ISC, ISCe, QSC8.3, ISL, ISLe3, ISLe4 and QSL9 Engines – Engine Noise Excessive — Main Bearing

Symptom Tree  t050

This is symptom tree t050
Cause Correction

Refer to Engine Noise Diagnostic Procedures – General Information at the end of Section TS before using this symptom tree.

Lubricating oil pressure is below specification

Check the oil pressure. If the pressure is low, refer to Procedure 007-037.


Lubricating oil level is below specification

Check the oil level. Verify the dipstick calibration and the oil pan capacity. Fill the system to the specified level. Refer to Procedures 007-037 and 007-009.


Lubricating oil is thin or diluted

Refer to Procedure 007-083. If the oil pressure is low, refer to the Lubricating Oil Pressure Low symptom tree.


Main bearing capscrews are loose, worn or not tightened correctly

Check the torque on the main bearing capscrews. Inspect the capscrews for wear. Refer to Procedure 001-006.


Main bearings are damaged or worn, or the wrong bearings are installed

Inspect the main bearings for damage, excessive wear, and the correct part number. Refer to Procedure 001-006.


Crankshaft journals are damaged or out of round

Inspect the crankshaft journals. Refer to Procedure 001-016.


Flywheel or flexplate capscrews are loose or broken

Check the flywheel or flexplate and the mounting capscrews. Refer to Procedure 016-005.

Last Modified:  29-Jul-2005