Water Outlet Pipe / Thermostat Cover 8-94390520-1 / 8943905201 For ISUZU NPR 4HK1 6HK1 Hitachi ZX200-3 ZX330 — Aluminum Die-Cast, 0.8 Kg, OEM-Spec

The Water Outlet Pipe / Thermostat Cover with OEM references 8-94390520-1 / 8943905201 is a verified replacement cooling-system component for ISUZU 4HK1 and 6HK1 diesel engines, used across ISUZU NPR light trucks and a wide range of Hitachi, , and JCB construction equipment platforms. This component is the thermostat housing cover / water outlet that seats the thermostat, seals the coolant cavity, and provides the outlet passage directing coolant from the engine toward the radiator.

The unit is manufactured from aluminum die-cast (aluminum pressure casting), providing excellent heat dissipation, corrosion resistance, and resistance to thermal deformation under sustained heavy-duty operation. It is supplied as a brand-new OEM-specification aftermarket component with a reference net weight of 0.8 kg. The HS code is 840999100, and the pack quantity is 1 PCS.

This outlet pipe / thermostat cover is confirmed for ISUZU 4HK1 and 6HK1 diesel engines. It is not a universal ISUZU cooling component — other engine families (4JB1, 4HG2, 4BD1) use different thermostat housing and outlet configurations. Confirm the engine code before ordering.

Across different supplier catalogs, this component is described as "Water Outlet Pipe" (PIPE; WATER OUTLET / ROHR; WASSERAUSLAUF), "Thermostat Cover", and "Thermostat Seat". These terms converge on the same functional component — the housing/cover that holds the thermostat and provides the coolant outlet passage. Confirm the physical form against the original unit.

The cover is confirmed for Hitachi ZX200-3, ZX210K-3, ZX210-3, ZX225US-3, ZX240-3, ZX250-3, ZX270-3, ZX330, ZX330-3 and a broad range of additional Hitachi, (245GLC, 225DLC, 230GW, 220DW, 190GW), and JCB equipment. Provide the equipment model and serial number for final confirmation in mixed-fleet applications.

• VerifiedOE Reference Group: 8-94390520-1, 8943905201, 8-94390-520-1, 8-94390-5201, 894390-5201, 8943905201 are consistently grouped as interchangeable references. Related references 8-94390520-0, 8-94390-520-0, 894390-5200, 8943905200 are also documented.
• VerifiedEngine & Equipment Coverage: ISUZU 4HK1, 6HK1 — confirmed by multiple supplier catalogs. ISUZU NPR — confirmed by DEAUTO application data. Hitachi ZX200-3, ZX210K-3, ZX330 — confirmed by FridayParts and HUPARTS fitment lists. 245GLC, 225DLC, 230GW, 220DW, 190GW — confirmed by HUPARTS application data.
• VerifiedNet Weight: 0.8 kg — confirmed by German-language supplier data. Note: One Russian-language source lists 1.000 kg for the same reference — this may reflect packaging weight or a measurement convention difference. Confirm net weight at inquiry if precise freight planning is required.
• VerifiedHS Code: 840999100 — confirmed by German-language supplier data.
• VerifiedWarranty Reference: 1 year (FridayParts reference) / 2 years (HUPARTS reference) — confirm tier at inquiry.
• VerifiedMOQ & Supply Reference: MOQ 1 pc; supply capacity 1,000 pcs/month; delivery 1–8 working days — confirmed by German-language supplier data.
• AttentionPrecise Thermostat Cavity / Port Diameter NOT Publicly Published: The accessible supplier data does not publish the thermostat cavity bore diameter or coolant port bore for 8-94390520-1. Measure the original unit or confirm against the thermostat part number before ordering if precision matching is required.

