Knocking in the engine: causes and consequences
Every motorist occasionally has to hear knocking while the engine is running. What causes these sounds and can you determine by hearing which part is out of order?
As a rule, a knock in the engine with normallubrication and cooling occurs due to the fact that the gap between the parts in the joint increases. Usually, this sound is clearly audible when the gap becomes approximately three times the nominal size. As the clearance increases, the wear rate of the engine parts increases, and the clatter becomes louder.
Sometimes there is a situation when thethe motor also occurs at a normal gap size. In this case, it can be caused by such reasons as heavy loads on the engine, skewing and jamming of one of the parts, reducing the viscosity of the oil due to overheating or dilution with another liquid (for example, when fuel enters the oil).
Determine by sound
We will make a reservation at once - to define knocking in the engine on hearing at times very uneasy even to the motorist with the experience. But the general laws still exist.
If the knock appears regularly, it is worthTest the engine in different modes. As is known, the parameters of the engine operating mode are the crankshaft speed and the load, which increases as the throttle is opened. If, with an increase in the engine speed, the sound amplifies, then, most likely, problems should be sought in the piston group and the gas distribution mechanism.
As the load increases, the pressure in thecylinders and, correspondingly, the load on the moving parts of the engine - first of all, the piston group - increases. Therefore, in the presence of defects in the crank mechanism, the knock in the engine increases as the load increases.
Now let's try to determine the "knocking" part bytone knock. If, while the engine is running at idle speed, you hear a thud, which then, as the number of revolutions increases, becomes louder and more frequent, then the crankshaft is knocked, where the crankshaft bearings or main bearings are worn. The reason may be an untimely change of oil or oil filter.
A dull thud in the engine "on the cold", that isat start of the cold engine, can testify about deterioration of bearings of a camshaft. As a rule, such a knock lasts not more than a couple of seconds, until oil falls on the bearings. If the knock then disappears, then with such a camshaft you can still drive up to 50,000 km. Later, the knock becomes more audible even when a warm engine is started, and neglecting the engine results in increased fuel consumption, deterioration of the starting qualities of the power unit, and deposits on the valve seat. The reason for the wear of the camshaft bearings may be poor oil quality, bearing operation in the absence of oil or lack of it, oil or impurities entering the oil.
A light metal knock on the engine,arising when the revolutions increase, may indicate detonation. This is the name of the phenomenon in which fuel burns hundreds of times faster than under normal conditions. When detonation occurs shock wave, which during the movement of the piston down tens of times is reflected from the piston and cylinder head, while causing the same knock. In addition to knocking, detonation can be indicated by a drop in engine power, shaking of the unit during operation, overheating of the cylinder head. The reason for the detonation is the use of low-octane fuel, the formation of carbon deposits in the combustion chamber, the failure of the exhaust gas recirculation valve. The result of detonation is the damage to the pistons and piston rings.