Positive Crankcase Ventilation: Testing and Inspection

CDR Valve Operation:

CDR Valve Test:

The purpose of the CDR valve is to maintain 0.75-1.0 kPa (3-4 inches of water) vacuum in the crankcase. Too little vacuum will tend to force oil leaks. Too much vacuum will pull oil into the air crossover.

The CDR valve is checked with a water manometer. The U-tube manometer indicates pressure or vacuum by the difference in the height of two columns of fluid.

Connect one end of the manometer to the engine oil dipstick hole. The other end of the manometer is vented to atmosphere.

Install air cleaner and run engine at idle.

One inch (1") water pressure at idle to approximately 3-4 inches water vacuum at full load. Add the amount that the manometer column travels up, to amount column travels down to obtain total PSI/Vacuum.

Example:
One-half inch above zero plus one-half inch below zero equals one inch vacuum reading.
1/2" + 1/2" = 1"