Usage:
NOTE: The information supplied in this service letter may not be valid after the termination date of this program. Do not perform the work outlined in this Service Letter after the termination date without first contacting your Caterpillar product analyst.
NOTE: This Program can only be administered after a failure occurs. The decision whether to apply the Program is made by the dealer. When reporting the repair, use "PS5261" as the Part Number and "7755" as the Group Number. Use "96" as the Warranty Claim Description Code and use "Z" as the SIMS Description Code.
NOTE: This Revised Service Letter replaces the July 20, 1997 (Revised August 1998) Service Letter. Changes have been made to the Action Required.
Termination Date
July 31, 1999Problem
The turbine wheel or compressor wheel in the 4P4646, 1141980/">1141980, or 1220351 Low Pressure Turbocharger in certain 793 or 793B Trucks, or the 1234874 or 1480833 Low Pressure Turbocharger in certain 793C Trucks may fail .
Affected Product
Model & Identification Number
793 (3SJ1-56)
793B (1HL1-524)
793C (4AR1-99999)
Parts Needed
- 2 - 6D9157 Seal-O-Ring
- 2 - 6L1694 Gasket
- 4 - 5P8940 Seal-O-Ring
- 4 - 5P9757 Seal-O-Ring
- **1 - 0R6974 Turbo Group (For 793 and 793B)
- 1 - 0R6975 Cartridge Group (For Parts Stock action only)
- 8 - 9S8752 Nut
- 8 - 9S8752 Nut
- 2 - 6V4589 Seal-O-Ring
- 2 - 617539 Seal-O-Ring
- **1 - 1234874 Turbo Group (For 793C 8000-up feet altitude)
- **1 - 1480833 Turbo Group (For 793C 0-9000 feet altitude)
- *2 - 1596076 Turbine Coupling
- *2 - 1586601 Turbine Coupling
- 2 - 6L1694 Gasket
*Use two 1596076 turbine couplings on 793 and 793B engines only. Use two 1586601 turbine couplings on 793C engines only.
**Use 0R6974 Remanufactured Turbo to repair 793 or 793B Trucks. Use a 1480833 Turbo to repair 793C Trucks from zero to 9000 feet altitude. Use a 1234874 Turbo Group to repair a 793C Truck from 8000 feet and up.
Action Required
Parts Stock
Remove all 4P4646 and 1141980 Turbochargers and 4P6027, 1141981/">1141981, 0R6562, and 0R6824 Cartridges from Parts Stock.
Rework the 1141980 Turbochargers in Parts Stock. Replace the 1141981 Cartridge with an 0R6975 Reman Cartridge then return the turbocharger to Parts Stock as a 1220351 Turbocharger.
Affected Product
1. If the turbine wheel or compressor wheel fails in fatigue, remove the failed turbo.
2. Check the engine for failed high-pressure turbochargers, debris in the engine air intake or exhaust system. Clean out any debris.
3. Replace the failed turbo with a new or remanufactured turbo.
NOTE: If a 4P4646 Turbocharger fails, both Low Pressure Turbochargers must be replaced. If a 1141980 or 1220351 Turbocharger fails on a 793 or 793B Truck, or a 1234874 or 1480833 Turbocharger fails on a 793C Truck, only replace the failed low pressure turbocharger.
If the engine has mechanical unit injectors, make sure it has been updated to contain a 42 mm wastegate orifice plate, 1220562.
If the engine has electronic unit injectors, make sure it has been updated with a smart wastegate.
4. If the new 159-6076 or 158-6601 turbine couplings (flow conditioners) were not installed between the high pressure turbine outlet and the low pressure turbine inlet, install two turbine couplings during repairs to the failed turbo.
Service Claim Allowances
Parts Stock
Submit one claim for all 4P4646 Turbochargers and 4P6027, 1141981/">1141981, 0R6562, and 0R6824 Cartridges removed from Parts Stock.
Submit one claim for all 1141980 Turbochargers reworked to 1220351.
Affected Product
NOTE: Allow 6 hours labor for each turbo replaced in chassis.
Allow 3 hours labor and one 0R6975 Reman Cartridge for each 1141980 Turbocharger in Parts Stock that is reworked to a 1220351 Turbocharger.
Parts Disposition
Handle the parts in accordance with your Warranty Bulletin on warranty parts handling.