3.11.1. Knocks in the engine

If it seemed to you that during the operation of the engine there were sounds which were not earlier, be immediately convinced, whether all as it should be with the engine. Most often knocks in the engine are connected with serious malfunctions for which diagnosing and elimination it is necessary to disassemble the engine in the conditions of service or a garage. However it is possible to try to define independently the reason of knocks to solve, go to car service under the own steam or on the tow.

Prevention
If you have slightest doubts in independent diagnostics, get a towing cable. Serious repair of the damaged engine will be more expensive, than services of a tower.

Knock of radical bearings — very dangerous; to stop the motor immediately, it is necessary to go to car service or a garage on the tow. Knock of low tone. It is listened in the lower part of a case, considerably amplifies under loading and at increase in frequency of rotation. Often its emergence is followed by oil pressure drop (the alarm lamp of emergency pressure drop of oil burns almost constantly).
Knock of conrod bearings — very dangerous; to stop the motor immediately, to go to car service or a garage on the tow. The sound is rhythmical, ringing, metal, average tone. Considerably increases at increase in loading and completely vanishes at shutdown of a spark plug.
Knock of piston fingers — dangerous; without loading the engine, it is possible to reach to car service or a garage independently. Rhythmical, high-pitch tone, with a sharp metal shade, it is heard on all power setting and amplifies at increase in load of the engine. Completely vanishes at shutdown of a spark plug.
Knock of worn-out pistons and cylinders — harmless; without loading strongly the engine, it is possible to reach to car service or a garage independently. The sound reminding knock of pottery. It is especially well heard on not heated-up engine, in process of warming up decreases or disappears.
Knock of valves — harmless, it is possible to reach to car service or a garage independently. Metal knock against the background of the general deaf noise. It is well listened at a small and average frequency of rotation of a bent shaft from a head of the block of cylinders over the locations of valves. The knock of valves usually appears at failure of hydrocompensators which in this case need to be replaced.
Detonation knocks — dangerous, but, as a rule, are eliminated with replacement of the sensor of a detonation. Without loading strongly the engine, it is possible to reach to car service or a garage independently. The ringing metal knocks arising, as a rule, at dispersal of the car. The reason — failure of the sensor of a detonation, use of low-octane fuel, an engine overload at too early inclusion of an overgear, a considerable nagaroobrazovaniye in combustion chambers. It is necessary to replace the detonation sensor (see section 10 "Electric equipment") and to apply special additive to fuel to removal of a deposit on valves and in combustion chambers.