Our masters who drive small excavators know that after a long time, excavators will have some stubborn problems more or less, such as small excavators with abnormal noise faults, which is a "stubborn disease" that many old drivers are unwilling to face, because if there is no rich Based on experience, it is difficult to accurately determine the source of the abnormal noise, let alone accurately troubleshoot the fault point. In addition, the abnormal sound sounds different and the location is different, and the possible fault points are very different, so it is a waste of time for everyone to deal with it. The construction period was delayed again. Today, the engineer will share with you the troubleshooting process of the abnormal sound when the car is cold.
Symptoms:
According to the boss in Sichuan, the machine has been running by itself, and usually there is a disturbance that can be observed immediately. In the past two days, it has been found that the machine will make an abnormal sound of "just now" when it is cold.
The machine only has more than 7,000 hours, and it is usually maintained carefully, and there have been no major problems, so the owner of the machine was not too nervous at the first time. In addition, there was only abnormal noise when the machine was cold, and the machine worked for a while. After time, the temperature gradually weakened or disappeared directly. To be on the safe side, the owner of the machine turned to the maintenance master for help.
Fault analysis:
According to usual experience, after observing the faulty machine on the spot, the maintenance master said that the fault point is most likely caused by the excessive fit gap between the piston and the cylinder liner. One of the common causes of fading away.
Following this analysis thread, let's take a look at the whole process of overhaul.
Troubleshooting process:
Step 1: After the master arrived at the scene, he reproduced the fault first. After careful observation and testing, the fault was confirmed to be consistent with the owner's description. At the same time, the maintenance master found that the working power of the engine dropped slightly, and the speed dropped when the load was applied, and the car was held back.
Step 2: Through principle analysis, when the engine is in a cold state, there is an adaptive gap between the piston and the cylinder liner. When the gap is too large during operation, the piston moves within the range of the gap and hits the wall of the cylinder liner to make an abnormal knocking sound.
Step 3: In-depth observation of the working time of the excavator gradually prolongs. After the oil temperature rises, the piston with a large thermal expansion index (caused by the material) gradually increases as a whole, which narrows the matching gap with the cylinder liner, so the abnormal noise is random and warm. Decreased or disappeared.
Step 4: The maintenance master used an infrared thermometer and found that the temperature of one of the cylinders was lower than that of the other cylinders. For the sake of accuracy, the master used the cylinder pressure gauge to test the cylinder pressure. The cylinder pressure of this cylinder is very low, basically the fault point is locked up.
Step 5: After careful inspection, it was found that the fit gap between the cylinder liner and the piston exceeded 0.35-0.40. After replacing the new parts, the sound just now disappeared obviously, and the fault problem was solved here.
Many times, before a small excavator breaks down, there will be minor or severe failure phenomena and abnormal sounds. These are the distress signals sent by the machine to everyone! So old drivers must not take it lightly.