Thermostat Housing 8-97139602-0 / 8971396020 For ISUZU NKR55 NHR NKR NPR NQR QKR (4JB1 / 4JG2) — Metal Construction, 0.8 Kg, OEM-Spec

The Thermostat Housing with OEM references 8-97139602-0 / 8971396020 is a verified replacement cooling-system component for ISUZU NKR55, NHR, NKR, NPR, NQR, and QKR light trucks equipped with 4JB1 (2.8L) and 4JG2 (3.1L) diesel engines. This housing is the structural seat and enclosure for the engine thermostat — it fixes the thermostat in position, forms the sealed coolant cavity against the cylinder head, and provides the mounting interface for the coolant outlet pipe.

The unit is manufactured from metal (per supplier material specifications) and is supplied as a brand-new OEM-specification aftermarket component. The net weight is 0.8 kg per unit, with a minimum order quantity as low as 1 pc accepted by some supply channels. A Taiwan-origin variant (8971396020CH) is also referenced in the aftermarket, providing an alternative sourcing path with a different quality baseline.

This housing is confirmed for both the 4JB1 (2.8L) and 4JG2 (3.1L) diesel engines across the ISUZU N-Series platform. The application matrix includes NHR 4JB1/4JG2 (1994+), NKR 4JG2 (1993+), NKR 4JB1 (1994+), NPR/NQR 4JG2 (1994–1998), NPR/NQR 4JB1 (1999–2002), and QKR 4JB1 (2011+). Confirm the engine code and model year before ordering.

This listing covers the thermostat housing only. The thermostat element (e.g., 8-97361-770-0, 82°C) and the thermostat cover are separately supplied and are not included. For a complete cooling-system repair, order the thermostat and cover as required.

The primary references 8-97139602-0 / 8971396020 are grouped with 8971396021 and 8971396020CH (Taiwan variant) in the aftermarket. The 8971396021 reference is also used for NKR94 4JG2 applications, indicating platform overlap across N-Series variants. Confirm the original housing marking where possible. View related reference listing.

• OE Reference & Engine Coverage Verified: 8-97139602-0 / 8971396020 is confirmed for ISUZU 4JB1 and 4JG2 engines across NHR, NKR, NPR, NQR, and QKR models.
• Material Verified: Metal — confirmed by supplier material specifications in Turkish, Russian, and Italian language listings.
• Net Weight Verified: 0.8 kg — confirmed consistently across Polish, Vietnamese, Arabic, and other language portals.
• Component Type & Function Verified: Identified as "MIESZKANIA;TERMOSTAT" (thermostat housing) and "温度調節座席" (thermostat seat) — a component used to install the engine thermostat.
• Vehicle Application Matrix Verified: NHR 4JB1/4JG2 (94–), NKR 4JG2 (93–), NKR 4JB1 (94–), NPR/NQR 4JG2 (94–98), NPR/NQR 4JB1 (99–02), QKR 4JB1 (11–).
• Cross-Reference Density Verified: 8971396020, 8-97139602-0, 8971396021, and 8971396020CH are grouped as interchangeable or related references across multiple catalogs.
• Warranty & MOQ Reference: 3-month warranty; small quantity accepted with quantity discount — confirmed by supplier data.
• Alternative Origin Verified: Taiwan-origin variant (8971396020CH) is available as an alternative supply channel with a different quality baseline.

• Coolant leak at the thermostat housing joint: Visible drips, dampness, or crusty residue (white/pink coolant crust) around the housing-to-cylinder-head interface or the housing-to-outlet-pipe connection — the most direct sign of a failed gasket or a warped/corroded housing sealing surface.
• 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 vehicle: Dried coolant around the thermostat area indicates a slow weep that should be addressed before it becomes a sudden failure.
• Visible corrosion or pitting on the housing sealing surface: The metal housing can corrode at the coolant passage edges, preventing the gasket from sealing even when new.
• Cracked or deformed housing: Impact damage or over-torquing of the mounting bolts can crack the metal casting, 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.

• Engine code and model year are the first checks: The application matrix spans 4JB1 and 4JG2 engines across multiple N-Series models and year ranges. Confirm the engine code and model year against the vehicle documentation before ordering.
• Housing only — thermostat and cover are separate: This is the housing only. For a complete repair, order the thermostat (8-97361-770-0, 82°C reference) and thermostat cover separately as required.
• Taiwan variant available: 8971396020CH is a Taiwan-origin variant that may offer a different quality baseline. Specify origin preference at inquiry if applicable.
• 8971396021 cross-reference caution: The 8971396021 reference is also used for NKR94 4JG2 applications. While grouped as a related reference, do not assume it is dimensionally identical to 8-97139602-0 without physical verification.

1. Confirm the required part first: Verify that the original housing is the correct unit for the 4JB1 or 4JG2 engine and model year. Confirm whether the thermostat and cover are being reused or replaced.
2. Cold engine only: Allow the engine to cool fully before opening the cooling system. Drain coolant to a level below the thermostat housing.
3. Remove the old housing: Disconnect the coolant outlet pipe and any bypass hoses. Unbolt the housing from the engine. Note the orientation of the thermostat and any seals.
4. Clean the mating surface: Remove all old gasket residue and corrosion from the engine face and the housing 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 for the application (82°C reference).
6. Install the new housing with a new gasket: Seat a new gasket, position the 8-97139602-0 housing, and insert the mounting bolts.
7. Torque in sequence: Tighten the housing bolts evenly in a cross pattern to the workshop manual specification. Do not over-torque — the housing or engine face can distort.
8. Reconnect the pipe and refill coolant: Reconnect the outlet pipe and any bypass hoses. Refill with the correct coolant mixture and bleed the system according to the ISUZU procedure.
9. Run and verify: Start the engine, bring it to operating temperature, and check for leaks at the housing joint and pipe connection. Confirm the temperature gauge stabilizes.

• Inspect the housing joint at every coolant service or every 20,000–30,000 km — look for crusty residue or dampness.
• Replace the gasket whenever the housing is removed — gaskets are single-use compression seals.
• Flush coolant according to the manufacturer interval. Degraded coolant accelerates housing corrosion.
• Replace the housing if the sealing surface is pitted or warped.

• Standard packing: Neutral box / Color box / Customer-branded packaging — confirmed by supplier terms.
• Package contents: 1 × Thermostat Housing. Thermostat and thermostat cover are NOT included unless explicitly stated — confirm at inquiry.
• Set options: Housing only (standard) / housing + gasket set (where available) — specify at inquiry.
• Suitable for: ISUZU NKR55 / NHR / NKR / NPR / NQR / QKR cooling-system repair shops, light commercial fleet maintenance departments, spare parts distributors, and export wholesalers.