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Why is there oil in the coolant for this diesel generator?

April 20, 2022
Coolant, also known as antifreeze coolant, antifreeze can prevent the coolant from freezing and bursting the radiator and freezing the diesel engine cylinder block when the diesel generator set stops in the cold season, but we have to correct a misunderstanding, antifreeze is not only winter It should be used all year round.
Recently, users have reported that the diesel engine of the generator set has gradually found that there is oil bloom in the radiator during use. With the passage of time, more and more oil splashes in the radiator, and the radiator overflows from the water inlet, and the phenomenon of water overturning in the radiator is also increasing. What is the reason for this?
Troubleshooting: Checked the cylinder head gasket, oil cooler, torque converter cooler, no problem. There is no reduction in transmission oil in the transmission, and there is no water in the diesel engine oil, just a little less.
Since the user's diesel generator set is used on the construction site and the construction site conditions are limited, the oil cooler and torque converter cooler in use of the same model were first replaced. After running for 1h, the fault still exists. Remove the cylinder liner and observe that there is no abnormality on the surface of the cylinder head. Use a steel ruler to stand up and check the plane of the cylinder head. There is no deformation, there is little carbon deposition in the piston combustion chamber, and the combustion is normal. Take out 6 cylinder liners for inspection, the wear is normal, the surface has no blisters and no deformation. During the re-test operation, there was no oil splash in the radiator at the beginning. After the coolant temperature rose to 70°C, the oil splash began to appear, and the higher the coolant temperature, the more oil splash. Carefully check the cylinder head again, remove the water baffles on both sides of the cylinder head, observe the inside of the water channel, and find nothing abnormal, but there is a small amount of oil in the coolant overflowing from the water channel.
Cause of failure: After starting the diesel engine, carefully observe the internal conditions of the water channel. It is found that black oil filaments float from the water baffle on the side of the exhaust pipe of the cylinder head of cylinder 1 and cylinder 2. Oil spills from tiny blisters. This trachoma communicates with the oil passage. When the machine does not start, the pressure on both sides is balanced; after starting, the pressure of the oil is higher than the pressure of the water. The oil flows into the circulating coolant under the action of the pressure difference.
Troubleshooting: After replacing the cylinder head, the fault disappeared.