What Causes Engine Abnormal Noises?
2 Answers
The causes of abnormal engine noises include premature fuel injection timing, diesel leakage from the injector, piston impact against the cylinder wall, excessive piston ring side clearance, impact between the valve stem head and rocker arm, and engine misfire. The specific cause needs to be determined based on different abnormal noise conditions, as detailed below: Abnormal noise caused by rough engine operation, commonly known as "knocking sound." The phenomenon is characterized by strong noise at low speeds, which can be clearly heard from a distance of over ten meters from the engine, accompanied by difficulty in starting. After the engine starts, it runs unevenly, and coolant consumption is rapid. This abnormal noise is caused by premature fuel injection timing and requires readjustment of the fuel injection advance angle. Engine abnormal noise has a certain pattern, sometimes knocking, sometimes backfiring, accompanied by unstable engine speed and intermittent black smoke emissions. This uneven abnormal noise is caused by diesel leakage from the injector. When this phenomenon occurs, the injector should be serviced. The engine emits a "thud," "thud" knocking sound, which is particularly noticeable at low speeds or sudden changes in engine speed, accompanied by burning engine oil. This abnormal noise is caused by excessive clearance between the piston and cylinder wall, increasing piston impact against the cylinder wall during diesel engine operation. The solution is to replace the cylinder liner or piston. A "clang," "clang" sound similar to a small hammer lightly striking an anvil can be heard along the entire length of the cylinder block, becoming more pronounced with sudden changes in engine speed. This is caused by excessive piston ring side clearance. The piston rings should be replaced, and if necessary, the piston should also be replaced. "Click," "click" knocking sounds around the cylinder head cover are quieter when the engine is warm and louder when cold, persisting even when fuel supply is stopped at low speeds. The main cause is excessive valve clearance, leading to impact between the valve stem head and rocker arm. The valve clearance should be adjusted. The exhaust gas flow from the car shows obvious intermittency, accompanied by severe shaking of the exhaust pipe and clear abnormal engine noise. This abnormal noise is caused by engine misfire.
As someone who has driven for many years, I've encountered various engine noise issues. There are quite a few causes: the most common is a loose or worn belt making squeaking sounds, especially noticeable during acceleration; a loose chain can produce similar noises. Listen to the source of the sound—clicking noises are often caused by excessive valve clearance or low oil pressure; heavy knocking sounds might indicate connecting rod wear. Older vehicles are prone to bearing noises, which sound like dry grinding. Additionally, insufficient or dirty oil leading to inadequate lubrication can easily cause abnormal noises, so it's advisable to develop a habit of regularly checking oil levels. Ignoring these small sounds could lead to major failures, such as piston fractures. Therefore, upon noticing any unusual noises, it's best to drive to a repair shop for a check-up without hesitating over time or cost.
