What Causes Slow Engine Coolant Temperature Rise?
2 Answers
Slow engine coolant temperature rise may be caused by a malfunctioning thermostat. If the thermostat is damaged and causes the coolant to remain in the major circulation loop, it will result in slower engine temperature rise. In such cases, it is recommended to check whether the thermostat is functioning properly. Below is a detailed explanation: 1. Car engines rely on coolant for heat dissipation. During engine operation, the coolant continuously circulates within the engine to remove excess heat. The coolant follows two circulation paths inside the engine: a major circulation loop and a minor circulation loop. 2. When the engine is first started and the temperature is still low, the coolant circulates in the minor loop. During minor circulation, the coolant does not pass through the engine radiator for cooling, which helps the engine warm up quickly. Once the engine reaches normal operating temperature, the coolant switches to major circulation.
I've been driving for decades and often encounter situations where the engine temperature rises very slowly. The most common issue is a faulty thermostat. It's supposed to close the coolant circulation when the engine is cold to allow it to warm up, but if it gets stuck in the open position, the coolant immediately circulates through the radiator for cooling, preventing heat buildup. Another major problem is insufficient coolant or system leakage, which causes rapid heat loss. A malfunctioning fan control module or temperature sensor might also cause the fan to start cooling prematurely. This becomes more troublesome during short winter drives when the engine doesn't have enough time to warm up properly—it's normal occasionally but problematic if frequent. Low engine temperature affects fuel efficiency, increases fuel consumption, leads to insufficient engine lubrication, accelerates wear, and may even cause sludge buildup. I recommend first checking if the thermostat is functioning correctly, ensuring the coolant level is adequate and free of air bubbles. If any issues are found, visit a repair shop promptly for diagnosis to avoid further complications.
