Kyotechs Hitachi Hydraulic Pump Rebuild Kit - Reliable Performance

Common causes of control valve failure include internal wear, seal damage, contamination and valve blockage.

Reasons from the piston group
1. The piston ring gap is too small. If the opening gap, side gap or back gap of the piston ring is too small, the piston ring will be stuck due to heat expansion when the engine is working, and it will be pressed tightly against the cylinder wall, or the piston ring will be broken, which can easily pull out grooves on the cylinder wall.
2. The piston pin is out. Because the piston pin retaining ring is not installed or falls off or breaks, the piston pin will be out during movement, which can easily damage the inner wall of the cylinder and cause the cylinder to blow into the crankcase.
3. The piston cylinder gap is too small or too large. If the piston material is poor, the manufacturing size error is too large, or the piston is deformed after the piston pin is assembled, the matching gap between the piston and the cylinder is too small, and the piston is stuck after heat expansion, which will then damage the cylinder wall.
4. The piston ring is seriously carbonized. Excessive carbon deposits cause the piston ring to stick or bite in the ring groove. At the same time, carbon deposits are a hard abrasive that will grind into longitudinal grooves on the cylinder wall.
5. The piston is seriously off-cylinder. Due to the bending and twisting of the connecting rod, the parallelism and coaxiality deviations of the connecting rod journal, main journal, and piston pin seat are too large, causing the piston to be significantly off-cylinder, which will accelerate the wear of the piston ring, piston and cylinder wall and destroy the formation of the oil film.

Reasons for cylinder sleeves
1. The roundness and cylindricality tolerances of the cylinder sleeves exceed the allowable range, which greatly reduces the sealing of the piston and cylinder sleeves. The high-temperature gas in the cylinder flows down, destroying the oil film between the piston and the cylinder wall, and then causing cylinder pulling.
2. The cylinder sleeve is deformed during the assembly process. For example: the protrusion of the upper end surface of the cylinder sleeve is too large, and the cylinder sleeve is deformed after the cylinder head is installed; the cylinder sleeve water blocking ring is too thick, and the cylinder sleeve is deformed after being pressed into the body, which can easily cause cylinder pulling.

Reasons for use:
1. Whether the size of the cylinder sleeve used during assembly does not match the cylinder body and piston.
2. The air filter is not sealed, which makes the filtering effect worse. Dust, sand and other impurities in the air are sucked into the cylinder, forming abrasive wear. Tests show that if a few grams of dust are sucked in every day, the wear of the cylinder liner will increase by more than 10 times.

1. Chain off caused by tension cylinder failure
At this time, you should check whether you have forgotten to butter the tension cylinder and see if there is any oil leakage in the tension cylinder.

2. Chain off caused by severe wear of the crawler
If used for a long time, the crawler will definitely be worn, and the wear of the chain ribs, chain barrels and other parts on the crawler will also cause the crawler chain off.

3. Chain off caused by wear of the chain guard
Now almost all excavator crawlers have chain guards, and chain guards can play a very important role in preventing chain off, so it is also very important to check whether the chain guard is worn.

4. Chain off caused by wear of the drive motor ring gear
For the drive motor ring gear, if it is severely worn, we need to replace it, which is also an important reason for the excavator chain off.

5. Chain off caused by damage to the sprocket wheel
Generally speaking, oil leakage of the sprocket wheel oil seal of the excavator will cause severe wear of the sprocket wheel, which will cause the crawler chain off. The public account Zhizao Daguan focuses on sharing relevant theoretical knowledge in the engineering machinery manufacturing industry.

6. Chain derailment caused by guide wheel damage
When checking the track guide wheel, check whether the screws on the guide wheel are missing or broken. Check whether the groove of the guide wheel is deformed.

1.There is no oil in the fuel tank.

2.The fuel filter and oil-water separator are blocked.

3.The low-pressure oil circuit does not supply oil.

4.The injection pump does not pump oil.

5.There is air in the oil circuit.

6.The valve timing is misaligned. The opening time of the valve is not coordinated with the stroke of the piston in the cylinder. For example, when the piston makes a compression stroke in the cylinder, the intake and exhaust valves are open, and fresh air is driven out of the cylinder, so that there is no combustion gas in the cylinder and it cannot start.

7.The solenoid valve of the injection pump is broken and is in a closed state, and the diesel cannot enter the high-pressure chamber.