1. When the diesel engine has a heavy and continuous knocking sound at the lower part of its crankcase, the sound is clear and identifiable at low speed, and it is more obvious at heavy load. .

2. When the starter of the flat-mouth self-feeding mixer truck suddenly changes the speed at low speed, there will be a sound of "clang, clang" in the upper part of the cylinder, which is caused by the excessive clearance between the piston pin and the connecting rod bushing, or with the piston pin seat. To.

3. When the flat-mouth self-feeding mixer starts running at high speed, it makes a muffled sound of "click, click", which is especially serious when the throttle is suddenly reduced, which is caused by the excessive axial clearance of the main bearing bush

4. When you hear a roaring and dull "empty dong, empty dong" knocking sound at the full length of the cylinder, and when you open the oil filler cap, you find air bubbles (indicating that there is air leakage), which is the piston and the cylinder. Due to the excessive clearance of the sleeve.

5. If you hear the impact sound of "quack, quack, quack" at the same part slightly in the direction of the crankshaft, it is the percussion sound caused by the twisting of the connecting rod causing it to shake during work. The latter two sounds are more obvious when the speed is changed. You can hear it, and it is easy to distinguish; there is a similar sound of a small hammer hitting the iron block along the upper and lower parts of the cylinder, and blue smoke from the diesel engine exhaust pipe (accompanied by the phenomenon of burning oil), use a long-handled screwdriver to touch the cylinder If it is easier to hear at the body, it can be determined that the piston ring side clearance is too large or the ring is broken.

6. When the diesel engine suddenly changes the load, a rapid "empty, empty, empty" dull percussion sound can be clearly heard near the crankcase (from the middle to the lower part of the cylinder block), and with the increase of load or speed And the sharp change, the sound increases, open the oil filler cap can be heard more clearly, it is not obvious when there is no load. This is due to the excessive wear of the connecting rod bush, resulting in an excessive clearance between the connecting rod bush and the crankshaft connecting rod journal.

7. If the oil in a certain cylinder of the diesel engine is cut off, if the abnormal sound disappears immediately, it means that the connecting rod of the cylinder is sounding.