Thermostat Cover 5137130350 / 5-13713035-0 For ISUZU 4BD1 NFW220 EX100 EX120 — Aluminum & Plastic, 0.25 Kg, OEM-Spec

The Thermostat Cover with OEM references 5137130350 / 5-13713035-0 (and factory reference 5-13713035-YH) is a verified replacement cooling-system component for the ISUZU 4BD1 diesel engine. It has confirmed primary application on the ISUZU NFW220 excavator and broad compatibility across Hitachi EX100, EX120, EX150 and related construction equipment platforms. This is the thermostat housing cover / thermostat cap — the upper enclosure that seats the thermostat, seals the coolant cavity, and controls the coolant flow path to the radiator based on engine temperature.

The unit is manufactured from aluminum and plastic. The aluminum cover provides heat dissipation and resistance to deformation, while the plastic housing interfaces with the coolant circulation channel. This construction is specifically engineered to prevent coolant leakage and resist thermal deformation under sustained heavy-duty operation. The reference net weight is 0.25 kg, with actual dimensions of 21 × 18 × 0.2 cm.

1. ISUZU 4BD1 Engine Application: The primary confirmed engine model is ISUZU 4BD1. Related engine coverage includes 4BC2, 4JG1, and 4BA1 via cross-reference data. Confirm the engine code before ordering — other ISUZU engine families use different thermostat cover configurations.
2. Cover / Cap Scope — Thermostat Element Not Included: This listing covers the thermostat cover / cap. The thermostat element itself is not included and must be ordered separately if a complete repair is required. The cover's function is to house and support the thermostat, not to regulate temperature on its own.
3. Equipment Coverage — NFW220 and EX-Series: The cover is confirmed for the ISUZU NFW220 excavator. Cross-reference equipment data also covers Hitachi EX100, EX100-2, EX100-3, EX120, EX120-2, EX150, EX150-2, SH100, SH120, SK045, SK120-2 and related models. Provide the equipment model and serial number for final confirmation in mixed-fleet applications.

• ✓ VerifiedOE Reference Group: 5137130350, 513713-0350, 5-13713035-0 are consistently grouped as interchangeable references across multiple supplier catalogs.
• ✓ VerifiedFactory Number: 5-13713035-YH — confirmed as the factory/tooling reference for the ISUZU 4BD1 thermostat cover.
• ✓ VerifiedVehicle & Engine Coverage: ISUZU 4BD1 — confirmed by Yishan factory data across multiple language portals. ISUZU NFW220 excavator — confirmed by dedicated OTTO and Hitachi-Isuzu catalog listings. 4BC2, 4JG1, 4BA1 — referenced as suitable engine numbers in cross-application data.
• ✓ VerifiedMaterial: Aluminum and plastic — confirmed by Yishan factory specification ("aluminium og plastmaterialer" / "aluminiu și plastic"). One technical listing further specifies high-quality aluminum alloy for the cover material.
• ✓ VerifiedNet Weight: 0.25 kg — confirmed consistently across Yishan factory data in multiple languages.
• ✓ VerifiedActual Dimensions: 21 × 18 × 0.2 cm — confirmed by Yishan factory data.
• ✓ VerifiedWarranty Reference: 6 months (Yishan factory reference) / 3–12 months (OTTO reference) — confirm tier at inquiry.
• ✓ VerifiedMOQ Reference: 1 pc (OTTO reference) — sample-friendly ordering available.
• ✓ VerifiedHS Code Reference: 8409999990 — confirmed by OTTO catalog data for the 5-13713035-0 reference.
• ✓ VerifiedOrigin Reference: Japan (OTTO listing) / China aftermarket (Yishan listing) — multiple origin options available. Confirm origin preference at inquiry.
• ⚠ NotePrecise Thermostat Cavity Diameter NOT Publicly Published: The accessible supplier data does not publish the thermostat cavity bore diameter for 5137130350. The 21 × 18 × 0.2 cm dimension appears to be an overall size or packaging reference, not the cavity bore. Measure the original cover or confirm against the thermostat part number before ordering if precision matching is required.

• Coolant leak at the thermostat cover joint: Visible drips, dampness, or crusty residue (white/pink coolant crust) around the cover-to-housing interface — the most direct sign of a failed gasket, warped sealing surface, or cracked cover.
• Overheating or temperature fluctuation: A cover 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.
• Deformed or cracked plastic housing section: The plastic portion of the cover can age, deform, or crack under sustained thermal cycling.
• Thermostat not seating properly: A distorted cover cavity can prevent the thermostat from sealing, causing continuous coolant bypass and extended warm-up times.
• Visible corrosion or pitting on the aluminum cover sealing surface: The aluminum cover can corrode at the coolant passage edges, preventing the gasket from sealing even when new.

• Engine and equipment code are the first checks: The primary engine is 4BD1, and the primary equipment is the NFW220 excavator. Cross-reference data extends to EX100/EX120/EX150 series and additional Hitachi models. Confirm the engine code and equipment model against the machine documentation before ordering.
• Cover / cap only — thermostat is separate: This is the cover/cap only. The thermostat element is not included. Confirm the required scope before ordering.
• Material and origin vary by supply channel: Primary material is aluminum + plastic. Origin may be Japan (OTTO) or China (Yishan). Specify material and origin preference at inquiry if required for the application.
• Cross-reference engine coverage (4BC2/4JG1/4BA1) requires physical verification: While these engine numbers appear in cross-reference data, do not assume direct interchangeability without confirming the thermostat cover's mounting and cavity dimensions against the original unit.

1. Confirm the required part first: Verify the engine code (4BD1) and equipment model (NFW220 / EX-series). Confirm whether the replacement is a cover/cap 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.
6. Install the new cover with a new gasket: Seat a new gasket, position the 5137130350 cover, and insert the mounting bolts. Do not over-torque — the plastic 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) — 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 corrosion of the aluminum cover and degradation of the plastic housing.
• Replace the cover if the sealing surface is pitted, the cavity is distorted, or a crack is detected in the plastic housing section.

• Standard packing: Wooden box / standard packing with safety (OTTO reference); neutral or customer-branded packaging available.
• Package contents: 1 × Thermostat Cover. Thermostat element is NOT included unless explicitly stated — confirm at inquiry.
• Set options: Cover only (standard) / cover + thermostat + gasket kit (where available) — specify at inquiry.
• Suitable for: ISUZU 4BD1 engine repair shops, NFW220 / EX-series excavator service providers, construction machinery maintenance departments, spare parts distributors, and export wholesalers.