PRODUCT SUPPORT PROGRAM FOR INSPECTING THE CAMSHAFT ON CERTAIN 793F OFF-HIGHWAY TRUCKS
AVSpare’s obligations under this Service Letter are subject to, and shall not apply in contravention of, the laws, rules, regulations, directives, ordinances, orders, or statutes of the United States, or of any other applicable jurisdiction, without recourse or liability with respect to AVSpare.
This Program must be administered either before or after failure. In either case the decision whether to apply the Program is made by the dealer. When reporting the repair, use "PS46540" as the Part Number and "7755" as the Group Number. If administered before failure, use "56" as the Warranty Claim Description Code and "T" as the SIMS Description code. If administered after failure, use "96" as the Warranty Claim Description Code, and "Z" as the SIMS Description Code.
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 AVSpare product analyst.
This Revised Service Letter replaces the 02Jan2020 (Revised 07Feb2020) Service Letter. Changes have been made to the Rework Procedure.
|The existing camshaft can fail on certain 793F Off-Highway Trucks. If the existing camshaft fails it will cause unplanned downtime.|
|793F||SSP00460-00461, 468, 487-488, 799-800, 829, 837, 840, 857, 865, 876, 879-880, 989, 993, 1033, 1041-1042, 1044-1045, 1048, 1073-1074, 1196, 1208, 1210-1212, 1214-1219|
|793F CMD||RBT00222, 224-226, 228-229, 231-236|
|In order to allow equitable parts availability to all participating dealers, please limit your initial parts order to not exceed 32% of dealership population. This is an initial order recommendation only, and the ultimate responsibility for ordering the total number of parts needed to satisfy the program lies with the dealer.
|Utilize a high quality borescope to inspect the nose and down ramp of each camshaft lobe for damage.
Flexible borescope with a 4mm diameter lead that can be manipulated 6mm(1/4 inch) diameter thin wall guide tube 558 mm (22 inches) long.
Engine turning tool (329-3831)
See Image 1 below for an example of an acceptable borescope.
This service letter may be claimed multiple times. It is recommended to begin performing borescope inspections at 2,000 engine hours, repeating every 2,000 hours up to 18,000 hours. For engines that are exhibiting initial signs of failure, the inspection interval should be reduced to 1,000 hours.
Refer to the attached Rework Procedure for the inspection procedure for
the proper method to inspect the camshaft lobes.
Please attach a report with photos from each inspection along with the
recommended actions to the SIMSi entry.
SERVICE CLAIM ALLOWANCES
| NOTE: This is a 10.0-hour job
If there has been a previous repair, part age/hours will apply. Retain a copy of the previous repair invoice in the dealer's records for audit purposes, and specify repair date and machine hours in the "Additional Comments" section of the warranty claim.
|Handle the parts in accordance with your Warranty Bulletin on warranty parts handling.|
|Refer to Image1.1.1 to identify the area to be inspected and the orientation of each camshaft lobe.|
|1. Remove LEFT side valve covers ONLY (viewed from flywheel end).
2. Rotate the engine Counter Clockwise until the flywheel timing pin can be installed.
3. Using the Test and Adjust guide (KENR5397), make sure that the #1 piston is on the COMPRESSION stroke.
4. Remove and store crankshaft timing pin.
5. If borescope is equipped with a moveable handle, place it on the borescope lead.
6. Feed borescope lead through the guide tube until it protrudes at
7. Move handle down until it touches the top of guide tube and secure to borescope lead.
8. Using joy stick, move borescope end to ensure that movement is not restricted by the tube.
9. Pull borescope lead part way out of guide tube (far enough that the camera is not protruding out of the guide tube.
10. Holding borescope lead and guide tube, insert guide tube above the rocker arms and under the push rod opening. See Image1.2.1 below.
|11. Column one of Image1.3.1 shows what cam lobes can be inspected for a C175-16 starting with the flywheel on Top Center #1 Compression. Left and right refer to the push rods and our recommendation of which hole to probe for clearest view of the cam lobe.
12. After completing the first column, rotate the flywheel 90 degrees counter clockwise and inspect the lobes listed in column 2. Mark the damper to determine when 90 degrees has been reached.
13. Repeat inspections every 90 degrees until the crankshaft has been rotated 2 complete turns and all intake and exhaust lobes have been inspected. The tables in Image1.3.1 need to be completed for a C175-16 engine.
|14. Use Image1.4.1, Image1.4.2, and Image1.4.3 to evaluate the condition of the camshaft lobes and determine the recommended actions.
Camshaft lobes that match ImageI.4.1 are in acceptable condition and should be re-inspected in 2,000 hours. Fine debris scratches and minor indentations may be apparent and are acceptable.
Camshaft lobes that match Image1.4.2 show the signs of roller skidding and will progress to a spalled lobe. A repair should be scheduled as soon as possible. There will be a defined track(s) with disturbed material causing a rough finish and a visual contrast in roller path.
Camshaft lobes that match Image 1.4.3 are failed and need replaced immediately.