1
Fit clearance is too large
Fit clearance is an important indicator of automobile assembly quality when lubrication, temperature, the load and speed are constant and abnormal. the noise will increase with adjustment clearance. This becomes more and more evident as the engine increases. Due to natural wear, the clearance of some moving engine parts increases beyond the range, resulting in abnormal noise, such as engine noise. the knocking noise of the piston and cylinder wall, the impact noise of the connecting rod bearing and journal, etc.
2
Poor lubrication
Lubrication is an important condition for normal engine operation. Lubrication, cooling, cleaning, sealing and rust prevention can be achieved. through the lubrication system. When the game is suitable, when the temperature, load and speedare constant, the thickness of the lubricating oil film is affected by the pressure of the lubrication system and the quality of good quality lubricating oil. and appropriate pressure can produce better lubricating oil film. The thicker the lubricating oil film, the lower the mechanical impact, less prone to abnormal noise. If the lubricating oil film is too thin, resulting in increased wear, abnormal noise will occur, which will be obvious and clear.
3
Loose fasteners
Vibrations are generated during engine operation, causing some parts to become loose and causing impact noises. If the flywheel mounting bolts are loose, the connecting rod bolts are loose, etc., causing abnormal noise.
4
Individual parts are deformed and damaged
Abnormal noise is caused by deformation or damage of a certain part. For example, the flowerxion of the connecting rod causes the cylinder to knock, and the abnormal noise caused by the valve spring breaking and the crankshaft breaking.
5
Abnormal combustion
The ignition time of the gasoline engine is too early or too hot, resulting in deflagration, and the injection time of the diesel engine is too early, resulting in premature roughness and metal damage. The sound of blows on the cylinder.
6
Incorrect adjustment or repair of the assembly
Incorrect adjustment or repair of the assembly results in misalignment of the mounting clearance of the machine parts. Abnormal noise may occur if the piston pin is too tight or the valve clearance is incorrectly adjusted.
7
Speed
Generally, the higher the speed, the louder the abnormal mechanical sound. However, at high speeds, various sounds are mixed. , and some abnormal sounds are mixed. The noise is difficult to hearsting, so the speed diagnosis depends on the abnormal sound situation. For example, when auscultating valve noise and piston knocking noise, the abnormal noise is very obvious at idle. or at low speed. When the main bearing noise, connecting rod bearing noise and piston pin noise In severe cases, it can also be heard at idle and low revs. In short, the diagnosis of abnormal noise must be carried out at the rotation speed. the most obvious noise and should be carried out at low speed as much as possible to reduce noise and unnecessary losses.
8
Temperature
Some abnormal noises are related to engine temperature, while some abnormal noises have little or nothing to do with temperature of the motor. diagnosis of abnormal mechanical noise For fittings with a high coefficient of thermal expansion, particular attention should be paid to the conditions ofoperation of the engine when hot, such as knocking of the piston on the cylinder. When the engine starts cold, the abnormal noise. is very obvious. Once the temperature increases, the sound will weaken or disappear, so diagnose cold cylinder knock. The response is carried out at low motor temperatures and temperature has little effect on abnormal noises produced between mating pairs with low thermal expansion coefficients. Abnormal noises such as crankshaft main bearing noise, connecting rod bearing noise and valve noise have no special requirements for diagnosing temperature. Temperature is also one of the main factors affecting noise combustion. When a gasoline engine overheats, it often produces ignition knock.