What are the causes of abnormal noise when the Qashqai is running?

[AthenaLee]

The following are the reasons why the Qashqai produces a humming sound when running: 1. Worn tensioner pulley: The function of the tensioner pulley is to tighten the engine belt, ensuring that the generator and power steering pump do not slip. Due to prolonged pressure and high-speed rotation, the bearings inside the tensioner pulley are prone to wear, resulting in noise and resonance. If the humming sound and resonance are confirmed to be caused by the tensioner pulley, it is also necessary to check the engine mounts, as their role is to dampen the vibrations generated by the engine. 2. Deformed exhaust pipe: In most front-engine models, the exhaust pipe runs from the bottom of the car to the rear. Driving on rough roads or impacts to the undercarriage can easily cause the exhaust pipe to dent or deform. A deformed exhaust pipe increases exhaust resistance, leading to a humming sound. 3. Worn wheel hub bearing: The wheel hub bearing is installed in the suspension's "knuckle" and constantly bears the vehicle's weight and impacts during daily driving. The bearing balls inside are prone to wear, and the most typical symptom of a worn wheel hub bearing is a humming sound from the car.