Thermostat Housing 8971044401 8943822020 8971172430 8973729941 For ISUZU TFR54 4JA1 4JB1 4JG2 — OEM-Grade Aluminum Die-Cast, Direct Fit Cooling Housing

The Thermostat Housing covering OEM references 8971044401, 8943822020, 8971172430, and 8973729941 is a verified replacement cooling-system component for ISUZU TFR54 pickups equipped with the 4JA1 (2.5L) diesel engine, with broader platform coverage extending to 4JB1, 4JG2, and 4JH1 engine families in related TFR/TFS and D-MAX applications. This housing is the structural seat and enclosure for the engine thermostat, responsible for holding the thermostat securely in position, forming the sealed coolant cavity against the cylinder head, and providing the mounting interface for the water outlet pipe and bypass circuit.

The part is manufactured from aluminum die-cast construction, a material choice that provides dimensional stability and corrosion resistance in the hot coolant environment while maintaining the flat sealing surface required for the thermostat gasket. The factory tooling reference for this housing is 8-97104440-GC, which serves as a cross-check number against the four OEM references listed. The four OEM numbers (8971044401, 8943822020, 8971172430, 8973729941) are consistently grouped as alternative or generation references for the same thermostat housing application across multiple independent supplier catalogs, meaning they are treated as functionally interchangeable in the aftermarket for the TFR54 4JA1 application.

• OE Group Verified: 8971044401 / 8943822020 / 8971172430 / 8973729941 are listed as a unified OE number group for the ISUZU TFR54 thermostat housing across multiple Yishan Auto Parts language portals (Slovenian, Vietnamese, Pakistani, Dutch).
• Part Name Verified: ISUZU catalog entries confirm 8971172430 as "HOUSING THERMO" and 8973729941 as "HOUSING; THERMOSTAT", establishing the component type as a thermostat housing, not a cover or pipe.
• Material Verified: Aluminum — an independent B2B listing describes the TFR thermostat housing/seat for 8973729941 / 8-97104440-GC / 8971044400 as "aluminyum" (aluminum).
• Factory Tooling Reference Verified: 8-97104440-GC is the factory number associated with this housing, alongside the OE group.
• Engine & Vehicle Coverage Verified: Confirmed for TFR54 4JA1, with catalog coverage extending to 4JA1-TC, 4JB1, 4JG2, and 4JH1 engines in TFR/TFS and D-MAX platforms.
• Companion Components Identified: Thermostat (8-97361-770-0 82°C; 8-98017-027-2 85°C), thermostat housing gasket (8-97212-537-1 / 8-98114-587-0), outlet pipe (8-97355-456-7), and bypass pipe (8-98165-518-0 / 8-98165-517-1) are documented adjacent components in the same ISUZU parts diagram.
• Net Weight Not Publicly Disclosed: Public supplier listings for this exact housing group do not publish a net weight figure. Packaging dimensions of 17.7 × 10.5 × 8 cm (or 20.3 × 11 × 8.1 cm for the carton) are available as logistics reference only. Confirm net weight at inquiry for freight and inventory planning.

• 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 joint — 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 or in stop-and-go commercial driving.
• 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: Aluminum housings can corrode at the coolant passage edges, preventing the gasket from sealing even when new.
• Cracked or deformed housing: Impact damage or over-torqueing of the mounting bolts can crack the aluminum casting, requiring replacement.
• Repeated coolant loss without an obvious external leak: A compromised housing joint can allow coolant to seep slowly, producing unexplained reservoir level drops.
• Thermostat not seating properly: A distorted housing cavity can prevent the thermostat from sealing, causing continuous coolant bypass and extended warm-up times.

• Four OE numbers — confirm the physical marking: The numbers 8971044401, 8943822020, 8971172430, and 8973729941 are grouped as interchangeable references for the same TFR54 4JA1 housing application. However, read the original unit's casting or part marking where possible. If the original is marked with a specific suffix, match it.
• Housing vs. Cover vs. Pipe: This is the thermostat housing (seat). It is not the water outlet pipe (8-97355-456-7) and not a simple cover plate. Compare the original unit's shape — it should have a cavity for the thermostat and mounting provisions for the outlet/bypass components.
• Gasket is not included: The thermostat housing gasket (8-97212-537-1 / 8-98114-587-0) is a separate component. Always use a new gasket when installing the housing. Confirm whether the supplier includes a gasket at inquiry.
• Aluminum sealing surface: Aluminum housings are sensitive to over-torqueing. Uneven or excessive bolt torque distorts the sealing flange and causes leaks. Use a torque wrench and follow the workshop manual sequence.

1. Confirm the required component first: Verify that the original unit is the thermostat housing (seat), not the water outlet pipe or a cover plate. Compare the physical shape and cavity against the replacement.
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 outlet pipe and any bypass hoses. Unbolt the housing from the cylinder head. Note the orientation and the position of the thermostat.
4. Clean the mating surface: Remove all old gasket residue and corrosion from the cylinder head 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 (82°C or 85°C per application).
6. Install the new housing with a new gasket: Seat a new gasket (8-97212-537-1 / 8-98114-587-0) on the cylinder head, position the 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 aluminum castings — excessive torque distorts the sealing surface and causes leaks.
8. Reconnect the outlet pipe and bypass hoses: Reconnect the water outlet pipe (8-97355-456-7) and any bypass hoses. Tighten fittings to specification.
9. Refill and bleed coolant: Refill with the correct coolant mixture and bleed the system according to the ISUZU procedure. Air pockets are a leading cause of post-replacement overheating.
10. Run and verify: Start the engine, bring it to operating temperature, and check for leaks at the housing joint and pipe connections. Confirm the temperature gauge stabilizes and the heater blows hot.

• 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 aluminum corrosion.
• Replace the housing if the sealing surface is pitted or warped — resurfacing an aluminum housing is not recommended for this application.

• Standard packing: Neutral carton (reference carton size 20.3 × 11 × 8.1 cm); custom packaging available on request.
• Package contents: 1 × Thermostat Housing. Gasket, thermostat, and mounting bolts are not included unless explicitly stated.
• Set options: Housing only / housing + gasket set / complete cooling kit (housing + gasket + thermostat) — specify at inquiry.
• Suitable for: ISUZU TFR54 / TFR/TFS pickup cooling-system repair shops, 4JA1/4JB1 engine rebuilders, light commercial fleet maintenance departments, spare parts distributors, and export wholesalers serving Southeast Asia, the Middle East, Africa, and Latin America.
• Related parts available: Thermostat (8-97361-770-0 / 8-98017-027-2), thermostat housing gasket (8-97212-537-1 / 8-98114-587-0), water outlet pipe (8-97355-456-7), bypass pipes (8-98165-518-0 / 8-98165-517-1), and complete 4JA1/4JB1 cooling-system kits.