Crankcase Ventilation Systems (Open Systems): Operation
Air enters system through oil filler cap and is circulated through engine. After circulating through the engine air is returned to intake manifold through an exhaust tube which extends from crankcase ventilation outlet in left side of the engine to a spring loaded regulator valve which regulates amount of air to meet changing operating conditions. The regulator valve is controlled by intake manifold vacuum. During idle, intake manifold vacuum is high. The high vacuum overcomes the tension of the spring pressure and seats the valve. With the valve in this position, all ventilating air passes through a calibrated orifice in the valve and there is minimum ventilation. As engine speed increases and manifold vacuum decreases, the spring forces valve off its seat to full open position which increases flow of ventilating air.