MBE 900

Section 15.8 Excessive Crankcase Pressure

Section 15.8
Excessive Crankcase Pressure

There are several causes for excessive crankcase pressure. These probable causes are:‪

  • Obstruction or Damage to Cylinder Head Cover Breather
  • Defective Air Compressor
  • Defective Turbocharger
  • Worn or Damaged Valve or Cylinder Kit

Section 15.8.1
Troubleshooting Procedure for Obstruction or Damage to Cylinder Head Cover Breather

To determine if an obstructed or damaged breather is causing excessive crankcase pressure, perform a crankcase pressure test. Refer to "15.4.10.1 Crankcase Pressure Test" .‪

  1. If the engine crankcase pressure is greater than 0.62 kPa (2.5 in. H2 O), replace wire mesh element; refer to "15.8.2 Cylinder Head Cover Breather Resolution" .
  2. If the crankcase pressure remained the same, check the air compressor; refer to "15.8.3 Troubleshooting Procedure for Defective Air Compressor" .

Section 15.8.2
Cylinder Head Cover Breather Resolution

Perform the following steps to replace wire mesh element:‪

  1. Remove the cylinder head cover; refer to "1.1.1 Cylinder Head Cover Removal" .
  2. Remove the wire mesh element from the cylinder head cover.
  3. Install a new wire mesh element to the cylinder head cover.
  4. Install the cylinder head cover to the engine; refer to "1.1.2 Cylinder Head Cover Installation" .
  5. Verify replacement of the wire mesh element; refer to "15.8.2.1 Test Engine with New Wire Mesh Element" .
Section 15.8.2.1
Test Engine with New Wire Mesh Element

Perform the following steps to determine if the new wire mesh element resolved the excessive crankcase pressure:‪

warning

PERSONAL INJURY

To avoid injury before starting and running the engine, ensure the vehicle is parked on a level surface, parking brake is set, and the wheels are blocked.

  1. Start and run the engine.
  2. Perform a crankcase pressure test; refer to "15.4.10.1 Crankcase Pressure Test" .
    1. If the engine crankcase pressure is less than 0.62 kPa (2.5 in. H2 O), no further troubleshooting is required. Shut down the engine.
    2. If the engine crankcase pressure is greater than 0.62 kPa (2.5 in. H2 O), check the air compressor; refer to "15.8.3 Troubleshooting Procedure for Defective Air Compressor" . Shut down the engine.

Section 15.8.3
Troubleshooting Procedure for Defective Air Compressor

To determine if a defective air compressor is causing excessive crankcase pressure, perform the following:‪

  1. Perform a crankcase pressure test and record the test results. Refer to "15.4.10.1 Crankcase Pressure Test" .
  2. Disconnect the air discharge line from the air compressor; see Figure "Air Line Attachments" . Refer to "10.1.1 Air Compressor Removal" .
    Click to see this graphic in a separate window

     1. Discharge Port‪

     4. Unloader Port‪

     2. Unloader Air Line‪

     5. Discharge Air Line‪

     3. Intake Air Line‪

     6. Air Compressor‪

    Figure 1. Air Line Attachments

  3. Repeat step 1 and record the test results.
  4. Compare the results of test one with test two.
    1. If the engine crankcase pressure remained the same, check the turbocharger; refer to "15.8.4 Troubleshooting Procedure for a Defective Turbocharger" .
    2. If the engine crankcase pressure decreased, repair or replace the air compressor; refer to "10.1 Air Compressor" .
Section 15.8.3.1
Test Engine with Repaired Air Compressor

Perform the following steps to determine if a repaired air compressor resolved the excessive crankcase pressure:‪

warning

PERSONAL INJURY

To avoid injury before starting and running the engine, ensure the vehicle is parked on a level surface, parking brake is set, and the wheels are blocked.

  1. Start and run the engine.
  2. Perform a crankcase pressure test; refer to "15.4.10.1 Crankcase Pressure Test" .
    1. If the engine crankcase pressure is within 0.62 kPa (2.5 in. H2 O), no further troubleshooting is required. Shut down the engine.
    2. If the engine crankcase pressure is not within 0.62 kPa (2.5 in. H2 O), shut down the engine. Check the turbocharger; refer to "15.8.4 Troubleshooting Procedure for a Defective Turbocharger" .

Section 15.8.4
Troubleshooting Procedure for a Defective Turbocharger

To determine if a defective turbocharger is causing excessive crankcase pressure, perform the following:‪

NOTICE:

Ensure that the engine is not allowed to operate longer than necessary to perform the crankcase pressure test. A complete loss of crankcase oil will severely damage the engine.‪

  1. Remove the turbocharger drain line connected to the crankcase and place the drain line into a suitable container; refer to "6.4.2 Turbocharger Removal" .
  2. Perform a crankcase pressure test; refer to "15.4.10.1 Crankcase Pressure Test" .
    1. If the engine crankcase pressure is less than 0.62 kPa (2.5 in. H2 O), replace the turbocharger; refer to "6.4.2 Turbocharger Removal" . Shut down the engine.
    2. If the engine crankcase pressure indicates no change, check for a worn or damaged valve or cylinder kit; refer to "15.8.6 Troubleshooting Procedure for Worn or Damaged Valve or Cylinder Kit" . Shut down the engine.

