What are the causes of crankshaft one-way valve failure?

[DeHenry]

Crankshaft one-way valve failure may be caused by blockage of the one-way valve spring. Function of the one-way valve: The one-way valve is a component in the crankcase ventilation system, installed inside the engine, and its role is particularly important. Once it malfunctions, it can affect the normal operation of the engine. During normal engine operation, a portion of the combustible mixture and exhaust gases leaks into the crankcase through the gaps between the piston, piston rings, and cylinder wall. These gases are at high temperatures and carry fuel molecules and other impurities, causing the engine oil to gradually oxidize, deteriorate, and dilute under high temperatures. The gases entering the crankcase increase the internal pressure, leading to oil leaks from seals and gaskets. Therefore, it is essential to promptly vent these gases from the crankcase. Hence, early engines were equipped with a crankcase ventilation system. Types of crankcase ventilation systems: Natural ventilation: Natural ventilation involves installing a downward-facing exhaust pipe on the crankcase. The outlet of the exhaust pipe is shaped into a slant cut opposite to the direction of vehicle travel. The airflow from the vehicle's movement and the cooling fan creates a certain vacuum at the exhaust pipe outlet, drawing gases out of the crankcase. Fresh air enters the crankcase through the intake pipe. Both the intake and exhaust pipes have filters to prevent external dust from entering the crankcase and to block the escape of oil mist from the crankcase. Forced ventilation: One end of the one-way valve is connected to the valve cover, as the valve cover interior communicates with the crankcase, and crankcase pressure is directly reflected in the valve cover. The other end of the one-way valve is connected to the intake manifold. During engine operation, the pressure in the intake manifold is lower than that in the valve cover, creating suction that draws excess gases from the valve cover into the intake manifold, which are then sent to the combustion chamber. At the top of the crankcase, there is a pipe connected to the air filter, which serves as the crankcase's intake pipe, forming a closed loop for the forced ventilation system.