Oil Pressure Diagnosis and Testing

Special Tools

• EN-47971  Oil Pressure Gauge Adapter
• CH-48027  Pressure Gauge

For equivalent regional tools, refer to Special Tools (LF3)Special Tools (LGX) .

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 gauge 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

6. Courtesy of GENERAL MOTORS COMPANY

   Remove the oil filter.

7. Courtesy of GENERAL MOTORS COMPANY

   CAUTION:

   Special new tool EN 47971 must be used. Due to the special size and thread pitch of the oil filter adapter fitting ensure the proper tool is used or component damage will result.

   Install the EN-47971  adapter onto the oil filter adapter.

8. Courtesy of GENERAL MOTORS COMPANY

   Install the 1/8 NPT fitting from the CH-48027  gauge into the port on the EN-47971  adapter.

9. Courtesy of GENERAL MOTORS COMPANY

   Install the CH-48027  gauge flexible hose to the EN-47971  adapter.

10. Run the engine and measure the engine oil pressure.
11. Compare the readings to Engine Mechanical Specifications (LF3)Engine Mechanical Specifications (LGX) .
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 (LF3)Oil Pump Replacement (LGX) , Oil Pump Disassemble (LF3)Oil Pump Disassemble (LGX) , and Oil Pump Cleaning and Inspection (LF3)Oil Pump Cleaning and Inspection (LGX) .
    • Oil pump-to-engine block bolts loose. Refer to Oil Pump Replacement (LF3)Oil Pump Replacement (LGX) .
    • Oil pump screen loose, plugged, or damaged. Refer to Oil Pump Suction Pipe and Screen Assembly Replacement (LF3)Oil Pump Suction Pipe and Screen Assembly Replacement (LGX, AWD)Oil Pump Suction Pipe and Screen Assembly Replacement (LGX, RWD) , and Oil Pump Suction Pipe and Screen Cleaning and Inspection (LF3)Oil Pump Suction Pipe and Screen Cleaning and Inspection (LGX) .
    • Oil pump screen O-ring seal missing or damaged. Refer to Oil Pump Suction Pipe and Screen Assembly Replacement (LF3)Oil Pump Suction Pipe and Screen Assembly Replacement (LGX, AWD)Oil Pump Suction Pipe and Screen Assembly Replacement (LGX, RWD) , and Oil Pump Suction Pipe and Screen Cleaning and Inspection (LF3)Oil Pump Suction Pipe and Screen Cleaning and Inspection (LGX) .
    • Oil pump pressure relief valve malfunction. Refer to Oil Pump Replacement (LF3)Oil Pump Replacement (LGX) .
    • Engine bearing clearance excessive. Refer to Crankshaft and Bearing Cleaning and Inspection , Crankshaft and Bearing 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 (LF4)Engine Block Assemble (LGX) , and Cylinder Head Assemble (LF3)Cylinder Head Assemble (LGX) .
    • Valve lifters broken. Repair, as necessary. Refer to Valve Lifter Replacement - Left Side (LF3)Valve Lifter Replacement - Left Side (LGX) , and/or Valve Lifter Replacement - Right Side (LF3)Valve Lifter Replacement - Right Side (LGX) , and Valve Lifter Cleaning and Inspection (LF3)Valve Lifter Cleaning and Inspection (LGX) .
CAUTION:

This engine uses a special high performance oil filter. Use of any other filter may lead to filter failure and/or severe engine damage.

13. If the oil pressure reading on the CH-48027  gauge, or equivalent, is within specifications, inspect for the following conditions:
    • Plugged or incorrect oil filter and/or malfunctioning oil bypass valve. Refer to Engine Oil and Oil Filter Replacement (LF3)Engine Oil and Oil Filter Replacement (LGX, RWD)Engine Oil and Oil Filter Replacement (LGX, AWD) .
    • Malfunctioning oil pressure gauge or sensor. Repair, as necessary. Refer to Engine Oil Pressure Sensor and/or Switch Replacement (LF3)Engine Oil Pressure Sensor and/or Switch Replacement (LGX) .