Skip to main content

MBE 900 LOW OIL PRESSURE

There are several causes for low oil pressure. These probable causes are: ‪

  • Improper Engine Oil Level
  • Improper Lubricating Oil Viscosity
  • Lubricating Oil Diluted with Fuel or Engine Coolant
  • Faulty Oil Pressure Gauge Sensor
  • Oil Pressure Gauge Line Obstructed
  • Restricted Oil Cooler
  • Defective Bypass Valve
  • Defective Pressure Relief Valve
  • Defective Pickup Screen Tube and Screen Assembly
  • Defective Crankshaft Main Bearing Shells
  • Defective Oil Pump Assembly

Troubleshooting Procedure for Improper Engine Oil Level

To determine if improper engine oil level is causing low oil pressure, perform the following steps: ‪

  1. Check the engine oil level. Listed in Table .

    Description ‪

    4Cylinder Engines ‪

    6Cylinder Engines ‪

    Oil Pan Capacity* ‪

    16 L (17 qt.) ‪

    29 L (31 qt.) ‪

    Lubricating Oil Capacity

    1. If the engine oil level is correct, check lubricating oil viscosity; refer to section .
    2. If the engine oil level is incorrect, refer to section .

Low Engine Oil Level Resolution

Perform the following steps for low engine oil level: ‪

  1. Fill engine oil pan to correct level listed in Table .
  2. Verify low engine oil resolution; refer to section .
Test for Proper Engine Oil Level

Perform the following steps to determine if properly filled oil pan has resolved low oil pressure: ‪

  1. Start and vary engine speed between 1800 - 2100 rpm.
  2. Stop the engine and measure oil pressure.
    1. If the oil pressure is correct, no further troubleshooting is required. Shut down the engine.
    2. If the oil pressure at rated speed is less than 250 kPa (36 psi), shut down the engine. Check lubricating oil viscosity; refer to section .

Troubleshooting Procedure for Improper Lubricating Oil Viscosity

To determine if improper lubricating oil viscosity is causing low oil pressure, perform the following steps: ‪

  1. Acquire a lubricating oil sample from the engine oil pan.
  2. Submit oil sample for an ASTMtest analysis.
    1. If engine oil sample meets ASTM specifications, check to determine if lubricating oil is diluted with fuel or coolant; refer to section .
    2. If engine oil sample did not meet ASTM specifications, refer to section .

Lubricating Oil Replacement

Perform the following steps to replace engine oil: ‪

  1. Drain and refill engine with new lubricating oil listed in Table .
  2. Verify lubricating oil replacement; refer to section .
Test Engine with Replaced Lubricating Oil

Perform the following steps to determine if replaced lubricating oil resolved low oil pressure: ‪

  1. Start and run engine speed at 1800 rpm.
  2. Stop the engine and measure oil pressure.
    1. If the oil pressure is correct, no further troubleshooting is required. Shut down the engine.
    2. If the oil pressure at rated speed is less than 250 kPa (36 psi), shut down the engine. Check the lubricating oil for fuel and engine coolant dilution; refer to section .

Troubleshooting Procedure for Lubricating Oil Diluted with Fuel or Engine Coolant

To determine if lubricating oil diluted with fuel or engine coolant, is causing low oil pressure, perform the following steps: ‪

  1. Acquire a lubricating oil sample from the engine oil pan.
  2. Visually examine lubricating oil sample for presence of engine coolant or fuel.
    1. If coolant or fuel are not present, check for a faulty oil pressure gauge; refer to section .
    2. If coolant or fuel are present, refer to section .

Contaminated Lubricating Oil Resolution

Perform the following steps to resolve contaminated lubricating oil: ‪

  1. If coolant is present, consider head gasket replacement and repair as required.
  2. If fuel is present, consider fuel nozzle replacement and repair as required.
  3. Drain engine oil pan.
  4. Refill engine crankcase with new oil.
  5. Verify lubricating oil replacement; refer to section .
Test Replaced Lubricating Oil

Perform the following steps to determine if replaced lubricating oil resolved low oil pressure: ‪

  1. Start and run the engine speed at 1800 rpm.
    1. If the oil pressure is correct, no further troubleshooting is required.
    2. If the oil pressure at rated speed is less than 250 kPa (36 psi), shut down the engine. Check for faulty oil pressure gauge; refer to section .

