BODY 6N4080 - Caterpillar

May 10, 2005
U-149
A-111
D-122
O-126
beforeor
after failure PRODUCT SUPPORT PROGRAM FOR REPLACINGTHE 1659118 PILOT UNLOADING VALVE ON CERTAIN 797 AND 797B OFF HIGHWAY TRUCKS
5117 PS41819
This Program can be administered eitherbefore or after failure. In either case the decision whether to apply theProgram is made by the dealer. When reporting the repair, use "PS41819"as the Part number and "7755" as the Group Number. If administered beforefailure, use "56" as the Warranty Claim Description Code and use "T" asthe SIMS Description Code. If administered after failure, use "96" as theWarranty Claim Description Code and use "Z" as the SIMS Description Code. The information supplied in this serviceletter may not be valid after the termination date of this program. Donot perform the work outlined in this Service Letter after the terminationdate without first contacting your Caterpillar product analyst.TERMINATION DATE
November 30, 2005PROBLEM
The Chassis Manifold Valve includes a brake chargingvalve that has caused brake system overheating because of a spool stickingcondition 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
Model Identification Number
797 5YW1-277
797B JSM1-168PARTS NEEDED
Qty
Part Number Description
1 1659118 Valve Gp.ACTION REQUIRED
See the attached Rework Procedure.SERVICE CLAIM ALLOWANCES
Product smu/age whichever comes first Caterpillar Dealer Suggested Customer Suggested
Parts Labor Hrs Parts Labor Hrs Parts Labor Hrs
0-40000 100% 1.0 0 0 0 0
This is a 1.0 hr job. This program covers only the laborand authorized part. This program does not cover any contingent damagethat may be associated with an after failure repair of the 165-9118 valve.PARTS DISPOSITION
Handle the parts in accordance with your WarrantyBulletin on warranty parts handling.Attach. (1-Rework Procedure)Rework Procedure
Replace the 1659118 Unloading Pilot Valve every2000 hours or any time that failure of the brake charging system can bedetected. This will eliminate the possibility of valve body erosion.VIMS data can be used to determine whetheror not the brake charging valve is in the initial stages of failure. Afrequent occurrence of VIMS warnings, which are displayed to the operatoras: "Brk Acum Pres Lo - Stop Safely" (a level 3 warning) or "Brk Acum PresLo - Do Not Move Machine" (a level 1 warning) indicate the early stageof charging valve failure. Frequent occurrence of VIMS warnings, whichare displayed as "ParkBk On" (a level 1 or 2S warning) or "ParkBk Drag,Call Shop" (a level 1 warning) indicate later stages of charging valvefailure.Brake accumulator charging time can alsobe used to determine the condition of the charging valve. When a chargingvalve is in good condition, the brake accumulator charging time will bebetween 5 and 8 seconds at low idle engine speed. As the condition of thecharging valve deteriorates, the brake accumulator charging time will becomelonger. At the worse condition of the charging valve, brake charging willnot cutout. Charging time must be checked at low idle engine speed withwarm hydraulic oil.