Why does the BMW 5 Series fan keep running?

[Reid]

BMW 5 Series fan keeps running because in summer when the ambient temperature is higher, the electric fan needs to operate at a higher speed compared to other seasons to dissipate the heat generated by the radiator. When the air conditioning is turned on, the electric fan is required to operate. When the water temperature continues to rise, the fan needs to run at an even higher speed to ensure proper air conditioning cooling and normal engine operating temperature, which naturally makes the fan noise louder. The car radiator, also known as the heat exchanger, is a key component in the car's cooling system. Its function is to dissipate heat. The coolant absorbs heat in the water jacket, flows to the radiator to release the heat, and then returns to the water jacket to circulate, achieving temperature regulation. It is an integral part of the car engine. The BMW 5 Series has body dimensions of 5087mm in length, 1868mm in width, and 1500mm in height, with a wheelbase of 3108mm.

[EverlyLynn]

I've encountered this issue before, which is quite common. When a BMW's fan keeps running non-stop, it's usually the cooling system working overtime. First, check if the coolant level is low—this is something you can easily inspect yourself. Another possibility is a faulty coolant temperature sensor; it might falsely indicate high temperatures, causing the fan to run excessively. Sometimes, a stuck thermostat that fails to open can also cause this issue, leading to poor coolant circulation. Additionally, prolonged traffic jams or heavy loads when using the air conditioning can make the fan run longer. However, if the fan continues to spin after the engine is turned off, it’s definitely an electrical fault or a control module issue. Don’t ignore it—engine overheating can lead to serious damage. It’s best to visit a dealership as soon as possible to read the fault codes and diagnose the problem. Last time, mine turned out to be a loose sensor connector causing all the trouble.

[StLuna]

As a long-time BMW owner, continuous fan operation usually indicates high cooling demand. The most likely cause is a cooling system issue, such as a clogged radiator reducing heat dissipation efficiency, or a malfunctioning water pump. High pressure in the AC system can also force the fan to run—try turning off the AC. For electrical aspects, check if the fan relay is stuck—this component frequently fails. During repairs, I've also seen abnormal high temperatures caused by a faulty crankcase ventilation valve. If it happens after parking, it's probably the engine control unit releasing residual heat, but exceeding five minutes isn't normal. The dashboard coolant temperature light not being on doesn't mean everything's fine; it's best to check real-time data streams with a diagnostic computer.

[StAsher]

Persistent fan operation should be analyzed from three aspects. Physically: Dust accumulation on heat sinks or bearing jamming causing mechanical resistance. Electrically: ECU misinterpreting temperature signals, often due to aging coolant temperature sensors or wiring. System-wise: Overly high AC refrigerant pressure triggering protection mechanisms. If the engine bay was recently washed, potential short circuits from water ingress in connectors. Quick check: Feel coolant hose temperature when cold, inspect radiator surface for obstructions. However, BMW's intelligent thermal management is complex—I advise against DIY disassembly to avoid interfering with active grille shutters, which could compound issues.