What is that knocking?
An engine knock never means anything good and unfortunately is a signal that we are going to spend a lot of money in the near future.
In order to have as few of them as possible, it is necessary to make the correct diagnosis.
The engine is a very complex mechanism and there are many malfunctions in it. One of the signs of damage is a knock that doesn't match the normal engine noise. When starting a cold engine, the noise level is much higher than when the unit is on. 
warmed up to operating temperature. This is the case with diesel engines, which are characterized by a low culture of work after start-up. This is normal and you shouldn't worry about it. However, when after a few or a few seconds, or until the engine has warmed up, a metallic knock is heard near the valve cover, this indicates damage to the hydraulic lifters. The reason for this can also be the wrong oil or oil that has not been changed for a long time. Such a knock can be heard even in the absence of hydraulic adjustment. Then you need to adjust the valve clearances. This event costs between PLN 30 and 500, depending on the complications.
Unfortunately, it may turn out that the cause of valve cover knocking is a damaged camshaft, or rather the cams that open the valves. A new roller is expensive, so you can try to restore it (30 to 50 PLN per cam) or buy a used one.
Metallic knocking can also occur when the engine is warm. If they occur under load and low engine speeds, then this is knocking combustion that occurs in a gasoline engine running on low-quality fuel or when the ignition timing is incorrectly set. Also under load, whether the engine is hot or not, the bushings and the piston pin make themselves felt. The sound will be muffled and muffled and clearer under load, but will disappear completely when you let your foot off the gas pedal. The pin will be heard above and the projectiles below the engine. 
Diagnosis is very difficult due to the high noise emitted by the engine. A stethoscope will help you a lot, thanks to which you can accurately listen to the engine.
The timing drive can also be noisy. A worn chain will cause a characteristic rustle. Do not change the chain immediately, as noisy operation can be caused by a damaged tensioner or too low oil pressure, which will have a decisive effect on the degree of chain tension.
Various noises can also come from accessories, tensioner bearings or loose V-belts. But these sounds are very characteristic, so a good mechanic should have no difficulty in correctly diagnosing.
