What causes the abnormal sound of the loader diesel engine

[DIG-DOG]

There is a crisp metal knocking sound in the cylinder head cover, and when the diesel engine is changing speed at medium and low speed, the knocking sound is more obvious and clear. There is a regular "da, da" sound, mainly due to the valve gap is too large. The sound of the diesel engine does not change when the temperature of the diesel engine is increased or the test by the method of "cylinder break" is used. When the diesel engine is running at high speed, the knocking sound is not obvious because of the large noise of other machinery. The main reasons for excessive valve clearance are: the valve adjustment screws are loose, so that the screws withdraw or the moving parts of the valve mechanism (such as CAM, tappet, rocker arm, etc.) wear. When the valve clearance is too large, the diesel engine will be underinflated due to insufficient intake or exhaust, resulting in reduced power and increased fuel consumption, and the valve clearance should be adjusted in time.

2, piston pin ring
The main reason for the piston pin ring is that the piston pin, connecting rod bushing or piston pin seat hole wear, resulting in excessive clearance, piston pin impact in the movement and sound. The characteristics of piston pin sound are: from idle to medium speed running, the sound is more obvious; The period (frequency) of the sound varies with the rise and fall of the engine speed. When the injection time is advanced, the sound is more obvious and clear. After the engine temperature rises, the sound generally does not weaken, and sometimes it is significantly strengthened. The sound was reduced or disappeared by the test of broken cylinder.

3. The piston knocks the cylinder
The common and main reason for the piston knocking sound is that the piston and the cylinder wall wear, the clearance exceeds a certain limit, the piston swings in the process of up and down movement, striking the cylinder wall and making a sound when and when. Sometimes, although the fit clearance does not exceed the limit, if the connecting rod is bent and deformed, it will sound. When the temperature of the diesel engine is low, the sound is obvious, and it is particularly clear when idling. The sound decreases or disappears as the temperature rises. This is the characteristic of the piston knocking. Due to the similarities between the cylinder knocking sound and the piston pin sound, in order to facilitate the difference, a little oil can be injected into the top of the piston from the injector seat hole, and after several turns of the crankshaft, the diesel engine can be started again. If the sound disappears immediately after starting, it is the sound of knocking the cylinder. It should be noted that when the oil is supplied in advance (within the specified range), it will also cause a slight knocking sound, which is a normal phenomenon.

4, connecting rod bearing ring
The main reason for the bearing noise of the connecting rod is that the journal and bearing wear, the bearing alloy layer is burned out, off, the bearing cover (tile cover) is loose, the bearing rotates (the bearing shell goes round), and the instant of work hits each other and rings. The characteristics of connecting rod bearing noise are: the sound is obvious at medium speed, it is not obvious at high speed due to the increase of other mechanical noise, and the sound is weakened at idle speed. When the temperature of diesel engine changes, the sound does not change. In the medium speed range, when increasing and decelerating, the sound will become larger with the increase of the speed. Cylinder break test, the sound becomes smaller or disappears.

5. Crankshaft bearing ring
The reason of crankshaft bearing ring is the same as the connecting rod bearing ring, which is characterized by: the sound is dull compared with the knocking cylinder, the piston pin and the connecting rod bearing. When refueling or suddenly slowing down, the sound is obvious and clear; If the bearing alloy layer burns out and falls off, the diesel engine will jitter. Heavy operation, the sound is obvious and clear. The sound does not change when the engine temperature changes. When the bearing ring occurs, the single cylinder "broken cylinder" test shows no obvious change in the sound. Two adjacent cylinders "break cylinder" test, the sound will become smaller or disappear. In addition, you can also use a metal rod or a wooden handle screwdriver to touch the diesel engine external body at the bearing.
Note: If the noise is caused by too much clearance between the bearing and the bearing neck, the oil pressure will decrease significantly.

6, camshaft bearing ring
The common and main cause of camshaft bearing noise is the wear of camshaft and bearing (bushing), and the matching clearance is too large; The bearing alloy layer is burnt out, fallen off, or the outer diameter of the bearing and the seat hole bearing "go round". Camshaft bearing noise is a intermittent rhythm of blunt heavy "tap, tap" at medium speed, the sound is obvious, and can also be heard at idle speed. Engine temperature changes or cylinder break test, the sound does not change.

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