Section 15.8.5
Turbocharger Replacement

Perform the following steps to replace a defective turbocharger:‪

  1. Remove the defective turbocharger from the engine; refer to "6.4.2 Turbocharger Removal" .
  2. Tag the removed turbocharger for remanufacture.
  3. Install a replacement turbocharger to the engine; refer to "6.4.3 Turbocharger Installation" .
  4. Verify replacement of new turbocharger; refer to "15.8.5.1 Test Engine with New Turbocharger" .
Section 15.8.5.1
Test Engine with New Turbocharger

To determine if a new turbocharger resolved the excessive crankcase pressure, perform a crankcase pressure test. Refer to "15.4.10.1 Crankcase Pressure Test" .‪

  1. If the engine crankcase pressure is 0.62 kPa (2.5 in. H2 O) or less, no further troubleshooting is required. Shut down the engine.
  2. If the engine crankcase pressure is greater than 0.62 kPa (2.5 in. H 2 O), shut down the engine. Check for a worn or damaged valve or cylinder kit; refer to "15.8.6 Troubleshooting Procedure for Worn or Damaged Valve or Cylinder Kit" .

Section 15.8.6
Troubleshooting Procedure for Worn or Damaged Valve or Cylinder Kit

To determine if a worn or damaged cylinder kit is causing excessive crankcase pressure, perform the following:‪

  1. Move the vehicle requiring test to the chassis dynamometer; refer to OEM guidelines.
  2. Remove air compressor; refer to "10.1.1 Air Compressor Removal" .
    warning

    PERSONAL INJURY

    To avoid injury before starting and running the engine, ensure the vehicle is parked on a level surface, parking brake is set, and the wheels are blocked.

  3. Start the engine.
  4. Run the engine and bring the engine coolant temperature to normal operating range, approximately 88-96°C (190-205°F).
  5. Run the vehicle to full load and rated speed.
  6. Attach a manometer calibrated to read pressure kPa or inches of H2 O, to the oil dipstick opening.
  7. Measure and record crankcase pressure.
  8. Shut down the engine.
  9. Remove the vehicle from the chassis dynamometer.
  10. Review the crankcase pressure test.
    1. If the crankcase pressure is greater than 0.62 kPa (2.5 in. H 2 O), go to step 11 .
    2. If the crankcase pressure is less than 0.62 kPa (2.5 in. H 2 O), no further troubleshooting is required.
  11. Perform the cylinder compression test. Refer to "1.2.2.2 Compression Testing" .
    1. If cylinder pressure is below specifications, refer to Table "Compression Pressure Test Data" and refer to "15.8.7 Worn or Damaged Valve or Cylinder Kit Repair" .
    2. If cylinder pressure is within specifications, call Detroit Diesel Customer Support Center at 313-592-5800.

Section 15.8.7
Worn or Damaged Valve or Cylinder Kit Repair

Perform the following steps for a worn or damaged valve or cylinder kit:‪

  1. Remove the cylinder head; refer to "1.2.1 Cylinder Head Removal" .
  2. Inspect the cylinder head for worn or damaged valves; refer to "1.17 Valves" .
  3. Inspect the cylinder kit components for worn or damaged liners, piston or piston rings; refer to "1.15.3.1 Piston and Piston Ring Cleaning, Inspection, and Measuring" .
  4. Verify repair to cylinder valve(s) or cylinder kit components; refer to "15.8.7.1 Test Engine with Repairs Made to Correct Worn or Damaged Valve or Cylinder Kit" .
Section 15.8.7.1
Test Engine with Repairs Made to Correct Worn or Damaged Valve or Cylinder Kit

Perform the following to determine if the repaired valve or cylinder kit resolved the excessive crankcase pressure:‪

  1. Move the vehicle requiring test to the chassis dynamometer; refer to OEM guidelines.
  2. Disconnect air compressor; refer to "10.1.1 Air Compressor Removal" .
    warning

    PERSONAL INJURY

    To avoid injury before starting and running the engine, ensure the vehicle is parked on a level surface, parking brake is set, and the wheels are blocked.

  3. Start the engine.
  4. Run the engine and bring the engine coolant temperature to normal operating range, approximately 88-96°C (190-205°F).
  5. Run the vehicle to full load and rated speed.
  6. Attach a manometer calibrated to read pressure in kPa or inches of H2 O, to the oil dipstick opening.
  7. Measure and record crankcase pressure.
  8. Shut down the engine.
  9. Remove the vehicle from the chassis dynamometer.
  10. Compare the cylinder pressure test results to specifications listed in Table "Compression Pressure Test Data" .
    1. If cylinder pressure is within specifications, no further troubleshooting is required.
    2. If cylinder pressure is not within specifications, call Detroit Diesel Customer Support Center at 313-592-5800.


MBE 900 Service Manual - 6SE414
Generated on 10-13-2008

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