Nissan Sentra/Pulsar/NX 1982-1996 Repair Guide

Crankcase Ventilation System



See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: Crankcase emission control system diagram-CD17 diesel engine

The closed-type crankcase emission control system prevents blow-by gas from entering the atmosphere and keeps the internal crankcase pressure constant.

During engine operation, the blow-by gas is fed into the intake manifold by the crankcase emission control valve. When the intake air flow is restricted by the throttle chamber, the internal rocker cover pressure decreases. The valve keeps the engine pressure constant, so that air or dust is not sucked in around the crankshaft seals.


See Figures 2 and 3

Click image to see an enlarged view

Fig. Fig. 2: Air should flow through the control valve, in the direction indicated

Click image to see an enlarged view

Fig. Fig. 3: Cover the indicated passage. With suction applied to the other port, the control valve should make a clicking sound

Inspect the hoses; if necessary, use compressed air to unblock them. If the hoses are damaged or extremely dirty, replace them.

  1. Remove the crankcase emission control valve from the top of the rocker cover.
  3. Blow air from the rocker cover side of the valve, and make sure that air flows from the intake manifold side.
  5. Close the rocker cover side of the valve and suck on the pipe, to make sure that the diaphragm makes a clicking sound.
  7. If the valve does not perform as specified, replace the valve.