Ford Escort/Tracer 1991-1999 Repair Guide

Crankcase Ventilation System



See Figure 1

The Positive Crankcase Ventilation (PCV) system vents blow-by gases from the crankcase back into the intake manifold where they are burned.

The PCV valve varies the amount of blow-by gas fed to the intake manifold in relation to engine demand and also prevents combustion backfiring from traveling into the crankcase.

The amount of blow-by gas allowed into the intake manifold from the crankcase is controlled by the PCV valve. The PCV valve acts like a one-way check valve and does not allow anything from the intake manifold to pass into the crankcase.

Click image to see an enlarged view

Fig. Fig. 1: Various designs of common PCV valve assemblies


  1. With the engine OFF , remove the PCV valve.
  3. Shake the PCV valve.
  5. If the valve rattles when shaken, re-connect it.
  7. If it does not rattle, replace it.
  9. Start the engine and allow it to idle. Disconnect the hose from the air cleaner or air outlet tube (the tube which connects the Mass Air Flow sensor and the throttle body).
  11. Place a piece of paper over the end of the hose. The vacuum should hold the paper in place.
  13. If vacuum does not exist, the system is plugged or the evaporative valve is leaking.
  15. Disconnect the evaporative hose, cap the tee and recheck the system. If vacuum exists, the PCV system is functioning. Check the evaporative emission system.
  17. If vacuum still does not exist at the PCV, check for vacuum back through the system (filler cap, PCV valve, hoses and the rocker cover bolt torque). Service the defective components as required.


For details on PCV valve removal and installation, refer to General Information & Maintenance .

Remove the PCV hoses by pulling and twisting them from their ports. Always check the hoses for clogging, breaks and deterioration.