Hi, my name is***** many miles are on the Mercedes? Can you post the last 8 digits of the vin number?
Okay, actual timing chain failure on this motor is not common, especially if there is no check engine light illuminated. What is more common is a failure of the balance shaft in the motor. When the balance shaft fails it causes the check engine light to come on and will store fault codes for the camshaft timing. If there is no check engine light I suspect that the rattling noise is coming from outside the motor in the area of the serpentine belt or belt tensioner. I would suggest removing the belt as a test to see if the rattling noise goes away. If it does then your problem is outside the motor with one of the rotating components.
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