The connecting rod bush of the engine is used to protect the connecting rod journal and the connecting rod big head hole. The connecting rod bearing is made up of the steel back and the wear reducing layer. The steel back is made of low carbon steel with a thickness of 1~3 mm, and the anti wear layer is 0.3 to 0.7 mm thick, which is soft and can protect the axle neck. 1. phenomenon (1) when sudden acceleration, the engine sends out a clear and continuous sound like a wooden stick knocking on the iron barrel, which is more crisp than the spindle; (2) the sound is smaller at idling, and the medium speed is obvious; (3) the sound of a single cylinder is obviously weakened or disappearing after a fire, and (4) the sound of a vehicle at high speed or climbing. Intensifying. 2. reasons (1) the loosening of the bolt cap bolt; (2) the radial clearance of the connecting rod bush is too large; (3) the alloy layer of the connecting rod bush is burned down; (4) the engine oil is bad. 3. diagnosis and elimination (1) when the engine starts to start, the sound is serious and the noise is weakened or disappeared after the pressure of standby oil rises. It indicates that the gap of the bearing bush of the connecting rod is slightly larger or the alloy layer is peeled off. (2) if the engine temperature is normal and the speed is suddenly added from low speed to middle and high speed, the engine makes a rhythmic "when, when" sound; when the speed rises, the sound of the engine is weakened until it is disappearing. When the single cylinder is broken, the noise disappears and the noise is restored when the fire is resumed. The sound of a little joint is more obvious, indicating that the gap between the connecting rod bush is too large and the connecting rod axle neck or replacement of the connecting rod should be repaired. (3) engine temperature increases, noise increases, indicating that engine oil does not meet the requirements, should be replaced. If the engine speed is increased at the same time, the noise will weaken but appear chaotic. It means that the alloy layer of the connecting rod bearing bush is overheated and melted and should be repaired immediately. The crankshaft spindle bush is installed on the fixed bracket of the crankshaft and the cylinder body to play the role of the bearing. The diesel engine crankshaft main bearing clearance is 0.12 ~ 0.207 mm, and the crankshaft main bearing wear limit is not more than 0.17 mm. 1. phenomenon (1) when the engine speed suddenly changes, the heavy and powerful, continuous "mile, pupil" metal knocking sound, serious vibration occurs in the engine when serious; (2) the higher the engine speed, the sound noise is greater; (3) the engine sound increases with the load; (4) the engine single cylinder breaking fire, sound sound not obvious change When the adjacent two cylinders break off, the sound will obviously decrease; (5) the oil pressure will obviously decrease. 2. reasons (1) the looseness of the bolt cap bolt or bolt torque did not reach the specified value; (2) the spindle or shaft neck is too worn, the axial thrust device is too worn, leading to excessive radial clearance and axial clearance; (3) bad lubrication causes the bearing alloy to burn down or fall off; (4) the axle neck disintegration, poor quality of bearing, assembly Improper early damage; (5) oil pressure is too low or oil deterioration; (6) crankshaft bending; (7) flywheel fastening bolts loose. 3. diagnose and remove (1) open the cover of the oil filler port of the oil pan, and change the engine speed again and again. If there is an obvious heavy percussion sound, the spindle bush will ring. (2) the engine works at normal temperature. When the engine speed is accelerated from low speed to medium speed, the sound of hall and hall is rhythmic and blunt. The higher the engine temperature (the lower the oil Bob) is, the more obvious the sound is, the sound of the sound becomes messy at the high speed, and it may be the crankshaft spindle ring caused by the crankshaft bending. (3) if the body has a large vibration at high speed, when the vehicle is climbing the slope, there is a sense of vibration in the cab, and the oil pressure drops significantly. It shows that the gap between the main shaft tiles is too large and the alloy falls off, so it should be repaired in time. (4) if the sound occurs in the rear of the engine, and a sound of impact occurs at the moment of sudden rise or reduction of the engine speed, the loosening of the fastening bolt of the flywheel should be tightened according to the specified torque. Piston knocking will cause fuel consumption and engine oil consumption to increase. When the piston knocks badly, it will also break the piston, knock the cylinder, even break the connecting rod, and destroy the cylinder block. 1. the knocking noise varies with the temperature of the diesel engine. The sound is more pronounced at low temperature, and the noise decreases or disappears when the temperature rises. When the speed is suddenly raised, the continuous metal percussion sound will be issued. If the multi cylinder piston knocks, when the speed rises, the noise is noisy and disorder. 2. reasons (1) the gap between the piston and the cylinder wall is too large; (2) the quality of the cylinder sleeve, piston and piston ring is poor, and the lubrication is bad. After a period of running, the cylinder, piston and piston ring wear seriously, so that the cylinder plug fits the gap too much, causing the piston to knock in the cylinder when the engine works; (3) the piston is heated and deformed, and (3) the piston is heated and deformed, and the piston is heated and deformed The roundness and cylindricity errors formed by irregular wear are more than stipulated; (4) the bending or distortion of the connecting rod makes the piston skew in the cylinder and makes the piston knock; (5) the connecting rod bearing and the connecting rod shaft neck or the piston pin are tight with the connecting rod bushing. 3. diagnose and remove (1) open the cover of the oil filler port. When you hear the knocking, you can also see that there is a blue smoke coming out of the oil inlet. If you use the screw to reach the top of the cylinder, if you can hear the percussion sound like a small hammer knocking on the cement floor, it means piston knocking. (2) break the cylinder one by one, if it is broken to a certain cylinder, the sound is obviously reduced or disappeared, and when the oil supply is restored, the sound can be heard. It shows that the cylinder has a piston knocking and should be repaired in time. (3) when the cylinder head is dismantled and the piston is checked, the corresponding treatment or replacement repair should be carried out if the cylinder has been found to be severely round, pulled, connected with the connecting rod, the piston pin and the connecting rod bushing are too tight, the connecting rod bearing and the connecting rod neck are too small and the piston top is too much carbon.