What Causes Abnormal Noises in the Mercedes 272 Engine?
1 Answers
The causes of abnormal engine noises include premature fuel injection, 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 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, audible from a distance of over ten meters, accompanied by difficulty starting. After ignition, the engine runs unevenly, and coolant consumption is rapid. This noise is caused by premature fuel injection and requires readjustment of the fuel injection timing. Engine noise follows a certain pattern, sometimes knocking and sometimes backfiring, accompanied by unstable engine speed and intermittent black smoke emissions. This uneven noise is caused by diesel leakage from the injector. When this occurs, the injector should be serviced. The engine emits a "thudding" or "knocking" sound, particularly noticeable at low speeds or sudden speed changes, accompanied by oil burning. This noise is due to excessive clearance between the piston and cylinder wall, increasing piston impact against the cylinder wall during operation. The solution is to replace the cylinder liner or piston. A "clanging" sound resembling a small hammer lightly striking an anvil can be heard along the entire length of the cylinder block, becoming more pronounced during sudden speed changes. This is caused by excessive piston ring side clearance. The piston rings should be replaced, and the piston may also need replacement if necessary. A "clicking" or "tapping" sound around the cylinder head cover is quieter when the engine is warm but 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 flow shows obvious intermittency, accompanied by severe shaking of the exhaust pipe and clear engine noise. This is caused by engine misfire.
