What is the reason for blow-by gas at the engine oil filler port?
2 Answers
The reason for blow-by gas at the engine oil filler port is: After the engine is ignited, the crankcase will have a certain pressure, and the oil pump will also pump oil to the cylinder head, which is a normal phenomenon. Fuel must be clean: If the fuel contains a high amount of impurities, it will accelerate the wear of the electric fuel pump and reduce its service life. If the fuel is not clean, it can also cause clogging of the fuel filter and fuel injectors, affecting the fuel supply pressure and normal injection volume, thereby reducing the engine's performance. Correct selection of fuel: The engine has high requirements for fuel quality and grade, and the requirements for electronic fuel injection engines are even higher. For cars equipped with catalytic converters and oxygen sensors, only unleaded high-grade gasoline can be used. If leaded gasoline is used, the exhaust catalytic converter will fail after driving more than 400 kilometers, the oxygen sensor will also malfunction, and the normal operation of the engine will be affected.
My old Passat also had blow-by issues last year. The mechanic said to mainly check three areas: First, the piston rings weren't sealing properly, allowing high-pressure exhaust gases to leak from the cylinders into the crankcase, with nowhere to go but to puff white smoke from the oil filler; second, severe cylinder wall wear, where you could feel obvious steps by running a finger along the walls; and third, a clogged crankcase ventilation valve, as older cars tend to accumulate sludge that blocks the ventilation pipes. The mechanic mentioned this condition often comes with oil burning, with blue smoke coming from the exhaust pipe too. In the end, it cost a pretty penny to replace the piston ring set to fix it, along with cleaning the entire ventilation system.
