Is it normal to have oil inside the exhaust valve?
2 Answers
It is abnormal to have oil inside the exhaust valve, which may be caused by aging of the crankcase ventilation valve or faults in the piston, cylinder liner, piston pin, and piston rings, resulting in loss of their original sealing effect and leading to oil spraying. The reasons for oil in the exhaust pipe may include severe wear between the valve stem and valve guide, creating excessive clearance and causing oil to leak downward. The exhaust valve, also known as the oil separator or pressure control valve, is installed between the compressor outlet and the condenser inlet. Through separation, it improves the heat transfer effect in the condenser and evaporator. The working principle of the exhaust valve: High-pressure gas (gaseous working medium and lubricating oil) from the compressor enters the exhaust valve and then the guide vanes of the exhaust valve, flowing in a spiral pattern along the vanes. By centrifugal force and gravity, the lubricating oil is separated from the working medium gas and flows down along the inner wall of the cylinder. The working medium gas is led out of the exhaust valve through a multi-hole baffle via the central pipe. The separated lubricating oil accumulates in the lower part of the oil separator and can be periodically discharged or automatically returned to the compressor's crankcase using a float valve.
I've been repairing cars for most of my life and have seen too many cases of oil in the exhaust valve. It's not exactly normal, but it's nothing to make a big fuss about either. Usually, it's because the engine oil inside gets blown into the exhaust system by the crankcase ventilation system, accumulating bit by bit until it enters the valve. If it's just a thin layer of oil residue, it's not a big deal, and most cars will be fine after driving for a while. However, if there's so much oil that it turns into sludge, it's likely a sign of engine trouble, such as worn piston rings or faulty valve seals. In that case, the car may burn oil, emit blue smoke, or even suffer from insufficient power. It's advisable to check the oil consumption promptly, perform regular engine inspections, or simply replace the exhaust valve to prevent jamming. Don't wait until the car shakes badly to take action—routine maintenance can save a lot of trouble.
