Oil Pressure Diagnosis and Testing

Tools Required

• J 21867  Pressure Gage. See Special Tools .
• J 42907  Oil Pressure Tester. See Special Tools .

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 the 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 conditions:
   • Oil diluted by water or glycol antifreeze
   • Foamy oil
Fig 1: View Of Oil Filter
Courtesy of GENERAL MOTORS CORP.
6. Remove the oil filter.
Fig 2: View Of J 42907 Oil Pressure Tester
Courtesy of GENERAL MOTORS CORP.
7. Install the J 42907  onto the oil filter adapter. See Special Tools .
Fig 3: Identifying 1/8 NPT Fitting
Courtesy of GENERAL MOTORS CORP.
8. Install the 1/8 NPT fitting from the J 21867  into the port on the J 42907  . See Special Tools .
Fig 4: View Of Flexible Hose
Courtesy of GENERAL MOTORS CORP.
9. Install the J 21867  flexible hose to the J 42907  . See Special Tools .
10. Run the engine and measure the engine oil pressure.
11. Compare the readings to Engine Mechanical Specifications (LD8)  or Engine Mechanical Specifications (L37) .
12. If the engine oil pressure is below specifications, inspect the engine for 1 or more of the following conditions:
    • Oil pump worn or dirty. Refer to Oil Pump Replacement , Oil Pump Disassemble and Oil Pump Cleaning and Inspection .
    • Oil pump-to-engine block bolts loose. Refer to Oil Pump Replacement .
    • Oil pump screen loose, plugged, or damaged. Refer to Oil Pump Suction Pipe and Screen Assembly Replacement .
    • Oil pump screen O-ring seal missing or damaged. Refer to Oil Pump Suction Pipe and Screen Assembly Replacement .
    • Oil pump pressure relief valve malfunction. Refer to Oil Pump Replacement .
    • Engine bearing clearance excessive. Refer to Crankshaft and Bearings Cleaning and Inspection , Crankshaft and Bearings Installation and Piston, Connecting Rod, and Bearing Installation .
    • Cracked, porous, or restricted oil galleries.
    • Oil gallery plugs missing or incorrectly installed. Refer to Engine Block Assemble - Upper and Cylinder Head Assemble .
    • Valve lifters broken. Repair, as necessary. Refer to Valve Lifter Replacement - Left Side and/or Valve Lifter Replacement - Right Side and Valve Lifters Cleaning and Inspection .
    • Crankshaft balancer bolt missing, loose or under-torqued.
13. If the oil pressure reading on the J 21867  , or equivalent, is within specifications, inspect for the following conditions:. See Special Tools .
    • Plugged or incorrect oil filter and/or malfunctioning oil bypass valve. Refer to Engine Oil and Oil Filter Replacement .
    • Malfunctioning oil pressure gage or sensor. Repair, as necessary. Refer to Engine Oil Pressure Sensor and/or Switch Replacement .