8973007873 Original Isuzu 4HK1 Engine Thermostat for Excavator

Part number 8973007873 (also commonly written as 8-97300787-3) is a specialized part number for the original 4HK1 series diesel engine thermostat (commonly known as the "water tank") from Isuzu. This thermostat is the core temperature regulating component of the engine cooling system, responsible for automatically controlling the coolant circulation path (large/small circulation) based on the coolant temperature, ensuring that the engine quickly warms up and stabilizes at the optimal operating temperature. As an original standard component, it is mainly suitable for Hitachi hydraulic excavators equipped with Isuzu 4HK1 engine, such as Hitachi ZX200-3, ZX210H-3, ZX240-3, ZX270-3, ZX330-3, ZX350 and other models. In the aftermarket, this part often corresponds to the universal part number 1-87618431-0, or similar series such as 8-97300787-0, 8-97300790-2, etc.

This thermostat is a typical wax thermostat, belonging to the automatic temperature control valve of the engine cooling system. The core working principle is to use the thrust generated by the thermal expansion of internal precision paraffin components to drive the opening and closing of the main valve. When the engine is cold started, the coolant temperature is low, the volume of paraffin is small, the main valve is closed, and the auxiliary valve is opened. The coolant only undergoes a "small circulation" inside the engine, allowing the engine to quickly heat up to the optimal operating temperature (usually starting at 82 ° C or 85 ° C). As the water temperature rises, the paraffin expands, the main valve gradually opens, and the auxiliary valve gradually closes. The coolant flows through the radiator for a "large circulation" to prevent the engine from overheating. As an original component, it adopts high-precision paraffin formula, high-temperature resistant rubber sealing ring, and corrosion-resistant metal shell, ensuring precise opening temperature, stable flow characteristics, excellent durability, and reliable sealing performance. It is a key component to ensure that the 4HK1 engine always operates in the efficient and low wear temperature range.

The maintenance core of this thermostat lies in regular functional checks, seizing replacement opportunities, and standardizing replacement operations. It is recommended to check every 4000 working hours or every 2 years, and replace immediately if performance degradation or failure is found. Standardized replacement: Before replacement, be sure to wait for the engine to completely cool down and drain some of the coolant. When disassembling the thermostat housing, it is necessary to loosen the bolts in order and remove the old thermostat and sealing gasket. Before installing a new thermostat, the mounting surface must be thoroughly cleaned to ensure that there are no residual gaskets or dirt. Pay attention to the direction of the thermostat during installation (usually marked with "TOP" or arrow pointing towards the engine), and use a new original gasket to cross tighten the housing bolts to the specified torque. Finally, refill the designated model of antifreeze and start the engine to empty the air from the cooling system, checking for leaks. It is recommended to have professional maintenance personnel operate to ensure installation quality.