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Stan, Mercedes Technician
Category: Mercedes
Satisfied Customers: 3526
Experience:  Technical support engineer
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Hi i have a mercedes c200 blue-cy exec secdi a 2011 diesel

Customer Question

Hi i have a mercedes c200 blue-cy exec secdi a 2011 diesel
Sometimes as im driving the engine makes a very loud humming noise ( sounds like a small aeroplane ). ! Im in cyprus in 35 degrees heat with the aircon on so i turned off the aircon thinking its that but still makes noise. When im driving its very loud. When car stops at lights then you can hear noise declining. Took it to a garage here and they said it must be the blower. What does this mean and what should i do ??
Would appreciate expert mercedes advice
Submitted: 3 years ago.
Category: Mercedes
Expert:  Shantal-Mod replied 3 years ago.

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Expert:  Stan replied 3 years ago.
The engine and air conditioning cooling fans will make a lot of noise in the 35 degree heat, that is normal. I would recommend to make a test drive with a workshop foreman or technician so that they could also hear the same noise in driving situation. If they confirm that the properly running fans and blowers are causing this- you have nothing to worry about.
Also, there should be no fan noise when the engine is started from cold with AC off.
Fans only work when engine temp is above 80 degrees and AC is on
Customer: replied 3 years ago.
Thanks for the info. Just to clarify that sometimes there is a noise when started from cold even with aircon off.
Not always though !
Any ideas why?