Why does the Mercedes-Benz display a coolant refill prompt when the coolant level is normal?
3 Answers
The reasons why a Mercedes-Benz shows a coolant refill prompt when the coolant level is normal are as follows: 1. High coolant temperature: The driver should immediately find a suitable location to stop and observe. If the water temperature is high, the engine should be shut off immediately. After allowing it to cool for a while, contact a repair facility as soon as possible for inspection and maintenance. Note that if the engine is experiencing excessively high water temperature, do not continue driving, as this risks damaging the engine. 2. The signal transmitted by the vehicle system indicates low coolant level: If it is confirmed that the coolant level is normal and the engine water temperature is also normal, the alarm is likely caused by incorrect coolant level or water temperature signals. In this case, it is necessary to check whether the sensors and wiring are functioning properly and whether the control unit's program has any errors.
I've been driving a Mercedes for many years, and this issue is actually quite common. It's most likely the fluid level sensor acting up. The sensor might be stuck in the wrong position due to dirt or aging, falsely reporting insufficient coolant. Mercedes' electronic systems are quite sophisticated and can be prone to false alarms from bumps or temperature changes. Loose wiring connections or short circuits can also cause this. If the coolant level is indeed fine, don't panic right away. Try turning the engine off and restarting it a few times to see if the warning disappears. If it persists, it's best to get it checked at an authorized dealership to prevent a minor issue from turning into a major repair. Remember to clean the sensor area during regular maintenance to avoid dust buildup, which can help reduce such false alarms.
Last time my car also had this warning, the coolant was full but it kept prompting me to refill, so annoying. I suspect it's a sensor or wiring issue, since the sensor might not be detecting the correct fluid level, or the wires could be corroded or disconnected. You can do a quick visual check yourself—look for cracks or leaks in the coolant reservoir and make sure the connections aren’t loose. Mercedes has a unique design where the sensor is inside the reservoir, so cleaning it requires some technical skill. If you’re not confident in your DIY abilities, don’t force it. Get it checked at a professional repair shop early to diagnose the electrical circuit and prevent engine overheating or breakdown. For safety, don’t ignore these small warnings—regular maintenance saves hassle later.
