8981587781 Excavator Isuzu 6HK1 Engine Thermostat

Part number 8981587781 (also written as 8-98158778-1, commonly referred to as cross part number 8981587780) is the original coolant thermostat (commonly known as the water tank/thermostat, T-82) for Isuzu 6HK1 series diesel engines, located at the outlet/thermostat housing of the engine cooling system. It is mainly shipped with 6HK1 (including variants such as AA-6HK1T), so it is commonly seen in the ZX series equipped with 6HK1 in the Hitachi system, such as ZX330-3, ZX360H-3G, etc. However, there may be differences in shell/gasket versions for 6HK1 in different batches. When purchasing, the original part number 8981587781 must be used as the standard, and the engine nameplate model and serial number must be checked (old part photos should be provided if necessary) to avoid mixing thermostats with different opening temperatures or flange sizes.

This is a wax thermostat: the core valve disc is sealed with micro paraffin capsules, and the volume change drives the main valve to rise and fall when the temperature changes, thereby switching the coolant "small cycle/large cycle", stabilizing the engine operating temperature in the high-efficiency range of about 82 ° C opening (T-82) and nearly 95 ° C fully open. The material and dimensional tolerances of the original valve body and sealing surface are controlled, and with the specified form of sealing gasket/sealing surface (flange clamping structure), it can maintain correct opening characteristics and leak free sealing for a long time under vibration, pressure pulse, and coolant chemical environment.

Before suspecting the thermostat, first eliminate the appearance: check whether the water temperature gauge/alarm is really abnormal, and confirm that the water tank is not blocked, the fan coupling/belt is normal, the coolant volume is sufficient, and there is no large amount of air (air can cause false "thermostat jamming"). When disassembling, be sure to wait for complete cooling and pressure relief; The old gasket/adhesive must be cleaned thoroughly, and the new part should be seated in the correct direction (usually with markings/bypass holes facing the correct side); Tighten the bolts of the water outlet pipe in a cross order and with the specified torque (the common value in the manual is about 19 N · m), without saying 'the tighter the better'. After installation, replenish the fluid and exhaust the air, and heat up the water temperature. Confirm that the pointer is stable in the normal working area and there is no leakage at the joint.