• Coolant leak at the thermostat housing / outlet pipe joint: Visible drips, dampness, or crusty residue (white/pink coolant crust) around the housing-to-cylinder-head interface or the outlet-to-hose connection — the most direct sign of a failed gasket, warped sealing surface, or cracked housing.
• Overheating or temperature fluctuation: A housing that does not seal correctly allows coolant loss or air ingress, disrupting thermostat operation and causing temperature instability, especially under load.
• Coolant residue on the engine block or under the machine: Dried coolant around the thermostat area indicates a slow weep that should be addressed before it becomes a sudden failure.
• Cracked or deformed aluminum housing: Impact damage or over-torqueing of the mounting bolts can crack the die-cast aluminum housing, requiring replacement.
• Thermostat not seating properly: A distorted housing cavity can prevent the thermostat from sealing, causing continuous coolant bypass and extended warm-up times.
• Visible corrosion or pitting on the aluminum sealing surface: The aluminum cover can corrode at the coolant passage edges, preventing the gasket from sealing even when new.

• Engine code is the first check: This outlet pipe / thermostat cover is confirmed for 4HK1 and 6HK1 engines. Confirm the engine code against the vehicle or equipment documentation before ordering.
• Cover / housing only — thermostat is separate: This listing covers the housing/cover only. The thermostat element (82°C or 85°C rated) is not included and must be ordered separately if a complete repair is required.
• Equipment coverage breadth: The same component serves ISUZU NPR, Hitachi ZX-series, , and JCB applications. Provide the equipment model and serial number for final confirmation in mixed-fleet applications.
• Related reference 8-94390520-0: The -0 suffix reference is grouped with the -1 as interchangeable. Confirm the original unit's marking where possible.

1. Confirm the required part first: Verify the engine code (4HK1 / 6HK1) and equipment model (NPR / ZX200-3 / ZX330). Confirm whether the replacement is a cover/pipe and that the cavity and mounting points match the original unit.
2. Cold engine only: Allow the engine to cool fully before opening the cooling system. Drain coolant to a level below the thermostat cover.
3. Remove the old cover: Disconnect the coolant hose if attached. Unbolt the cover from the thermostat housing. Note the orientation of the thermostat and any gaskets or seals.
4. Clean the mating surface: Remove all old gasket residue and corrosion from the housing face and the cover sealing surface. A clean, flat surface is essential for a leak-free seal.
5. Inspect the thermostat: Check the thermostat for correct operation. Replace if stuck open or closed. Confirm the correct temperature rating (82°C or 85°C).
6. Install the new cover with a new gasket: Seat a new gasket, position the 8-94390520-1 cover, and insert the mounting bolts. Do not over-torque — the aluminum die-cast housing can crack or distort.
7. Reconnect the hose and refill coolant: Reconnect the coolant hose if applicable. Refill with the correct coolant mixture and bleed the system according to the equipment or vehicle procedure.
8. Run and verify: Start the engine, bring it to operating temperature, and check for leaks at the cover joint. Confirm the temperature gauge stabilizes.

• Inspect the cover joint at every coolant service or every 500 hours (equipment) / 20,000–30,000 km (vehicle) — look for crusty residue or dampness.
• Replace gaskets whenever the cover is removed — gaskets are single-use compression seals.
• Flush coolant according to the manufacturer interval. Degraded coolant accelerates aluminum corrosion.
• Replace the cover if the sealing surface is pitted, the cavity is distorted, or a crack is detected in the die-cast housing.

• Standard packing: Neutral package or customer-specified packaging — confirmed by supplier terms. Bulk export carton available.
• Package contents: 1 × Water Outlet Pipe / Thermostat Cover. Thermostat element is NOT included unless explicitly stated — confirm at inquiry.
• Set options: Cover/pipe only (standard) / cover + thermostat + gasket kit (where available) — specify at inquiry.
• Suitable for: ISUZU NPR cooling-system repair shops, Hitachi ZX-series / JCB equipment service providers, construction machinery maintenance departments, spare parts distributors, and export wholesalers.