Q: Fan never stops.

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Some times the fan starts and does not stop, it's sound like an airplane.

My car has 98777 miles.
My car has an automatic transmission.

Hey there, thank you for asking about your 2007 Mercedes-Benz CLK550. This is a common symptom of a failing coolant fan relay. This relay controls the cooling fans and cycles them on and off based upon temperature. When this relay is working intermittently or is faulty, it can cause the fans to come on randomly, come on and stay on, or sometimes not come on at all. This can be dangerous in the event they stop working altogether as it can cause the car to overheat. I would recommend having an expert from YourMechanic come to your home to diagnose the problem and replace the cooling fan relay if necessary.

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