Knock crankshaft main bearings
Such causes of knocking in main bearings are possible: insufficient oil pressure in the system, flywheel mounting bolts are loosened, increased clearances between the main necks and liners due to wear.
Knock connecting rod bearings
Excessive clearance between the bushings and connecting rod journals and insufficient oil pressure.
Knocking can be caused by the formation of carbon deposits on the walls of the combustion chambers or carbon deposits on the piston heads. The valves do not fit snugly to the valve medals.
Silent knocking. You are using low-quality fuel or a type of fuel that is not suitable for your vehicle. The ignition is not adjusted correctly. The formation of carbon in the combustion chambers. Failure of spark plugs or their mismatch.
The formation of carbon deposits on the pistons, valves, walls of the combustion chambers. Violation of the valve timing, the clearances in the valve mechanism are not adjusted.
Light engine noise
The drive chain is worn and loose. Chain tensioner failure. Damage to the valve spring. Deterioration of camshaft cams, loosening of adjusting bolt.
Such knocks can be heard without much effort, but for a better perception and accurate determination of the malfunction, you can use a stethoscope.
The sound of a hollow tone, the frequency of which depends on the number of revolutions of the crankshaft. If the sound of knocking is near the crankcase, it may be worn main bearings. The wear of the thrust rings of the crankshaft is accompanied by a sharp knock.
If you want to determine which connecting rod bearing is worn, then this can be determined by the sharp sound. This sound will be amplified with an increase in the number of revolutions of the crankshaft. The knock in the connecting rod bearings is determined by turning off the spark plugs one by one. Since the connecting rod in the cylinder does not work, it hangs without load and knocks louder.
Muffled, audible distinctly at low speeds of the crankshaft.
Knock piston fingers
Voiced and harsh sound, clearly audible at low speeds of the crankshaft.