PRODUCT SUPPORT PROGRAM FOR MEASURING AND RECORDING ENGINE VALVE RECESSION AND IF NECESSARY REPLACING CYLINDER HEADS WITH INTAKE VALVE RECESSION ON CERTAIN 794 AC, AND 795F AC OFF-HIGHWAY TRUCKS Caterpillar

PRODUCT SUPPORT PROGRAM FOR MEASURING AND RECORDING ENGINE VALVE RECESSION AND IF NECESSARY REPLACING CYLINDER HEADS WITH INTAKE VALVE RECESSION ON CERTAIN 794 AC, AND 795F AC OFF-HIGHWAY TRUCKS

Usage:

TEBE9007-00

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23May2019

U-301

A-248

D-263

O-267

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Before/After	PRODUCT SUPPORT PROGRAM FOR MEASURING AND RECORDING ENGINE VALVE RECESSION AND IF NECESSARY REPLACING CYLINDER HEADS WITH INTAKE VALVE RECESSION ON CERTAIN 794 AC, AND 795F AC OFF-HIGHWAY TRUCKS
1100		PS46273

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NOTE:

Caterpillar’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 Caterpillar.

NOTE:

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 "PS46273" 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.

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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.

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TERMINATION DATE

31May2021

PROBLEM

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The existing cylinder heads can experience intake valve recession on certain 794 AC, and 795F AC Off-Highway Trucks. If the existing cylinder heads experience intake valve recession it can result in a valvetrain failure.

Intake valve recession has been sporadic in nature with electric drive trucks showing a higher rate of occurrence. Typically, only a limited number of cylinder heads will show valve recession aggressive enough to require that the head be changed during the life of the engine. Some sites have proven to have more widespread intake valve recession than others, but the issue is very manageable when some simple measuring steps are employed.

AFFECTED PRODUCT

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Model	Identification Number
794 AC	HRT00100-00102 MN500052-00056 MT500100-00143
795F AC	ERM00151-00300
795F XQ	SNT00100-00105

PARTS NEEDED

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Qty	Part Number	Description
1	8C3132	SEAL-O RING
4	8T2223	BOLT-SOCKET HD
1	8T9524	SEAL-O-RING
1	20R7042	HEAD GP-CYL BSC
1	2287089	SEAL-O-RING-ORFS
1	2287100	SEAL-O-RING-STOR
1	2287108	SEAL-O-RING-STOR
1	2300940	SEAL
1	2435741	SEAL-FUEL SYSTEM
1	2435742	SEAL-FUEL SYSTEM
1	2464924	GASKET
1	2589925	GASKET-COMB
1	2589926	GASKET
1	2697852	SEAL-O-RING
1	3170808	SEAL-O-RING
1	3708028	SEAL-INTEGRAL
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.

ACTION REQUIRED

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Before Failure: Measure and record the engine valve recession.

Refer to the Service Manual if/as necessary.

Refer to Special Instruction ?M0081144? ?Procedure to Measure Valve Recession for C175 Engines?.

Refer to Testing and Adjusting ?KENR9188? ?C175-16 Engines for Off-Highway Truck/Tractors?, Valve Lash - Adjust.

Refer to the Channel1 video for C175 valve adjustment at the following link:
https://channel1.mediaspace.kaltura.com/media/1_654k8o0d

1.) Measure, record, and adjust valve lash. If previous records are not available, the Caterpillar Dealer will need to target C175 engines between 6000-8000 component hours to start establishing a baseline.

2.) Track lash measurements at each adjustment interval and monitor for valves that get tighter over time. If no previous valve stem projection measurements have been taken on engine and recorded, then each intake valve on that engine should be measured for valve recession to establish a baseline. All this data is to be recorded and maintained for each engine by following Special Instruction ?M0081144? ?Procedure to Measure Valve Recession for C175 Engines?.

3.) Measure and record recession on intake valves only on suspect cylinders if good records have been maintained on all intake valves. Once a baseline has been established, and good records are being kept and utilized on valve lash, it is only necessary to measure valve stem projection (valve recession) on those intake valves that show recession and are found to be tighter than the 0.028? (0.71 mm) specification during the normal valve lash measurement that occur every 4000 hours. If an intake valve is found to have greater than 1.6 mm of valve recession, the frequency of measurement should be increased to 2000 hours on that cylinder head/intake valves.

4.) The maximum amount of valve recession is limited to 2 mm (0.08 inch) of wear. The nominal head deck to valve stem tip measurement is 60.538 mm (2.383 inch). Zero-hour cylinder heads show a valve stem measurement of +0.2 to 0.3 mm per the gauge and tooling used in Special Instruction ?M0081144?. Any cylinder head with head deck to valve stem tip measurement that exceeds 62.538 mm (2.462 inch) should be replaced. This equates to -1.8 mm on the gauge and tooling used in Special Instruction ?M0081144?. As the recession is found to get closer to the 2 mm limit on valve recession the frequency of measurement on that particular cylinder should increase.

After Failure: The maximum amount of valve recession is limited to 2 mm (0.08 inch) of wear. The nominal head deck to valve stem tip measurement is 60.538 mm (2.383 inch). Any cylinder head with head deck to valve stem tip measurement that exceeds 62.538 mm (2.462 inch) should be replaced.

Note: Projection of wear at a given hour interval out to full life will not be allowed for head replacement. Only heads exceeding 2mm recession will be allowed.

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SERVICE CLAIM ALLOWANCES

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Product smu/age whichever comes first	Caterpillar		Dealer Suggested		Customer Suggested
Product smu/age whichever comes first	Parts %	Labor Hrs%	Parts %	Labor Hrs%	Parts %	Labor Hrs%
0-18000 hrs, 0-48 mo	100.0%	100.0%	0.0%	0.0%	0.0%	0.0%

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NOTE: This is a 5.0-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.
Before failure: 5 hours for measuring and recording the engine valve recession on all of the cylinder heads. Measurement Frequency: The normal valve lash adjustment frequency according the Operating and Maintenance Manual should be followed. This Service Letter is intended to support the additional work necessary to measure the valve stem projection or valve recession. If an intake valve is found to have greater than 1.6 mm of valve recession, the frequency of measurement should be increased to 2000 hours or less on that particular cylinder head/intake valves and depending on how close to 2 mm the recession value is. Service Letter can be claimed multiple times throughout the life of the engine. Provide measurement data to your Dealer Technical Communicator (TC) along with Machine Hours, Engine Hours, and Engine Serial Number. The Dealer TC will be responsible for reviewing the measurements and tracking valve recession over time, and providing this information to the Service Technical Representative on a regular basis. After failure: 6 hours per cylinder head replacement. Documentation of lash measurements and adjustment history on engine must be provided with claim. Multiple cylinder heads can be claimed so long as documentation is provided to justify the number of heads replaced. Service Letter can be claimed multiple times throughout the life of the engine so long as hours on the cylinder head is established. Projection of wear at a given hour interval out to full life will not be allowed for head replacement. Only heads exceeding 2mm recession will be allowed.