What Causes Engine Noise in Cars?
3 Answers
Reasons for engine noise in cars: 1. If a rhythmic "ticking" sound comes from the upper part of the engine and its frequency increases with engine speed, this abnormal noise originates from the piston top hitting the cylinder head; 2. If "clanking" or "tapping" sounds are heard from the side of the engine block during operation, it indicates a cylinder knock fault; 3. Rough engine operation can, in extreme cases, cause connecting rod bending deformation. A bent connecting rod will deflect the direction of cylinder reciprocating motion, resulting in knocking sounds during piston movement reversal; 4. Excessive valve clearance can cause continuous "clicking" contact sounds around the cylinder head during cold engine operation. The frequency of this noise is directly proportional to engine speed but tends to diminish as the engine warms up.
A couple of days ago while driving, I heard a clicking sound from the engine and immediately pulled over. Based on my thirty years of driving experience, such abnormal noises mostly come from aging belts or worn water pump bearings, and a loose tensioner pulley can also cause a rattling sound. If there's a metallic knocking noise during a cold start, it's likely due to improperly adjusted valve clearance. With the recent heavy rainfall, a wet generator belt slipping can also produce a sharp squealing sound, which needs prompt attention to avoid a breakdown on the road.
Last time when repairing the car, the mechanic taught me how to identify abnormal engine noises: A gurgling sound may indicate insufficient engine oil causing dry friction in hydraulic lifters, while a metallic grinding noise often means the water pump bearing is failing. If there's a clicking sound during acceleration, the piston pin should be checked for looseness. When modifying my car, I found that a leaking exhaust pipe gasket produces a puffing sound. None of these abnormal noises should be ignored, and early inspection is crucial.
