What Causes Abnormal Noise in the Mercedes-Benz A200 Engine?
1 Answers
The causes of abnormal engine noise include premature fuel injection timing, diesel leakage from the injector, piston striking the cylinder wall, excessive piston ring side clearance, impact between the valve stem head and rocker arm, and engine misfire, among others. To determine the specific cause, it is necessary to analyze the different types of abnormal noise, as detailed below: Abnormal noise caused by rough engine operation, commonly known as "knocking sound." The symptoms include loud noise at low speeds, audible from a distance of several meters, accompanied by difficulty starting. After ignition, the engine runs unevenly, and coolant consumption is rapid. This noise is caused by premature fuel injection timing and requires readjustment of the fuel injection advance angle. Engine noise with a certain pattern, sometimes knocking, 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 "clunking" or "thudding" sound, particularly noticeable at low speeds or sudden speed changes, accompanied by oil burning. This noise is caused by excessive clearance between the piston and cylinder wall, which increases piston impact on the cylinder wall during operation. The solution is to replace the cylinder liner or piston. A "clinking" 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 and requires replacing the piston rings, and if necessary, the piston as well. A "clicking" or "tapping" sound around the cylinder head cover is 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. Exhaust gas flow shows obvious intermittency, accompanied by severe shaking of the exhaust pipe and clear engine noise. This is caused by engine misfire.
