Why does my Mercedes-Benz make a loud fan noise when the engine is running, even though it’s not overheating?

Steve Mowat

Steve Mowat

Steve Mowat, Owner of Avantgarde Automotive, began as a BMW apprentice in 1997, then excelled at McLaren and Mercedes-Benz. In 2009, he founded his business.

Identifying the Issue

Your Mercedes-Benz is a symbol of luxury and performance, and as an owner, you take pride in its upkeep. But a loud fan noise emanating from the engine can be worrisome, even if the engine isn’t overheating. Let’s explore some possible causes:

  • Worn-out or damaged fan clutch
  • Malfunctioning electric cooling fan
  • Loose or damaged fan belt

Possible Causes and Detailed Solutions

Worn-out or Damaged Fan Clutch

The fan clutch is responsible for regulating the speed of the cooling fan. If it’s worn out or damaged, the fan may run at full speed constantly, creating a loud noise.

To resolve this issue:

  1. Locate the fan clutch, usually found between the radiator and the engine.
  2. Inspect the fan clutch for visible signs of wear, such as cracks or leaks.
  3. If necessary, replace the fan clutch (part number A1132000222 for W212 E-Class).

Tools required: wrench set, torque wrench, and coolant drain pan.

Malfunctioning Electric Cooling Fan

Some Mercedes-Benz models, such as the W205 C-Class, feature an electric cooling fan. If it malfunctions, the fan may run excessively or constantly.

To fix this issue:

  1. Check the fan’s electrical connections and wiring for damage.
  2. Inspect the fan motor for signs of overheating or wear.
  3. Test the fan control module by connecting it to a diagnostic tool.
  4. If required, replace the faulty component (part number A0999062900 for W205 C-Class).

Tools required: multimeter, diagnostic tool, and screwdriver set.

Loose or Damaged Fan Belt

A loose or damaged fan belt can cause a loud fan noise. Here’s how to resolve it:

  1. Inspect the fan belt for cracks, fraying, or glazing.
  2. Check the belt tension; it should have about 10mm of deflection.
  3. If necessary, replace the fan belt (part number A0149979947 for W204 C-Class).

Tools required: wrench set, socket set, and belt tension gauge.

Regular Maintenance and Checks

Mechanic checking the underbody of a car in a workshop
Mercedes technician checking the underbody

To prevent fan noise issues, consider the following maintenance tips:

  • Schedule regular servicing with a Mercedes-Benz specialist.
  • Check the cooling system components for wear or damage during routine inspections.
  • Ensure proper coolant levels and monitor engine temperature.

When to Seek Professional Help

If you’re unable to resolve the fan noise issue or feel uncomfortable performing these tasks, it’s best to consult a Mercedes-Benz specialist. They have the expertise and equipment to diagnose and repair the problem efficiently.

Keep Your Mercedes-Benz Running Smoothly

By identifying the source of the fan noise and implementing the appropriate solutions, you can maintain the performance and luxury of your Mercedes-Benz. Remember, these tips and advice are offered as guidance, and the author cannot be held accountable for incorrect or out of date information.

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