CASE 240 excavator percussion and noise failure summary table:
The valve clearance is too large, the oil advance angle is not adjusted properly, the advance angle is too large, and the oil supply time is too early.
The oil nozzle is not working properly: bitten, dripping oil, and bad atomization produce knocking valve spring break, valve push rod bend, valve tappet wear so that valve mechanism sends out slight percussion sound
The bottom of the piston collided with the bottom of the cylinder liner, and the sound was heavy and strong, and the piston collided with the valve, causing a uniform rhythm of percussion.
The clearance between piston and cylinder liner is too large, and the knocking noise reduces the axial clearance of crankshaft too much as the machine temperature rises.
The gap between the connecting rod bushing and the piston pin is too large and makes a slight sharp sound. The idling speed is more obvious, the air leakage of the intake and exhaust doors, the cylinder cover gasket break, and the unsealed gasket of the injector copper gasket produce rapid air sound.
The foreign body fell into the cylinder and suddenly produced a heavy "Dangdang" metal impact sound.
CASE 240 excavator percussion and noise failure classification:
1 there is a "loud" sound in the hood of the cylinder head. When the exhaust is serious, there are uneven "explosions" and black and white smoke.
2 according to this phenomenon, it can be analyzed that the valve clearance is too large, resulting in bad intake and exhaust and abnormal noise.
3 excessive valve clearance is mainly caused by improper adjustment or other abnormal conditions.
4 the reasons why the valve gap is wrong are: valve push rod bending, wear, tappet round surface sag, adjusting screw loosening, camshaft valve cam wear and so on to make the distribution mechanism a slight percussion sound.
CASE 240 excavator percussion and noise troubleshooting method: adjusting valve clearance method:
The valve clearance should be adjusted at the TDC. The multi cylinder machine should start from the first cylinder and then adjust the valve clearance of each cylinder according to the working order.
When adjusting, first remove the cylinder cover cover, tighten the valve rocker seat bolt, rotate the flywheel according to the rotation direction of the work. When the 0 line on the belt wheel aligns with the pointer of the gear chamber, it turns the crankshaft back and forth. At the same time, watch the valve rocker arm of the one and four cylinders, if the rocker arm of the inlet valve of one cylinder does not move up and down, it indicates that the cylinder has been compressed up and down. When the flywheel is rotated back and forth, the exhaust gate of the fourth cylinder will be closed and the intake door will stop when the door will open. It also indicates that the first cylinder can adjust the gap between the valve and the valve. After the adjustment, the 180 degrees (half rotation) of the flywheel (or the pulley) are rotated each time in the working order of each cylinder, and the clearance of the inlet and exhaust valves of the cylinder is adjusted in turn. End.
The method of adjusting valve clearance by 2 cylinder machine:
When the belt pulley (flywheel) is transferred to the pointer of the gear chamber cover, then turn the pulley (or flywheel), and observe whether the inlet and exhaust door of the first cylinder has the movement, if no movement, it indicates that the first cylinder has been compressed to the stop point, and the clearance of the valve can be adjusted after 360 degrees (one circle), and the second cylinder will be adjusted to 180 degrees. The valve clearance of the second cylinder can be adjusted.
The adjustment method of valve clearance for 3 cylinder machine:
Remove the cylinder cover and tighten the rocker seat bolt. Rotate the pulley clockwise. When the 0 degree scale on the pulley is aligned with the needle of the gear chamber, the flywheel is rotated around the 0 scale. At the same time, whether the inlet and exhaust doors of the first cylinder are moved up and down, if there is a change, the first cylinder is at the exhaust point, and the valve clearance must be adjusted again after 360 degrees. If the intake and exhaust door does not change, it indicates that the stop point has been compressed. Then the 240o is then rotated to adjust the valve gap of the working order of the next working cylinder (working order of 1-3-2).
