3.14.1. Knocks in the engine

If it seemed to you that during the operation of the engine there were sounds which were not earlier, immediately check, 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.

Fig. 3.1. Zones of listening of knocks in the engine: 1 – radical bearings; 2 – conrod bearings; 3 – piston fingers; 4 – pistons; 5 – valves

Zones of listening of knocks are shown in fig. 3.1.

PREVENTION If you have slightest doubts in results of 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 (it is listened in the most lower part of the block of cylinders) – very dangerous; stop immediately the engine, it is necessary to go to car service or a garage on the tow. The knock of low tone, considerably amplifies under loading and at increase in frequency of rotation of a bent shaft. 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 (it is listened in a middle part of the block of cylinders) – very dangerous; stop immediately the engine, it is necessary 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 (it is listened in the top part of the block of cylinders) – 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 (the knock of piston fingers is listened in the same part of the engine, as) – 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 (it is listened in the top part of the engine around a block head cover) – 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.

Detonation knocks — dangerous, but, as a rule, are eliminated with filling with qualitative fuel. Avoiding strong loading of the engine, it is possible to reach to car service or a garage independently. The ringing metal knocks arising usually at dispersal of the car. The reason — the wrong installation an octane proofreader, 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 apply special additive to fuel to removal of a deposit on valves and in combustion chambers.