WARNING: If you have the slightest doubt about self-diagnosis, remove the tow rope. Serious repairs to a damaged engine will cost more than the services of a towing vehicle.
Knock of main bearings bugged at the very bottom of the cylinder block - very dangerous; stop the engine immediately, you will have to go to a car service or garage in tow. A low-pitched knock that increases noticeably under load and with an increase in the crankshaft speed. Often its appearance is accompanied by a drop in oil pressure (The oil pressure warning light is almost permanently on).
Knocking rod bearings bugged in the middle part of the cylinder block - very dangerous; stop the engine immediately, you will have to go to a car service or garage in tow. The sound is rhythmic, ringing, metallic, medium tone. Significantly increases with increasing load and completely disappears when the spark plug is turned off.
Knock of piston pins bugged in the upper part of the cylinder block - dangerous; without loading the engine, you can drive to a car service or garage on your own. The sound is rhythmic, high-pitched with a sharp metallic tint, audible in all engine operating modes and intensifies with increasing engine load. Completely disappears when the spark plug is turned off.
The sound of worn pistons and cylinders audible in the same part of the engine as the sound of piston pins - not dangerous; without heavily loading the engine, you can drive to a car service or garage on your own. A sound reminiscent of the clatter of pottery. It is especially well heard on a cold engine, as it warms up it decreases or disappears.
Valve knock audible in the upper part of the engine in the area of \u200b\u200bthe head cover - it is not dangerous, you can drive to a car service or garage on your own. A metallic thump against the background of a general muffled noise. It is well audible at low and medium speeds of the crankshaft from the side of the cylinder head above the valve locations.
detonation knocks - Dangerous, but usually eliminated by replacing the knock sensor or filling with good quality fuel. Avoiding a strong engine load, you can drive to a car service or garage on your own. Voiced metallic knocks that occur, as a rule, during acceleration of the car. The reason is the failure of the knock sensor, the use of low-octane fuel, engine overload with too early upshift, significant carbon formation in the combustion chambers. It is necessary to apply a special fuel additive to remove carbon deposits on valves and in combustion chambers.