What Causes a Mercedes-Benz to Frequently Run at Low Speed with Normal Water Temperature?
2 Answers
Mercedes-Benz frequently running at low speed with normal water temperature is caused by issues such as the water pump impeller coming off the shaft, water pump damage, cooling system blockage, or water temperature sensor failure. Water Pump Damage: The coolant circulates through the water pump. If the water pump is damaged, the coolant essentially loses its function, and the heat generated by engine combustion cannot be dissipated. Insufficient Coolant: It is common knowledge among car owners that insufficient coolant leads to increased water temperature. However, using water or substandard, unqualified coolant as a cooling medium can also cause the engine temperature to rise excessively. Thermostat Damage: When the thermostat is damaged or stuck, the engine operates with only a minimal coolant circulation, and the radiator fails to dissipate heat effectively. This results in low cooling intensity, leading to high engine temperature.
In my experience, it's quite common for Mercedes-Benz vehicles to have normal coolant temperature but frequently experience unstable idle speeds at low speeds. This is mostly caused by carbon buildup in the throttle body. When the engine runs at low speeds, carbon deposits block the intake passages, causing poor airflow. The sensors misread data, leading the ECU to control idle speed unstably. Worn spark plugs can also cause unstable ignition, and clogged fuel injectors are often to blame as well. I've encountered many Mercedes owners whose engines would surge erratically in traffic jams - cleaning the throttle body and checking the mass airflow sensor usually solves the problem. Additionally, if the oxygen sensor is dirty or faulty, it may send incorrect signals, creating circulation issues. I recommend regular maintenance of the intake and exhaust systems, along with cleaning components to prevent worsening carbon buildup. These minor issues can accumulate and affect engine longevity, so it's best to have them addressed promptly at a specialized repair shop.
