When choosing used hydraulic parts for excavators, there are three core points: first, check whether the model and displacement of the pump/motor/valve match the original machine; second, confirm the condition and inspection report; finally, when comparing prices, factor in after-sales service and logistics. Taking a 20-ton excavator as an example, the price of an OEM remanufactured hydraulic pump assembly is usually 18,000–35,000 RMB, a used dismantled part is 8,000–16,000 RMB, and a used multi-way valve is about 3,000–9,000 RMB. Parts priced far below this range are likely to have hidden damage or be refurbished. Before buying, ask the seller to provide a pressure test video and photos of internal wear—this is much more reliable than just looking at the appearance.
Why Hydraulic Parts Selection Often Goes Wrong
The excavator hydraulic system is a high-pressure precision system, with working pressures generally at 30–35 MPa. If the matching among the pump, valve, and cylinder is slightly off, the symptoms are slow operation, engine stall, and high oil temperature. Many owners only care about “it works” when replacing parts, but end up with incorrect displacement or mismatched pilot pressure, and have to remove the part again after two days of work. The used parts market is even more complex: pumps of the same model may have different control methods (negative flow, positive flow, load sensing), and although they look similar, performance can be significantly worse once installed. The first step in selection is not bargaining, but accurately copying the model and serial number from the original machine's nameplate, and then checking the parts catalog to confirm the variant code.
Key Selection Points for the Three Major Components
- Hydraulic pump: Confirm displacement (e.g., K3V112, A8VO107), control method, rotation direction, and mounting flange. For used pumps, require the seller to provide no-load and load pressure curves; idle pressure should be stable at 3–4 MPa, and relief pressure should reach the standard value without dropping.
- Hydraulic motor: For travel motors, focus on wear of the reduction gear and seals of the brake valve; for swing motors, check the valve plate and plunger pair. The price of a used travel motor assembly is about 6,000–15,000 RMB, and a swing motor is about 4,000–10,000 RMB.
- Multi-way valve: Verify the number of sections, port sizes, and pilot control type. Worn spools can cause engine stall during combined operations. When purchasing, require testing of each section's operation; the pressure difference for a single section's directional change should not exceed 1 MPa.
If the original machine is to be exported to Southeast Asia, Africa, or South America, it is recommended to give priority to OEM parts or remanufactured parts with inspection reports. In high-temperature and high-humidity environments, aftermarket seals often cannot last through one work season.
Common Faults and Troubleshooting Approaches
When hydraulic parts have problems, don't rush to replace the entire assembly. If operation is slow and weak, first measure the main pump pressure, then check whether the pilot pressure is 3.5–4 MPa; if oil temperature is high and speed drops, check the radiator and return filter—many cases of “pump failure” are actually clogged filters. Abnormal pump noise accompanied by pressure fluctuation is mostly due to air intake in the suction line or wear of the plunger pair. Common faults of multi-way valves are spool sticking and internal leakage, manifested as slow single action or no return flow in neutral. During disassembly and inspection, check the degree of scoring on the valve body; minor scoring can be repaired by grinding, and only severe scoring requires replacing the valve body. For motor oil leakage, first check the skeleton oil seal and the back pressure of the drain line; back pressure exceeding 0.3 MPa will push out the oil seal.
Practical Maintenance and Life Extension Tips
- Test hydraulic oil particle count every 2,000 hours; change the oil when the NAS level exceeds 9—don't wait until it turns black.
- Replace return and suction filters every 500 hours; in dusty mining conditions, shorten to 300 hours.
- After each part replacement, first flush the system at low pressure, then perform pressure adjustment according to standards to prevent welding slag and debris from entering the valve.
- For equipment stored long-term, start and run it for 10 minutes every week to keep an oil film inside the pump and motor.
Colleagues engaged in used construction machinery export should note that before shipping hydraulic parts, the oil must be drained and all ports plugged, and a moisture-proof bag should be added inside the wooden crate. For shipments to the Middle East and Africa, it is recommended to include an English inspection report and pressure test data in the crate, which makes customs clearance and customer acceptance easier.
Frequently Asked Questions (FAQ)
How can I tell if a used excavator hydraulic pump is good or bad?
Check three points: whether idle pressure is stable, whether pressure reaches the standard value under load, and whether there is obvious scoring on the plungers and valve plate inside the pump. The most direct way is to ask the seller for a pressure test video with the machine at operating temperature.
Should I choose OEM or aftermarket hydraulic parts?
For projects with tight schedules and for export equipment, OEM or OEM remanufactured parts are recommended; for temporary emergencies and older machine models, aftermarket parts of stable quality can be considered, but seals and plunger pairs should not be skimped on—the price difference often lies in these areas.
What is the approximate price of a used multi-way valve?
For a 20-ton excavator, the common price of a used multi-way valve is 3,000–9,000 RMB; those with more sections and pilot locks are more expensive. Valves below 2,000 RMB mostly have severely worn spools and are not recommended.
Why is the operation still slow after replacing the hydraulic pump?
First check the pilot pressure and relief valve, then confirm whether the pump's control method matches the original machine. Incorrect displacement or installing a positive-flow pump in a negative-flow system will both cause slow operation and engine stall.
What documents are required for exporting used hydraulic parts?
Normally, a commercial invoice, packing list, certificate of origin, and inspection report are required; some countries require a fumigation certificate. Plugging oil ports and draining oil are basic requirements. It is recommended to include English operating instructions with the shipment.
How is after-sales service for hydraulic parts generally guaranteed?
Reputable sellers usually provide a 30–90 day warranty for used pumps and valves, and up to 6 months for remanufactured parts. Before ordering, write the warranty scope into the contract and clarify whether labor and freight are included to avoid disputes.
Post Comment 0