Knock on the engine: Causes and Consequences

every motorist from time to time we hear a knock during engine operation.What caused these sounds and can we identify by ear exactly which part is out of order?

Common causes

As a rule, the sound of the engine at normal lubrication and cooling occurs due to the fact that between the parts that are in the mix, increase the gap.Normally this sound is heard well, when the gap becomes approximately three times the nominal value.As soon as the gap increases, the rate of engine wear increases and the knock gets louder.

Sometimes there is a situation when there is a knock on the engine and under normal largest gap.In this case, it can be caused by factors such as large engine load, misalignment and jamming one of the parts, reducing the viscosity of oil due to overheating or dilution with another liquid (e.g., when the fuel enters the oil).

is determined by the sound

Say at once - to determine engine knock in the ear sometimes very difficult, even with the experience minder.But general laws still


If there is a knock on a regular basis, it is necessary to test the engine in various modes.As is known, the parameters of the engine operating condition is engine speed and load, which increases as the throttle opening.If an increase in the number of revolutions of the engine sound is amplified, then most likely, the problem should be sought in the plunger and the timing.

With increasing load increases the pressure in the cylinders and therefore increases the load on the moving parts of the engine - especially piston group.Therefore, the presence of defects in the crank mechanism of a knock in the engine grows stronger as the load increases.

Now let's try to define the "pounding" item on the pitch knocking.If the engine is idling, you hear a thud, which then with increasing speed, becoming louder and more often, it "knocks" the crankshaft, which inserts worn connecting rod or main bearing or shaft journal.The reason may be delayed oil change or oil filter.

thud in the engine "in the cold", that is when you start a cold engine, may indicate deterioration of the bearings of the camshaft.Typically, such a knock lasts no more than a couple of seconds until the oil gets on the bearings.If a knock then disappears with the camshaft it is still possible to travel up to 50,000 km.Later knock becomes audible even when starting a warm engine, and the lack of attention to the motor leads to the fact that increases fuel consumption, deteriorating the quality of starting the power unit, and is the deposition of carbon on the valve seat.The cause of the wear of the camshaft bearings may be of poor quality oil of bearings with a lack of oil, or the absence thereof, from entering the oil or water impurities.

light metal sound of the engine that occurs when an increase in traffic may indicate the detonation.So we call a phenomenon in which the fuel burns in the hundreds of times faster than under normal conditions.When you knock a shock wave that during movement of the piston down dozens of times is reflected by the piston and the cylinder head, causing the same knock.In addition to the knock, knock on the decline may indicate the engine power, shaking the unit during operation, the overheating of the cylinder head.The cause of the detonation are the use of low-octane fuel, deposit formation in the combustion chamber, the failure of the EGR valve.The result becomes a detonation damage to pistons and piston rings.