Crankcase Pressure Check

- Tools Required
- SA9127E Gauge Bar Set





High crankcase pressure indicates an excessive amount of air passing between the rings and cylinder walls into the crankcase. A loss of engine lubricating oil into the air intake tube/filter housing or out the dipstick hole is indicative of excessive crankcase pressure. High negative pressure or vacuum can be caused by a plugged air filter element or restricted air intake.

CAUTION: THE CRANKCASE PRESSURE CHECK MUST BE PERFORMED WITH THE VEHICLE IN PARK OR NEUTRAL AND PARKING BRAKE APPLIED.

Test method:
1. Remove the dipstick and connect a 0-15 kPa gauge (0-16 inch H2O manometer or magnahelix in gauge bar kit SA9127E) to the dipstick tube.
2. Operate the engine until it reaches normal operating temperature and observe the crankcase pressure at 4,000 RPM.
3. The crankcase pressure should not exceed:
New Engine:
Positive: 1.0 kPa (4.0 inch H2O) Max.
Negative: 3.0 kPa (12.0 inch H2O) Max.
Used Engine:
Positive: 2.5 kPa (10.0 inch H2O) Max.
Negative: 3.5 kPa (14.0 inch H2O) Max.
4. If the crankcase pressure exceeds specifications, ensure the PCV system is functioning properly.

IMPORTANT: It may be necessary to complete a compression and cylinder leakage check for evaluation of piston rings and cylinder walls when there is high (positive) crankcase pressure. Low (negative) crankcase pressure indicates a possible restricted air intake system.