Overheating a BMW can damage the head gasket, the cylinder head, or both. Stop driving immediately if the gauge climbs into the red zone or you see steam.
Common BMW cooling system failures
Plastic expansion tanks crack with age and heat, often around the seams or the cap.
Water pumps wear bearings or fail electrically on N-series engines.
Thermostats stick open or closed, which trips warning lights and changes operating temperature.
Hoses, O-rings, and oil filter housings can leak coolant in places that look like the source but are downstream of a different failure.
Warning signs
Coolant warning message in the iDrive screen.
Temperature gauge moving higher than normal in traffic.
Low coolant warning shortly after a recent top-off.
Sweet smell or steam under the hood.
What to do
Stop driving safely if the gauge is in the red or steam is visible.
Do not open the radiator or expansion tank cap while hot.
Call AAB Service or arrange a tow rather than risk head gasket damage.
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