A New Exhaust Coupling With A Flow Conditioner Feature Needs To Be Installed On Certain 793C Trucks Caterpillar

August 18, 1998
U-231
A-213
AU-178
S-106
O-204

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 must be administered as soon as possible. When reporting the repair, use "PI3158" as the Part Number, "7751" as the Group Number, "56" as the Warranty Claim Description Code and "T" as the SIMS Description Code. Exception: If the repair is done after failure, use "PI3158" as the Part Number, "7751" as the Group Number, "96" as the Warranty Claim Description Code, and "Z" as the SIMS Description Code.

NOTE: Refer to your Warranty Bulletin for detailed information with regard to Product Improvement Programs.

Completion Date

Termination Date

Problem

Exhaust swirl between the 793C high pressure turbine outlet and the low pressure turbine inlet can cause high stress in the low pressure turbine blades. A new coupling with a flow conditioner feature will reduce the exhaust swirl and lower the stress in the low pressure turbine blades. The lower stress will increase the service life of the low pressure turbo.

Affected Product
Model & Identification Number

793C (4AR1-355, 4AR357-369, 4AR377-381, 4AR384)

Spare/Reman Engines

3516B (7TR17TR-Up7TR583)

3516B ( REMAN7DS17DS-Up7DS149)

Parts Needed

12 - 5P7128 Bolt-Washer

2 - 1586601 Coupling

Action Required

See the attached procedure.

Owner Notification

U.S. and Canadian owners will receive the attached Owner Notification.

Service Claim Allowances

NOTE: Labor may be claimed if the repairs are made in chassis.Labor may also be claimed on a spare or reman engine in dealer stock.Labor may not be claimed if the update is installed during an overhaul.

NOTE: Use a 99Z code for spare components in the serial number field when claiming against a spare engine.

NOTE: 4 hours may be claimed for every turbine housing that must be removed, salvaged, and installed due to broken bolts.

Parts Disposition

Handle the parts in accordance with your Warranty Bulletin on warranty parts handling.

NOTE: MAKE EVERY EFFORT TO COMPLETE THIS PROGRAM AS SOON AS POSSIBLE.

Attach.

(1-Owner Notification)

(2-Rework Procedure)

Copy Of Owner Notification For U.s. And Canadian Owners

Rework Procedure

1. Remove the front and rear turbo steps.

2. Remove the two 1215809 Exhaust Couplings. See Illustration 1 and the steps below.

3. Generously use penetrating oil on the six inch 5P7128 bolts that connect the exhaust coupling to the high pressure turbine outlet. Carefully and slowly remove the six bolts.

4. If a bolt breaks off in the turbine housing, salvage the housing by drilling out the broken bolt. Extra labor is allowed to remove, salvage, and re-install the turbine housing.

5. Carefully remove the four inch 9X8285 Bolts at the low pressure turbine inlet. This hardware will be reused.

6. Remove the old 1215809 Exhaust Coupling and install a new 1586601 Exhaust Coupling with the flow conditioner feature. Position the flow conditioner with the "up" arrow pointing up.

7. Install six new inch 5P7128 Bolts with antiseize compound on the bolt threads and bearing surfaces. Tighten the six bolts to 47 ± 5 Nm.

8. Install the four previously removed inch hardware with antiseize compound on the bolt threads and bearing surfaces. Tighten the four bolts to 215 ± 40 Nm.

9. Re-tighten the inch bolts to 215 ± 40 Nm and re-tighten the inch bolts to 47 ± 5 Nm.

10. Repeat the process for both the front and rear low pressure turbos.

11. Install the front and rear turbo steps.

12. Start the engine and check for proper operation.