The hydraulic oil of ZF automatic transmission is cooled by the coolant of the engine system. If the amount of coolant entering the hydraulic oil radiator is small, the hydraulic oil will not be sufficiently cooled and heat up. If the hydraulic oil system does not circulate smoothly, the temperature of the hydraulic oil will rise too quickly. Reasons for poor circulation of hydraulic oil: (1) Insufficient amount of hydraulic oil; (2) Hydraulic oil pipe is blocked; (3) Hydraulic oil radiator is blocked; (4) The internal circulation pump is drained. The transmission hydraulic oil system needs to be diagnosed: (1) The oil volume is in the middle of the scale, which proves that the oil volume is sufficient; (2) The circulating pump has a working sound, which proves that the circulating pump is working, but it cannot prove whether there is oil leakage inside the circulating pump; (3) Disassemble the oil pipe joint of the return transmission, the circulating pump enters the working state, and observe the oil return flow of the oil pipe. It is found that the return oil flow is normal, which proves that the circulating pump is working normally, and the hydraulic oil pipe and the hydraulic oil radiator are not blocked.
Diagnosis conclusion: Find out the reasons for insufficient coolant entering the ZF automatic transmission radiator: (1) Thermostat failure; (2) Engine water pump head is small; (3) Water inlet and outlet pipes are blocked; (4) Engine internal water channels are blocked; ( 5) The internal water pipe of the radiator is blocked; (6) The internal water pipe of the radiator of the ZF automatic transmission is blocked; Diagnose the engine cooling system: (1) Disassemble and inspect the thermostat, the thermostat can be fully opened in the water of 82℃, which proves the thermostat Work normally; (2) Detect the flow of engine coolant. During the test, no thermostat is installed in the engine cooling system. Observe from the engine radiator water return port. The engine is running at idle speed and the coolant flow rate is observed. At the beginning, the flow rate is normal. After about 15L of coolant is discharged, the flow rate begins to decrease. The test proves that: ①The head of the water pump meets the requirements; ②The water outlet pipe from the engine to the engine radiator is not blocked; ③The water channel in the engine cylinder circulates smoothly; There is a blockage in the water pipe from the radiator, the engine radiator to the ZF automatic transmission radiator, the ZF automatic transmission radiator, and the water pipe from the ZF automatic transmission radiator to the engine water pump.
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