PRODUCT SUPPORT PROGRAM FOR REPLACING THE 1659118 PILOT UNLOADING VALVE ON CERTAIN 797 AND 797B OFF HIGHWAY TRUCKS

Usage:

SEBE9175

May 10, 2005
U-149
A-111
D-122
O-126

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*before or* *after failure*	PRODUCT SUPPORT PROGRAM FOR REPLACING THE 1659118 PILOT UNLOADING VALVE ON CERTAIN 797 AND 797B OFF HIGHWAY TRUCKS
5117		PS41819

NOTE: This Program can 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 "PS41819" as the Part number and "7755" as the Group Number. If administered before failure, use "56" as the Warranty Claim Description Code and use "T" as the SIMS Description Code. If administered after failure, use "96" as the Warranty Claim Description Code and use "Z" as the SIMS Description Code.

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.

TERMINATION DATE

November 30, 2005

PROBLEM

The Chassis Manifold Valve includes a brake charging valve that has caused brake system overheating because of a spool sticking condition in the valve that allows pump flow to dump to tank at high pressure. Spool sticking has also been found to cause erosion of the valve body. A solution for the problem is under investigation.

AFFECTED PRODUCT

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Model	Identification Number
797	5YW1-277
797B	JSM1-168

PARTS NEEDED

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Qty	Part Number	Description
1	1659118	Valve Gp.

ACTION REQUIRED

See the attached Rework Procedure.

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
0-40000	100%	1.0	0	0	0	0
NOTE: This is a 1.0 hr job.

NOTE: This program covers only the labor and authorized part. This program does not cover any contingent damage that may be associated with an after failure repair of the 165-9118 valve.

PARTS DISPOSITION

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

Attach. (1-Rework Procedure)

Rework Procedure

Replace the 1659118 Unloading Pilot Valve every 2000 hours or any time that failure of the brake charging system can be detected. This will eliminate the possibility of valve body erosion.

VIMS data can be used to determine whether or not the brake charging valve is in the initial stages of failure. A frequent occurrence of VIMS warnings, which are displayed to the operator as: "Brk Acum Pres Lo - Stop Safely" (a level 3 warning) or "Brk Acum Pres Lo - Do Not Move Machine" (a level 1 warning) indicate the early stage of charging valve failure. Frequent occurrence of VIMS warnings, which are displayed as "ParkBk On" (a level 1 or 2S warning) or "ParkBk Drag, Call Shop" (a level 1 warning) indicate later stages of charging valve failure.

Brake accumulator charging time can also be used to determine the condition of the charging valve. When a charging valve is in good condition, the brake accumulator charging time will be between 5 and 8 seconds at low idle engine speed. As the condition of the charging valve deteriorates, the brake accumulator charging time will become longer. At the worse condition of the charging valve, brake charging will not cutout. Charging time must be checked at low idle engine speed with warm hydraulic oil.