What Causes the Engine Water Temperature to Get Lower While Driving?
2 Answers
Engine water temperature getting lower while driving may be caused by the thermostat opening too early or staying open, or the electric fan running continuously. Thermostat opening too early or staying open: If the thermostat malfunctions, such as staying open or opening too early, it will cause the coolant to flow through the radiator too early and participate in the large circulation. After being cooled by the electric fan, the water temperature will remain in the low-temperature range. Electric fan running continuously: The electric fan is usually installed near the radiator and closely attached to it to cool the coolant inside the radiator. If the electric fan remains in the on state, it is similar to the thermostat staying open, causing the water temperature to be cooled by the electric fan before it can rise, preventing the engine water temperature from increasing.
As an enthusiastic car enthusiast, I've noticed that the issue of engine coolant temperature dropping while driving is actually quite common. The main cause is a thermostat stuck in the open position - that component is supposed to stay closed when the engine is cold to allow quick warm-up, but when stuck open, it keeps circulating coolant through the radiator for cooling. A faulty temperature sensor can also give false low-temperature readings. Chronically low coolant temperature is no minor matter - when the engine doesn't reach its optimal operating temperature around 90°C, incomplete combustion can increase fuel consumption by over 5%, while poor oil lubrication accelerates internal component wear, potentially leading to major repairs long-term. This problem becomes more noticeable in winter when cold air blowing through the radiator causes rapid temperature drops. I recommend having a professional shop check the thermostat and sensor promptly to prevent minor issues from escalating into major ones.