What Causes Abnormal Noise When Starting the Engine?
2 Answers
When starting the vehicle, the reasons for abnormal engine noise include: 1. Premature connection of the electromagnetic switch main contacts: The starter makes abnormal noise when the starter drive gear has not yet engaged with the flywheel ring gear. 2. Poor contact of the electromagnetic switch: The rotor collides with the magnetic pole, the brushes are excessively worn, or the electromagnetic switch has poor contact. 3. Drive gear failure to disengage: The drive gear fails to disengage and continues to operate. Even after turning off the ignition switch and cutting off the power, the starter still runs, and a screeching sound occurs immediately after the engine starts. The starter is dragged at high speed and cannot stop or takes a long time to stop, causing the starter to sweep and burn out.
I've encountered the issue of abnormal noises during engine startup many times, and there are quite a few common causes. For example, worn starter gears or faulty solenoid switches can produce a metallic grinding sound, which is particularly common in vehicles over five years old. Belt aging is another key factor, especially the alternator belt - once it hardens and cracks, it will produce a squeaking sound. If the timing chain becomes loose, there will be obvious metallic knocking sounds during startup. The most easily overlooked issue is the engine mount rubber - when this rubber component ages, it causes engine vibrations to transfer to the frame, creating a buzzing resonance. I recommend first identifying when and where the noise occurs - if it's louder during cold starts, prioritize checking the belts and starter. Also, pay attention to oil levels during maintenance, as insufficient lubrication can cause abnormal sounds from the valve lifters. It's best to have it diagnosed at a professional repair shop as soon as possible - don't wait until the noise becomes increasingly severe before addressing it.