Troubleshooting Procedure for Faulty Oil Pressure Gauge Sensor

To determine if a faulty oil pressure gauge sensor is causing low oil pressure, perform the following steps: ‪

  1. Install the Diagnostic Data Reader.
  2. Start and vary the engine speed between 18002100 rpm.
  3. Visually examine the DDR for oil pressure reading.
    1. If the oil pressure is greater than or equal to 250 kPa (36 psi) at 1800 rpm., shut down the engine.
    2. If the oil pressure is less than 250 kPa (36 psi) at 1800 rpm., shut down the engine; refer to section .

Oil Pressure Gauge Sensor Replacement

Perform the following steps to replace the oil pressure gauge sensor: ‪

  1. Remove and replace the oil pressure gauge sensor; refer to OEMguidelines.

Troubleshooting Procedure for Oil Pressure Gauge Line Obstructed

To determine if an oil pressure gauge line obstruction is causing low oil pressure, perform the following steps: ‪

  1. Disconnect oil gauge line from oil pressure gauge; refer to OEMguidelines.
  2. Visually inspect oil gauge line for obstructions.
    1. If no obstructions are found; check to determine if rocker arm shaft plugs are missing (new or rebuilt engines only).
    2. If obstructions are found, refer to section .

Obstructed Oil Pressure Gauge Line Repair

Perform the following steps to resolve oil pressure gauge line obstructions. ‪

  1. Remove oil pressure gauge line; refer to OEMguidelines.
  2. Clean oil gauge line by soaking in cleaning solution for five minutes.
  3. Blow out oil gauge line of residue contamination with compressed air.
  4. Install cleaned oil gauge line; refer to OEMguidelines.
  5. Verify oil gauge line repair; refer to section .
Test the Engine with Repaired Oil Gauge Line

Perform the following steps to determine if replaced oil pressure gauge resolved low oil pressure: ‪

  1. Start and run engine speed at 1800 rpm.
    1. If the oil pressure is correct, no further troubleshooting in required. Shut down the engine.
    2. If the oil pressure at rated speed is less than 250 kPa (36 psi), shut down the engine. Check for restricted oil cooler; refer to section .

Troubleshooting Procedure for Restricted Oil Cooler

To determine if a restricted oil cooler is causing low oil pressure, perform the following steps: Refer to section for the two emission cautions. ‪

  1. Start and run the engine at 1800 rpm.
  2. Run the engine at 1800 rpm. with a no-load condition for approximately five minutes, allowing the engine coolant to reach normal operating range 88 - 96C (190 - 205F).
    1. If the oil temp. sensor is indicating a lubricating oil temperature less than or equal to 110C (230F), shut down the engine and check for a defective bypass valve; refer to section .
    2. If the oil temp. sensor is indicating a lubricating oil temperature greater than 110C (230F), shut down the engine and repair oil cooler; refer to section .

Oil Cooler Repair

Perform the following steps to repair the oil cooler: ‪

  1. Remove the oil cooler.
  2. Clean the oil cooler before sludge hardens. Flush oil passages with clean, hot water.
  3. Inspect the oil cooler for damage.
  4. Install repaired oil cooler.
  5. Verify repair of oil cooler; refer to section .
Test Engine with Repaired Oil Cooler

Perform the following steps to determine if oil cooler repair resolved low oil pressure: ‪

  1. Start and run the engine 1800 rpm.
  2. Run the engine through its operating range with no-load condition for approximately five minutes, allowing the engine coolant to reach normal operating range, 88 - 96C (190 - 205F).
    1. If the DDR indicates 241 kPa (35 psi) or more at 1800 rpm, shut down the engine and disconnect the DDR. No further troubleshooting is required.
    2. If the DDR indicates less than 241 kPa (35 psi) or more at 1800 rpm, shut down the engine and disconnect the DDR. Check for defective bypass valve; refer to section .

Troubleshooting Procedure for Defective Bypass Valve

To determine if a defective bypass valve is causing low oil pressure, perform the following steps: ‪

  1. Remove the oil pressure/temperature sensor.
  2. Inspect the oil filter bypass valve components.
    1. If no damage is found with the oil filter housing bypass valve components, check for defective pressure relief valve; refer to section .
    2. If damage is found with the oil filter housing bypass valve bore, replace housing.

Troubleshooting Procedure for Defective Pressure Relief Valve

To determine if a defective pressure relief valve is causing low oil pressure, perform the following steps: ‪

  1. Remove the pressure relief valve.
  2. Inspect the oil pressure relief valve.
    1. If the relief valve moves freely in the valve body, reinstall the oil pressure relief valve. Check the pickup tube and screen assembly for defects; .
    2. If the relief valve will not move freely in the valve body, refer to section .

