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

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Symptom Tree  t047

This is symptom tree t047
Cause Correction

When troubleshooting engine noise complaints, make sure the engine accessories (air compressor, fan clutch, refrigerant compressor, or hydraulic pump) are not the cause of the noise. Refer to Engine Noise Diagnostic Procedures – General Information at the end of Section TS before using this symptom tree.

Electronic fault codes active or high counts of inactive fault codes

Read the fault codes with an electronic service tool. Refer to Section TF in Troubleshooting and Repair Manual, ISB, ISBe2, ISBe3, ISBe4, QSB4.5, QSB5.9, QSB6.7, ISC, QSC8.3, ISL and ISL, ISLe3, ISLe4, and QSL9, CM850 Electronic Control System, Bulletin
4021416 or Troubleshooting and Repair Manual, Electronic Control System, ISC, QSC8.3 and ISL Engines, Bulletin


Air intake or exhaust leaks

Inspect the air intake and exhaust systems for air leaks. Refer to Procedure 010-024 in Section 10.


Fan drive belt is loose

Check the belt tension and tighten if necessary. Refer to Procedure 008-002 in Section 8.


Fan is loose, damaged, or not balanced

Check the fan. Refer to Procedure 008-040 in Section 8.


Fan clutch, hydraulic pump, or refrigerant compressor noise is excessive

Isolate each component and check for noise. Refer to Procedure 008-040 in Section 8,
Procedure 009-016 in Section 9, or the OEM service manual.


Air intake or exhaust piping is contacting the chassis or cab

Inspect the air piping, chassis, and cab for contact points. Refer to the OEM service manual.


Lubricating oil level is above or below specification

Check the oil level. Add or drain oil, if necessary. Refer to Procedure 007-037 in Section 7.


Lubricating oil is thin or diluted

Refer to Procedure 007-083 in Section 7. If the oil pressure is low, refer to the Lubricating Oil Pressure Low symptom tree.


Lubricating oil pressure is below specification

Check the oil pressure. If the pressure is low,refer to Procedure 007-037 in Section 7.


Vibration damper is damaged

Inspect the vibration damper. Refer to Procedure 001-051 or
001-052 in Section 1.


Coolant temperature is above specification

Refer to the Coolant Temperature Above Normal – Gradual Overheat symptom tree.


Drivetrain noise is excessive

Disconnect the drivetrain. Check for engine noise. Refer to the OEM service manual.


Engine mounts are worn, damaged, or not correct

Check the engine mounts. Refer to Procedure 016-002 or
016-003 in Section 16.


Air compressor noise is excessive

Refer to the Air Compressor Noise Excessive symptom tree.


Overhead adjustments are not correct

Measure and adjust the overhead settings. Refer to Procedure 003-004 in Section 3.


Overhead components are damaged

Inspect the rocker levers, rocker shafts, and valves for damage or excessive wear. Refer to Procedure 003-008 in Section 3.


Injector is malfunctioning

Perform the single-cylinder cutout test. Replace the injectors as necessary. Refer to Procedure 006-026 in Section 6 or
Procedure 014-008 in Section 14.


Torque converter is loose

Check the torque converter. Refer to the OEM service manual.


Flywheel or flexplate capscrews are loose or broken

Check the flywheel or flexplate and the mounting capscrews. Refer to the OEM service manual.


Gear train backlash is excessive or the gear teeth are damaged

Check the gear backlash and the gear teeth. Refer to Procedure 001-008 in Section 1.


Main bearing or connecting rod bearing noise

Refer to the Engine Noise Excessive – Connecting Rod or the Engine Noise Excessive – Main Bearing symptom trees.


Turbocharger noise

Refer to the Engine Noise Excessive – Turbocharger symptom tree.


Combustion noise excessive

Refer to the Engine Noise Excessive – Combustion Knocks symptom tree.


Piston or piston rings are worn or damaged

Check for air intake system leaks. Check the pistons and piston rings for wear or damage. Refer to Procedure 010-024 in Section 10 or
Procedure 001-047 in Section 1.

Last Modified:  02-Nov-2009