after coolant temperature rises: In the early stage of engine operation, the coolant temperature rises rapidly. When the temperature gauge indicates 80°C, if the temperature rise slows down, it indicates the thermostat is functioning normally. When the coolant temperature gauge shows 70-80°C, open the radiator cap and drain valve, and feel the coolant temperature by hand. If both feel hot, the thermostat is working properly. If the coolant temperature at the radiator filler is low, and there is little or no coolant flow at the radiator upper tank inlet pipe, it means the thermostat's main valve cannot open.
I did thorough research on thermostat inspection right after replacing mine. After starting the engine, simply feel the temperature of upper and lower radiator hoses. If the upper hose gets scalding hot after 10 minutes of cold start while the lower hose remains cold, the thermostat is likely stuck closed. Be alert if the temperature gauge struggles to reach midpoint - I encountered this last winter. Another crude method is boiling the removed thermostat in water; it should gradually open around 80°C, but remember to measure if the opening gap reaches 8mm. Electronic thermostats are trickiest, requiring an OBD scanner to read coolant temperature data stream - I specifically bought a diagnostic tool for this. Actually, heater performance helps too - poor cabin heat often indicates thermostat issues, a trick that's saved me three towing fees.
