DRIVEABILITY AND EMISSIONS (DIESEL) 11-1

SECTION 11 CRANKCASE VENTILATION SYSTEM CONTENTS

General Description • 11-1 On-Vehicle Service 11-3 Diagnosis ... 11-2 CDR Valve and Hoses . • 11-3 CDR Valve Test 11-2 Parts Information • . 11-3

GENERAL DESCRIPTION

The crankcase ventilation system used on diesel The acts against a spring engines is designed to maintain a slightly negative loaded diaphragm to control the flow of crankcase crankcase pressure across the speed range. This lower gases (Figures 11 1 and 11-2). Higher intake vacuum pressure minimizes oil leaks. The system consists of a levels pull the diaphragm closer to the top of the outlet Crankcase Depression Regulator (CDR) valve, located tube. This reduces the amount of gases being drawn on the right valve cover. from the crankcase and decreases the vacuum level in The CDR valve is used to regulate (meter) the flow the crankcase. As the intake vacuum decreases, the of crankcase gases back into the engine. The valve is spring pushes the diaphragm away from the top of the designed to limit vacuum in the crankcase as the gases outlet tube allowing more gases to flow to the intake are drawn from the right valve cover, through the manifold. valve, and into the intake manifold (air cross-over).

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1 CRANKCASE VAPORS TO INDUCTION SYSTEM 1 COVER 2 RUNNERS 2 DIAPHRAGM

3 BLOWBY LEAKAGE AT VALVES AND 3 BODY 4 SPRING 4 CRANKCASE DEPRESSION REGULATOR VALVE 5 OUTLET TUBE (GASES TO INTAKE MANIFOLD)

X CRAN KCASE VAPORS 6 INLET PORT (GASES FROM CRANKCASE) 8S3982 6E 9S 5609 66

Figure 11-1 - Crankcase Vapor Flow Figure 11-2 - CDR Valve Operation 11-2 DRIVEABIUTY AND EMISSIONS (DIESEL)

DIAGNOSIS

CDR VALVE TEST 2 Install air cleaner. 3. Start engine and observe manometer reading. It The purpose of the CDR valve is to maintain 0.75 - should read zero to one inch (0-1") of water (vacuum) 10 kPa (3-4 inches of water) vacuum in the crankcase at idle to approximately 3-4 inches of water at 2000 RPM. Too little vacuum will tend to force oil (vacuum) at 2000 RPM. Add the amount that the leaks. Too much vacuum will pull oil into the intake manometer column travels up, to the amount that manifold. the column travels down to obtain total water The CDR valve is checked with a water manometer. pressure (vacuum). An example of a manometer The U-tube manometer (Figure 11-3) indicates reading is as follows. One-half inch above zero plus pressure or vacuum by the difference in the height of one-half inch below zero equals one inch vacuum the two columns of fluid. reading (1/2" + 1/2" = 1") (Figure 11-3)

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

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1 CDR VALVE 3 HOSE

2 INTAKE MANIFOLD 4 RIGHT VALVE COVER

8S 3981-6E Figure 11-4 -CDR Valve and Hoses (Non-Turbo)

1 CRANKCASE DEPRESSION REGULATOR VALVE

2 ENGINE OIL DIPSTICK TUBE

3 VENT TO ATMOSPHERE

4 MANOMETER-J 23951

5 1/2" ABOVE ZERO (SEE EXAMPLE)

6 1/2" BELOW ZERO (SEE EXAMPLE) 8S 3980-6E Figure 11-3 - CDR Valve Test DRIVEABILITY AND EMISSIONS (DIESEL) 11-3

ON-VEHICLE SERVICE

CDR VALVE AND HOSES PARTS INFORMATION Figures 11-4 and 11-5 PART NAME GROUP NOTICE: Do Not allow any solvent to come in contact with the diaphragm of the crankcase Valve, C/Case Depr Reg . . .. . 1.745 depression regulator valve, because the diaphragm Hose, C/Case Depr Reg VIv ...... 1.762 will fail.

The crankcase depression regulator valve is replaced as an assembly. Replace hoses as required, if inspection indicates cracks or decay. Refer to SECTION OB in appropriate service manual for diesel crankcase ventilation system maintenance requirements.

IT] HOSE pTI GROMMET NS15739 Figure 11-5 - CDR Valve and Hoses (Turbo) 11-4 DRIVEABILITY AND EMISSIONS (DIESEL)

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