Uploaded February 2024 | Updated September 2026, 4 hours ago

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A sound of a tensioner pulley rattling and going bad. Don't mistake this sound for rod knock. Rod knock varies with RPM, whereas tensioner pulley rattle can be random, or only occur when the car is warmed up as the belt stretches. You should not drive the car until you fix this.

Car in the video: BMW F30 N55 2013 - Tensioner Pulley Rattle, NOT Rod Knock. Same rattle can happen to any car with any kind of belt tensioner and pulley as the bearings or the tensioner itself is at the end of life.

What does a rod knock sound like? Watch the video.