1. Check the filter, clean or replace if it is clogged. Observe the oil, and replace the oil if it deteriorates.
2. Check the pipelines in the hydraulic system. If the pipes and joints are damaged, replace or repair them.
3. Check whether the sealing ring of the hydraulic cylinder piston has lost its sealing effect. The hydraulic cylinders of the working device, that is, the boom, the stick, and the bucket are bottomed one by one, and then the high pressure oil pipe of the outlet joint of the large cylinder of the hydraulic cylinder is removed, and the control phase Corresponding to the control handle of the hydraulic cylinder, the hydraulic cylinder retracts the piston rod further. Since the piston rod has reached the bottom at this time, it can no longer move and the oil pressure is increased, carefully observe whether there is oil outflow at the outlet of the large cavity of the hydraulic cylinder. If there is a small amount of oil flowing out from the outlet, the seal ring of the hydraulic cylinder does not fail; if a large oil flow is formed, the piston seal ring of the hydraulic cylinder fails, and the hydraulic cylinder should be repaired and replaced.
4. Under the conditions of high-speed idling of the engine and unloading of the stick, gradually measure the overflow pressure of the control pump and the front and rear main pumps, and measure the pressure of the torque control valve. Its specified value: the overflow pressure of the control pump is 3 ~ 3.8MPa, The overflow pressure of the front and rear main pumps is 31 ~ 34.5MPa, and the pressure of the torque control valve (TVC valve) is 1.8 ~ 2.0MPa.
When the relief pressure of the control pump, the front and rear main pumps and the set pressure of the TVC valve are within the specified values, and the front and back main pumps are overflowing, the main pump has internal leakage and the main pump should be repaired.
When the measured overflow pressure of the control pump and the front and rear main pumps are within the specified value, and the measured TVC valve set pressure is not within the specified value, adjust the TVC valve set pressure to the specified range, the fault is eliminated. The pressure of the valve cannot be adjusted, the TVC valve is faulty, and the TVC valve should be disassembled and cleaned. If the main spool of the TVC valve is stuck, the valve core hole is ground and repaired so that it can be pushed freely, otherwise the TVC valve is replaced.
5.Control the overflow pressure of the pump within 3 ~ 3.8MPa, and the front and back main pump overflow pressure is not within 31 ~ 34.SMPa, then adjust the overflow pressure of the main overflow valve of the front and back main pump to the specified value, Fault elimination. If the pressure of the main relief valve cannot be adjusted, the main relief valve is faulty, and the main relief valve should be disassembled and cleaned. If the main relief valve is stuck, clean the main spool so that it can be pushed freely. Yes. When the spool cannot be pushed freely, the main spool hole can be ground and repaired, or the main overflow valve can be replaced.
6. The overflow pressure of the control pump is not within 3 ~ 3.8MPa, then adjust its overflow pressure to the specified value, and the fault is eliminated.
When the overflow pressure of the control pump cannot be adjusted, the 1 ~ 6 circuits should be cut off according to Figure 11-59. Measure the overflow pressure of the control pump and its value is within 3 ~ 3.8MPa, then the corresponding control element has serious internal leakage , The corresponding control element should be repaired; if the pressure is not within 3-3.8MPa, check the oil discharged from the outlet filter of the control pump for iron powder and foreign debris. Maintenance or replacement; if not, the main spool of the control pump overflow valve should be cleaned, the main spool hole should be ground or the control pump main overflow valve should be replaced.
7. When it is found that the hydraulic control component of the PPC valve is faulty, the spool and valve body of the main control valve control working device should also be cleaned. At the same time, check the gap between the spool and valve body, the normal value is 0.015-0.025mm, the maximum The gap should not exceed 0.04mm. If the gap is too large, or the valve core is seriously worn, the group of control valves should be replaced; check the spring, if there is deformation, soft or broken, it should be replaced.
