3.14.1. Knocks in the engine

If it seemed to you that at engine work there were sounds which was not earlier, immediately check up, whether all is perfectly in order with the engine. More often knocks in the engine are connected with serious malfunctions, for diagnosing and which elimination it is necessary to assort the engine in the conditions of service or garage. However it is possible to try to define independently the reason of knocks to solve, go to car-care centre under the own steam or on a tow.

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

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

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

Knock of radical bearings (it is listened in the lowermost part of the block of cylinders) – very dangerous; stop immediately the engine, it is necessary to go to car-care centre or garage on a tow. Knock of low tone, considerably amplifies under loading and at increase in frequency of rotation of a cranked shaft. Its occurrence is frequent is accompanied by oil pressure drop (the alarm lamp of emergency pressure drop of oil burns almost constantly).

Knock шатунных bearings (it is listened in an average part of the block of cylinders) – very dangerous; stop immediately the engine, it is necessary to go to car-care centre or garage on a tow. A sound rhythmical, sonorous, metal, average tone. Considerably increases at increase in loading and completely vanishes at spark plug switching-off.

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-care centre or garage independently. Rhythmical, a high-pitch tone, with a sharp metal shade, it is audible on all power setting and amplifies at increase in loading at the engine. Completely vanishes at spark plug switching-off.

Knock of the worn out pistons and cylinders (it is listened in the same part of the engine, as knock of piston fingers) – harmless; without loading strongly the engine, it is possible to reach to car-care centre or garage independently. A sound reminding knock of pottery. It is especially well audible 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 cover of a head of the block) – harmless, it is possible to reach to car-care centre or garage independently. Metal knock against the general deaf noise. It is well listened on small and average frequency of rotation of a cranked shaft from outside heads of the block of cylinders over the locations of valves.

Detonation knocks — dangerous, but, as a rule, are eliminated by refuelling by qualitative fuel. Avoiding strong loading of the engine, it is possible to reach to car-care centre or garage independently. The sonorous metal knocks arising usually at dispersal of the car. The reason — wrong installation of the oktan-proof-reader, application низкооктанового fuel, an engine overload at too early inclusion of the raised transfer, considerable нагарообразование in combustion chambers. It is necessary to apply a special additive to fuel to deposit removal on valves and in combustion chambers.