What Causes the Engine to Make a Knocking Sound?

[DiKing]

Reasons for the engine making a knocking sound. Causes: Interruption or insufficient oil lubrication; loose connecting rod bearing cap bolts; excessive wear between bearings and shaft diameters; excessive clearance; bearing alloy welding detachment, etc. Knocking Sounds: Knocking sounds in the engine are mostly caused by abnormalities in the mechanical parts of the engine and are relatively serious abnormal noises. Common engine abnormal noises include piston knocking; crankshaft bearing knocking (big end bearing noise); connecting rod bearing knocking (small end bearing noise); piston pin knocking; valve tappet knocking, etc. Presence of Knocking Sounds: Simply running the engine can damage the crankshaft's connecting rod journals; if the engine speed and load are increased, the impact between the connecting rod bearings and the shaft diameters will become increasingly severe under the crankshaft's drive, leading to connecting rod bearing damage, loss of control of the connecting rod, cylinder block breakage, and ultimately engine failure.