What are the symptoms of abnormal engine noises?
2 Answers
There are many reasons for abnormal engine noises, such as piston slapping, piston pin noise, crankshaft main bearing noise, etc. The details are as follows: 1. Piston slapping noise: Phenomenon: A dull, rhythmic "da da" sound can be heard in the car, which is clearer when the engine is cold and idling, and significantly weakens or even disappears after the engine warms up. 2. Piston pin noise: Phenomenon: A crisp, sharp, and continuous "to to" sound, like two steel balls colliding, can be heard in the piston movement area of the engine. The noise is more noticeable when the engine is idling or at low to medium speeds, intensifies with throttle input, and the rhythm speeds up. The noise weakens or disappears when a single cylinder is cut off. 3. Crankshaft main bearing noise: Phenomenon: A heavy "dang dang" metal knocking sound can be heard in the crankcase area. The noise is rhythmic and increases with higher engine speed and load. Cutting off a single cylinder does not significantly change the noise, but cutting off two adjacent cylinders weakens the noise. The "da da" noise from the engine is a relatively common type of abnormal engine noise. Sometimes, after changing the engine oil, especially when switching to a higher viscosity oil, the "da da" sound may become noticeably audible. This is mostly caused by increased internal resistance due to higher viscosity and generally does not significantly affect the engine. However, if the hydraulic lifters are malfunctioning, they often produce a "da da" noise. Hydraulic lifters are designed to automatically eliminate valve clearance and reduce engine noise. But once they fail, they can cause a more severe "da da" noise in the engine.
When my car's engine makes strange noises, there are quite a few symptoms. Upon starting the car, sometimes I hear a sound like drum beats, which might indicate valve issues; when accelerating, it turns into a high-pitched screech, like wind whistling through a crack, most likely due to aged or loose belts. If the sound fluctuates in intensity while driving, it could be misfiring or lubrication problems—I often record these sounds with my phone to show the mechanic. If not addressed promptly, the engine might overheat or worse, and repair costs can skyrocket. I remember last time when my car was humming and I ignored it, it ended up stalling, costing me thousands to replace parts. In short, strange noises are not minor issues—get them checked at the garage at the first sign, safety first.
