What Causes the Abnormal Noise During Car Startup That Disappears Later?
2 Answers
Reasons for abnormal engine noise when starting the vehicle: Early engagement of the electromagnetic switch main contacts: When the starter drive gear has not yet engaged with the flywheel ring gear, the starter emits abnormal noise. Poor contact of the electromagnetic switch: The rotor collides with the magnetic poles, the brushes are excessively worn, or the electromagnetic switch has poor contact. Failure of the drive gear to disengage: If the drive gear fails to disengage and continues to operate, the starter keeps running even after turning off the ignition switch and cutting the power supply. A screeching noise occurs immediately after the engine starts. The starter is dragged at high speed and cannot stop or takes a long time to stop, leading to starter drag and burn.
I used to encounter this situation often when repairing cars - the vehicle would make a strange squeaking noise upon startup that quickly disappeared. Usually, it's an issue with the alternator belt or AC belt. When starting in cold weather, the stiff belt combined with a loose or aged tensioner causes belt slippage and noise, which goes away once the engine warms up. It could also be worn water pump bearings making friction noise at startup that quiets down after lubrication. Don't delay repairs - a broken belt can cut power, cause the alternator to fail, and leave your car stranded. I recommend regular checks of belt tension and small components. Replacing a belt costs less than 100 yuan - it's both convenient and safe.
