When the engine temperature is too high, it usually looks for the fault from the circulation circuit of cooling water, and then looks for it from other aspects. If the temperature of the body is the same as the temperature of the water tank, open the lid of the tank and check the flow rate of the cooling water, it indicates that the circulation circuit of the cooling water is not fault. If the cooling water is not flowing or the flow is not smooth, the circulation circuit of the cooling water is found to be malfunction. The circulation loop of the cooling water can be proved to be malfunction, if there is no pressure on the hose (water is not flowing, no circulation). The water tank insulation curtain and shutter are the regulating devices for cooling intensity. The diesel engine equipped with insulation curtain or shutter does not adjust in time when the water temperature is too high, resulting in the reduction of the air flow rate through the radiator, resulting in poor heat dissipation. Check whether the heat insulation curtain or shutter is lowered, the insulation curtain will be opened, and the water temperature will gradually drop to normal.