What Causes Low Engine Coolant Temperature?
2 Answers
Low engine coolant temperature in vehicles is typically caused by a faulty thermostat or abnormal radiator fan operation. Generally, the normal operating temperature for most vehicles is around 90 degrees Celsius, though this may vary slightly between different car brands. The engine requires a specific operating temperature to function properly, and both excessively high and low temperatures can adversely affect engine performance. Faulty Thermostat: The thermostat regulates engine temperature based on coolant temperature. If the thermostat malfunctions and fails to close, coolant will continuously circulate through the large cooling circuit, potentially causing the engine to run too cold. Some owners remove the thermostat during summer to lower temperatures, which also results in abnormally low engine temperatures. Solution: After starting the engine, check for coolant flow in the radiator; inspect whether water flows through the radiator inlet hose; monitor the temperature gauge for abnormal readings. Abnormal Radiator Fan Operation: If electrical issues cause the cooling fan to run continuously, it will reduce the warming efficiency of both the engine and coolant, resulting in slow temperature rise and significantly increased fuel consumption. During cold starts, observe whether the fan is running (without turning on the AC) to help diagnose the issue. After ruling out sensor failure and radiator fan malfunction, persistent abnormal temperatures usually indicate thermostat problems. Solution: Professional repair shop service is recommended.
As an experienced automotive repair technician, I often encounter situations where the car's coolant temperature is too low. The most common cause is a thermostat stuck in the open position, which means the coolant flows into the radiator too early, dissipating heat too quickly and preventing the engine from reaching optimal operating temperature. This issue is more likely to occur in older vehicles or during frequent cold starts in winter, often due to thermostat aging or dust blockage. Additionally, insufficient coolant level is another common reason, such as leaks causing coolant loss. Faulty temperature sensors or abnormal operation of the fan control system can also mistakenly accelerate cooling. Low coolant temperature can significantly harm the engine—it lowers oil temperature, reduces lubrication effectiveness (accelerating component wear), and may even increase fuel consumption. I recommend car owners regularly check thermostat functionality, use the correct coolant specification during changes, and monitor whether the temperature gauge rises normally after each startup. If any issues are detected, seek professional repair services promptly to avoid major problems. Regular maintenance, including cleaning the cooling system, is also highly beneficial.
