Diesel engines generally produce the following abnormal sounds:
1. Piston and cylinder liner knocking sound, the sound is mute knocking sound;
Reason: When the injection pump supplies oil too early or the cylinder liner and piston wear clearance is too large, the piston top dead center knocks the swing head and cylinder liner under the action of gas expansion.
Judgment method: Cut off the oil supply of each cylinder and listen carefully. If the sound disappears, verify the cylinder position.
2. The knocking sound of the main bearing and the main journal;
Reason: When the main bearing is severely worn or burned, a heavy muffled knocking sound will occur.
Judgment method: Check the abnormal sound source by medium speed or intermittently increasing the speed.
3. The knocking sound of the connecting rod copper sleeve and the piston pin.
Reason: When the connecting rod bushing is severely worn or poorly lubricated, it will sinter with the piston pin, and produce abnormal sound, which is accompanied by a crisp "dangdang" sound.
Judgment method: Listen along the piston movement part, and cut off the oil supply. The sound disappears.
4. Knocking sound between valve and rocker arm head
Reason: When the rocker arm is worn, the screw is loose, and the valve clearance is large, a "de-da, da" sound will occur, and the sound is continuous.
Judgment method: At low speed, there is still knocking sound when the oil supply to each cylinder is cut off.
5. Loose valve seat
Reason: The valve seat is loose, causing a "cha, cha" sound, accompanied by bursts of air flow sound.
Judgment method: Continuously throttle several times, move quickly from high speed to low speed, so that the diesel engine is almost shut down, the sound is very obvious.
6. Knocking sound between connecting rod bearing and connecting rod journal
Reason: The connecting rod bearing is severely worn or burned, making the matching clearance between each other too large, and the sound is similar to a dumb bell.
Judgment method: Listen at low speed, listen at low speed, cut off the oil supply to each cylinder, and there is still knocking sound.
