Tools Required
SA9127E Gage 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 the parking brake applied.
Test method:
- Remove the dipstick and connect a 0-15 kPa gage (0-16 in H2O) manometer or magnahelix in the SA9127E Gage Bar Set to the dipstick tube.
- Operate the engine until it reaches normal operating temperature and observe the crankcase pressure with engine at 4,000 RPM.
- The crankcase pressure should not exceed:
- If the crankcase pressure exceeds specifications, ensure the PCV system is functioning properly.
Crankcase Pressure (New Engine)
| • | Positive: 1 kPa (4 in) H2O Max. |
| • | Negative: 3 kPa (12 in) H2O Max. |
Crankcase Pressure (Used Engine)
| • | Positive: 2.5 kPa (10 in) H2O Max. |
| • | Negative: 3.5 kPa (14 in) H2O Max. |
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.
Postive Crank Case Ventilation (PCV) System
Always Perform a Visual Check of the PCV System:
| • | Properly mounted PCV valve, firmly seated in the grommet on rocker arm cover |
| • | PCV Hose, grommet, fresh air hose, and clamps in place, no damage to PCV hose, rocker arm cover grommet, fresh air hose. Ensure the clamps are on tight. |
CONDITION | POSSIBLE CAUSE | CORRECTION |
|---|---|---|
Rough Idle, Stalling or Slow Idle Speed, Oil Leaks, Oil in Throttle Body/Plenum, or Sludge in Engine. | 1. Clogged hose. | 1. Repair or replace hoses as necessary. |
2. Clogged PCV valve. | 2. Replace PCV valve. | |
Rough Idle, Stalling, or High Idle Speed. | 1. Leaking hose. | 1. Replace hose. |
2. Leaking PCV valve. | 2. Replace PCV valve. |
Functional Check
If engine is idling rough, check for a clogged PCV valve or hose. Check the PCV valve identification number to be sure the correct valve is installed. Replace as required.
Use the following procedure to determine if the PCV valve is functioning properly:
- Remove PCV valve from cam cover grommet.
- Run engine at idle.
- Place your thumb over end of PCV valve to check for strong vacuum signal. If there is no vacuum present, check for clogged hose, plugged valve or plugged intake manifold port. Replace any clogged components or clean out plugged port.
- Turn off engine and remove PCV valve from hose. Shake valve and listen for the plugger to rattle inside the valve. If valve does not rattle, replace valve.
Other Crankcase Ventilation System Faults
If there is evidence of engine oil in the throttle body or air cleaner and all the PCV components appear and function properly it may indicate excessive crankcase pressure. Refer to "Engine Diagnostic" section in this service manual for specific procedure to perform a crankcase pressure check.
