Oil Pressure Diagnosis and Testing

Tools Required

• EN-47971  Oil Pressure Gage Adapter. See Special Tools .
• J 21867  Pressure Gage

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: Oil Filter
Courtesy of GENERAL MOTORS CORP.
6. Remove the oil filter.
Fig 2: Oil Filter Adapter
Courtesy of GENERAL MOTORS CORP.
NOTE: 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.
7. Install the EN-47971  onto the oil filter adapter. See Special Tools .
Fig 3: NPT Fitting
Courtesy of GENERAL MOTORS CORP.
8. Install the 1/8 NPT fitting from the J 21867  into the port on the EN-47971  . See Special Tools .
Fig 4: Flexible Hose
Courtesy of GENERAL MOTORS CORP.
9. Install the J 21867  flexible hose to the EN-47971  . See Special Tools .
10. Run the engine and measure the engine oil pressure.
11. Compare the readings to Engine Mechanical Specifications .
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 and Oil Pump Pipe and Screen Cleaning and Inspection .
    • Oil pump screen O-ring seal missing or damaged. Refer to Oil Pump Suction Pipe and Screen Assembly Replacement and Oil Pump Pipe and Screen Cleaning and Inspection .
    • Oil pump pressure relief valve malfunction. Refer to Oil Pump Replacement .
    • Oil outlet tube bolts loose or missing, O-rings damaged or missing, mounting flange damaged and/or tube broken or damaged. Refer to Oil Pump Outlet Tube Removal , Oil Pump Outlet Tube Cleaning and Inspection and Oil Pump Outlet Tube Installation .
    • 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 - 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 .
    • Oil cooler lines or oil cooler heat exchanger leaking. Refer to Engine Oil Cooler Hose/Pipe Replacement , Engine Oil Cooler Pipe/Hose Quick Connect Fitting and Engine Oil and Transmission Fluid Cooler Replacement .
    • Crankshaft balancer bolt missing, loose or under-torqued.
    • Friction washer missing between any of the following:
      • Crankshaft balancer and the oil pump
      • Oil pump and the crankshaft sprocket
      • Crankshaft sprocket and crankshaft
NOTE: 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 J 21867  , 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 .
    • Malfunctioning oil pressure gage or sensor. Repair, as necessary. Refer to Engine Oil Pressure Sensor and/or Switch Replacement .