Nachi PVD-00B-14P-5G3 4438711 hidraulikus szivattyú Hitachi ZX20U ZX20UR EX20U-3 EX20UR-3 minikotró-hoz

1. Product Identification
Component: Main Hydraulic Variable Displacement Axial Piston Pump Assembly

Manufacturer Model Number: Nachi PVD-00B-14P-5G3 (PVD Series Architecture)

Hitachi OEM Part Number: 4438711

Machine Compatibility:

Hitachi ZX20U / ZX20UR

Hitachi EX20U-3 / EX20UR-3 Mini Excavator

Condition: Genuine Original New / Premium OEM Specification Equivalent

2. Technical Specifications
Pump Type: Variable Displacement Axial Piston Pump with Auxiliary Gear Pump Section

System Performance: Factory-calibrated flow profile, displacement, and operating pressure limits engineered specifically for Hitachi 2.0-ton class mini excavator hydraulic circuits.

Integrated Control Network: Equipped with factory regulators to manage dual piston pump flow and auxiliary gear flow for balanced, smooth multi-function operation.

Drive Configuration: Heavy-duty input spline shaft designed to couple directly with the engine flywheel dampener drive.

3. Critical Installation Requirements
Hydraulic Pump Housing Priming (Mandatory)
Before starting the engine, manually pre-fill the main pump casing with clean, fresh hydraulic fluid through its highest case drain port. Operating an axial piston pump bone-dry—even for a few seconds—will score the valve plate and piston slippers, causing immediate total pressure loss.

Air Bleeding & Initial Startup Procedure
After installation, loosen the air bleed port on top of the pump housing. Crank the engine with the fuel supply disabled until clear, bubble-free oil flows from the port, then retighten. Allow the machine to idle under no load for 10 to 15 minutes to clear trapped air from the main hydraulic loop.

Fluid & System Decontamination
If replacing a pump that suffered internal mechanical failure, completely drain and clean the hydraulic oil reservoir, flush circuit lines, and clean the oil cooler. Replace all return and suction filter elements before starting the engine.

Relief Pressure Check
Verify system pressure relief valve settings upon startup. Incorrect pressure relief settings can lead to sluggish hydraulic controls, circuit overheating, or engine stalling under heavy digging load.

4. Frequently Asked Questions (FAQ)
Q: Is the Nachi PVD-00B-14P-5G3 a direct replacement for Hitachi part number 4438711?
A: Yes. Nachi is the original hydraulic pump manufacturer for these Hitachi mini excavator series. Part number 4438711 cross-references directly to this Nachi PVD-00B model, matching all original physical mounting dimensions, input shaft splines, and port locations.

Q: My Hitachi EX20U-3 bogs down or stalls the engine when performing multi-function movements. Is the main pump failing?
A: Engine stalling under load typically indicates that internal pump wear plates have scored or that the pump load-sensing regulators are failing to destroke properly under load. Replacing the main pump assembly restores proper engine-to-hydraulic power balance.

Q: Does this unit arrive complete with the rear gear pump section attached?
A: Yes. The unit comes fully assembled as a single integrated pump assembly, including the main axial piston pump section, factory-adjusted regulator blocks, and the auxiliary gear pump section.

5. Shipping & Logistics
Packaging: Preserved with rust-inhibiting storage oil, fitted with heavy-duty port plugs, and packed inside an export-safe protective crate or box.

Transit Time: Global express air freight via DHL/FedEx/UPS typically delivers within 3 to 7 business days directly to your workshop or job site.