Pressure Relief Valve Repair

Perform the following steps to repair the pressure relief valve: ‪

  1. Disassemble the pressure relief valve and replace damaged components.
  2. Assemble and install the pressure relief valve.
  3. Verify repair of the relief valve; refer to section .
Test Engine with Repaired Relief Valve

Perform the following steps to determine if repaired relief valve resolved low oil pressure: ‪

  1. Install the Diagnostic Data Reader.
  2. Start and run engine speed at 1800 rpm.
  3. Visually examine the DDR for oil pressure reading.
    1. If the DDR indicates 241 kPa (35 psi) or more at 1800 rpm., shut down the engine and disconnect the DDR. No further troubleshooting is required.
    2. If the DDR indicates less than 241 kPa (35 psi) at 1800 rpm, shut down the engine and disconnect the DDR. Check for defective pickup tube and screen assembly; refer to section .

Troubleshooting Procedure for Defective Pickup Screen Tube and Screen Assembly

To determine if a defective pickup screen tube or screen assembly is causing low oil pressure, perform the following steps: ‪

  1. Remove pickup screen tube and screen assembly.
  2. Visually inspect pickup screen tube and screen assembly.
    1. If no tube stress cracks, twisted screen tube, or cracked flange gaskets are found, check for defective crankshaft main bearing shells; refer to section .
    2. If stress cracks, twisted screen tube, or cracked flange gaskets are found, refer to section .

Pickup Screen Tube and Screen Assembly Repair

Perform the following steps to repair the pickup screen tube and screen assembly: ‪

  1. Replace all damaged components identified during inspection and install.
  2. Verify repairs to pickup screen tube and screen assembly; refer to section .
Test Engine with Repaired Pickup Screen Tube and Screen Assembly

Perform the following steps to determine if repaired relief valve resolved low oil pressure: ‪

  1. Start and run the engine speed at 1800 rpm.
  2. Visually examine oil pressure reading.
    1. If the oil pressure is correct, no further troubleshooting is required.
    2. If the oil pressure at rated speed is less than 250 kPa (36 psi), check for defective crankshaft main bearing shells; refer to section .

Troubleshooting Procedure for Defective Crankshaft Main Bearing Shells

To determine if defective crankshaft main bearing shells are causing low oil pressure, perform the following steps: ‪

  1. Check main bearing to crankshaft journal clearances; .
    1. If main bearing shell-to-journal clearance is within 0.051-0.127 mm (0.002-0.005 in.), check for defective oil pump assembly; refer to section .
    2. If main bearing shell-to-journal clearance is not within 0.051-0.127 mm (0.002-0.005 in.), refer to section .

Crankshaft Main Bearing Shell Repair

Perform the following steps to repair crankshaft main bearing shells: ‪

  1. Remove and replace defective crankshaft main bearing shells.
  2. Verify crankshaft main bearing shells repair; refer to section .
Test Engine with New Crankshaft Main Bearing Shells

Perform the following steps to determine if new crankshaft main bearing shells have resolved low oil pressure: ‪

  1. Start and run engine speed to 1800 rpm.
  2. Visually examine the oil pressure reading.
    1. If the oil pressure is correct, no further troubleshooting is required. Shut down the engine.
    2. If the oil pressure at rated speed is less than 250 kPa (36 psi), shut down the engine. Check the oil pump assembly; refer to section .

Troubleshooting Procedure for Defective Oil Pump Assembly

To determine if a defective oil pump is causing low oil pressure, perform the following steps: ‪

  1. Remove the oil pump assembly; refer to section .
  2. Manually rotate the oil pump drive gear.
    1. If the drive gear rotates freely in the pump housing, call Detroit Diesel Technical Service Group.
    2. If the drive gear did not rotate freely, replace the oil pump assembly and verify repair; refer to section .
Test Engine with Replaced Oil Pump Assembly

Perform the following steps to determine if oil pump replacement resolved low oil pressure: ‪

  1. Start and run the engine speed at 1800 rpm.
  2. Visually examine the oil pressure reading.
    1. If the oil pressure is correct, no further troubleshooting is required. Shut down the engine.
    2. If the oil pressure at rated speed is less than 250 kPa (36 psi), shut down the engine and call Detroit Diesel Technical Service Group.