4.9.3 Pressure reducing valve
The pressure reducing valve serves to limit the oil pressure in the oil passages of the lubrication system. The oil pressure can rise when the engine speed is too high, or when the oil is too thick, for example in a cold engine. The pressure reducing valve is usually installed in the pump casing. It is a ball, which is pressed by a spring. While the oil pressure is normal - the ball is pressed tightly against the spring. When the pressure starts rising excessively, the ball moves, compressing the spring, thus opening the bypass channel through which the oil from the sump through the pump again flows into the sump.
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