the fan can fail in a permanently engaged position, that usually occurs when either the silicone oil has turned to a black gel or the bearing has siezed.

In any case do not drive around like that, take the fan off or replace it. btw - the fan can roar at even 60C on the gauge if its summer and the A/C is on. The heat from the condenser can cause the fan to work.

To test - start the engine dead cold, pop the hood accelerate engine, the fan should roar at first then would decouple from the engine in about 3 or 4 seconds.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)