Oil Pressure Diagnosis and Testing

Tools Required

• J 21867  Pressure Gage and Hose Assembly
• J 42907  Oil Pressure Tester

Fig 1: Measuring Oil Pressure Using J 42907
Courtesy of GENERAL MOTORS CORP.
1. With the vehicle on a level surface, run the vehicle for a few minutes, allow adequate drain down time (2-3 minutes) and measure for a low oil level.
2. If required, add the recommended grade engine oil and fill the crankcase until the oil level measures full on the oil level indicator.
3. Run the engine briefly (10-15 seconds) and verify low or no oil pressure on the vehicle gage or light.
4. Listen for a noisy valve train or a knocking noise.
5. Inspect for the following:
   • Oil diluted by water or glycol (anti freeze)
   • Foamy oil
6. Remove the oil filter and install the J 42907  .
7. Install J 21867  or equivalent to the J 42907  .
8. Run the engine and measure the engine oil pressure.
9. Compare the readings to Engine Mechanical Specifications .
10. If the engine oil pressure is below specifications, inspect the engine for one or more of the following:
    • Oil pump worn or dirty

      Refer to Oil Pump Cleaning and Inspection .

    • Oil pump screen loose, plugged, or damaged
    • Oil pump screen O-ring seal missing or damaged
    • Malfunctioning oil pump pressure regulator valve
    • Excessive bearing clearance
    • Cracked, porous, or restricted oil galleries
    • Oil gallery plugs missing or incorrectly installed

      Refer to Engine Block Plug Installation .

    • Broken valve lash adjusters

      Repair as necessary

11. If the reading on J 21867  or equivalent is within specifications, inspect for the following:
    • Plugged or incorrect oil filter and/or malfunctioning oil bypass valve
    • Malfunctioning vehicle oil pressure gage or sensor

      Repair as necessary