What Causes Low Engine Coolant Temperature?
2 Answers
Low coolant temperature can be caused by the following reasons: 1. The thermostat, which acts as a valve component based on engine coolant temperature, is installed at the radiator outlet and water pump inlet. When the coolant temperature is low, the thermostat blocks the low-temperature coolant from the radiator, preventing it from entering the engine water jacket, allowing the water jacket temperature to rise quickly. When the coolant temperature reaches a certain level, the valve opens, allowing coolant from the radiator to circulate, slowly increasing the coolant temperature as it flows through the radiator, dissipating heat to the atmosphere and maintaining the engine at an appropriate temperature—this is known as the major circulation. If the thermostat malfunctions and the valve fails to close, the coolant remains in major circulation, potentially causing the engine temperature to be too low. Alternatively, some vehicles may have their thermostats removed during summer to reduce high temperatures, which can also result in very low engine coolant temperatures. 2. Electrical faults causing the electric fan to run continuously, or failure of the silicone fluid fan or silicone fluid clutch, can lead to constant fan operation.
I've encountered low engine coolant temperature quite often, mostly due to the thermostat stuck in the open position, causing the coolant to keep circulating in the large loop, preventing the engine from warming up properly. Sometimes the coolant temperature sensor fails, constantly reporting low temperature even when the engine is warm, especially noticeable in winter when using the heater. The cooling fan might also keep running non-stop - designed to cool the engine but blowing away all the heat in cold weather, making it impossible for the temperature to rise. I once experienced this during a long-distance drive in freezing weather where the temperature stayed below 60°C, with terrible fuel consumption. After inspection, we found the thermostat spring had loosened. Spending a few hundred to replace it fixed the issue. Now I regularly check the dashboard to ensure proper engine warm-up, otherwise the engine runs inefficiently, causing vibrations and high fuel consumption.