CAMPAIGN: FRT. BRAKE BRKT. MAY CRACK (INSPECT/REPLACE)

DEFECT INVOLVED GENERAL MOTORS HAS DETERMINED THAT A DEFECT WHICH RELATES TO MOTOR VEHICLE SAFETY EXISTS IN SOME 1983-1986 B6PO42 MODEL SCHOOL BUSES EQUIPPED WITH A 7500 LB. FRONT AXLE (RPO FRD), AND WITHOUT A FRONT BRAKE LIMITING VALVE (RPO J82). SEVERE BRAKE CHATTER MAY CAUSE THE BRAKE CHAMBER MOUNTING BRACKETS ON EITHER SIDE TO DEVELOP CRACKS IN THE WELD AREA WHERE THE S-CAM SHAFT TUBE ATTACHES TO THE CHAMBER SUPPORT SECTION. IF THIS CONDITION IS NOT CORRECTED, THE CRACK CAN GO ALL THE WAY THROUGH THE WELD CAUSING THE BRACKET TO BREAK, RESULTING IN THE LOSS OF BRAKING ABILITY AT THAT FRONT WHEEL, AND POSSIBLY RESTRICTED STEERING, WHICH COULD LEAD TO A VEHICLE CRASH WITHOUT PRIOR WARNING. TO PREVENT THIS CONDITION FROM OCCURRING IT WILL BE NECESSARY TO INSPECT, AND REPLACE AS NECESSARY, THE FRONT BRAKE CHAMBER MOUNTING BRACKETS AND INSTALL A FRONT BRAKE LIMITING VALVE ON ON INVOLVED VEHICLES. VEHICLES INVOLVED INVOLVED ARE CERTAIN MODEL B6PO42 SCHOOL BUSES EQUIPPED WITH A 7500 LB ROCKWELL FRONT AXLE (RPO FRD) AND WITHOUT A FRONT BRAKE LIMITING VALVE (RPO J82) BUILT WITHIN THE FOLLOWING VIN BREAKPOINTS: PLANT MODEL YEAR FROM THROUGH PONTIAC 1983 DV503715 DV534772 1984 EV500844 EV554094 1985 FV501543 FV632202 1986 GV501371 GV519558 THE SPECIFIC VEHICLES INVOLVED IN THIS CAMPAIGN HAVE BEEN IDENTIFIED BY VEHICLE IDENTIFICATION NUMBER COMPUTER LISTINGS. THESE LISTINGS ARE FURNISHED TO ALL INVOLVED DEALERS WITH THE CAMPAIGN BULLETIN. DEALER CAMPAIGN RESPONSIBILITY DEALERS ARE TO PERFORM THE REQUIRED SERVICE DESCRBIED UNDER SERVICE PROCEDURE FOR ALL VEHICLES SUBJECT TO THIS CAMPAIGN AT NO CHARGE TO OWNERS, REGARDLESS OF MILEAGE, AGE OF VEHICLE, OR OWNERSHIP, FROM THIS DAY FORWARD. WHENEVER A VEHICLE SUBJECT TO THIS CAMPAIGN IS TAKEN INTO YOUR NEW OR USED VEHICLE INVENTORY, OR IT IS IN YOUR DEALERHSHIP FOR SERVICE IN THE FUTURE, YOU SHOULD TAKE THE STEPS NECESSARY TO BE SURE THE CAMPAIGN CORRECTION HAS BEEN MADE BEFORE RESELLING OR RELEASING THE VEHICLE. OWNERS OF VEHICLES RECENTLY SOLD FROM YOUR NEW VEHICLE INVENTORY ARE TO BE CONTACTED BY THE DEALER, AND ARRANGEMENTS MADE TO MAKE THE REQUIRED MODIFICATION ACCORDING TO INSTRUCTIONS CONTAINED IN THIS BULLETIN. IF NO OWNER'S NAME AND ADDRESS WERE AVAILABLE TO GMC TRUCK AT THE TIME OF CAMPAIGN INITIATION, THE DEALER WILL DETERMINE THE OWNER'S NAME AND ADDRESS FROM THE DEALERSHIP SALES RECORDS. PLEASE PROVIDE THIS INFORMATION DIRECTLY ON THE SECOND COPY OF THE LISTING NEXT TO THE APPLICABLE VIN, SO THAT OUR RECORDS MAY BE UPDATED AND THE APPROPRIATE NOTIFICATION MAILED TO THE OWNER. THIS SECOND COPY SHOULD THEN BE SUBMITTED TO THE ADDRESS LISTED BELOW IN THE PREVIOUSLY SUPPLIED YELLOW CAMPAIGN ENVELOPES. GMC TRUCK GENERAL MOTORS CORPORATION 101 UNION STREET PLYMOUTH, MICHGIAN 48170 OWNER NOTIFICATION OWNERS WILL BE NOTIFIED OF THIS CAMPAIGN ON THEIR VEHICLES BY GMC TRUCK (SEE COPY OF OWNER LETTER INCLUDED WITH THIS BULLETIN). A LISTING OF OWNER NAMES AND ADDRESSES HAS BEEN FURNISHED TO THE INVOLVED DEALERS TO ENABLE DEALERS TO FOLLOW UP WITH OWNERS INVOLVED IN THIS CAMPAIGN. THIS LISTING MAY CONTAIN OWNER NAMES AND ADDRESSES OBTAINED FROM STATE MOTOR VEHICLE REGISTRATION RECORDS. THE USE OF SUCH MOTOR VEHICLE REGISTRATION DATA FOR ANY OTHER PURPOSE IS A VIOLATION OF LAW IN SEVERAL STATES. ACCORDINGLY, YOU ARE URGED TO LIMIT THE USE OF THIS LISTING TO THIS CAMPAIGN. SERVICE INFORMATION FOR REPAIR AND INSPECTION PROCEDURES, FOLLOW THE INSTRUCTION SHEETS 1 THROUGH 7 CONTAINED INT HIS BULLETIN. PARTS INFORMATION PARTS ARE TO BE OBTAINED FROM THE WAREHOUSING AND DISTRIBUTION DIVISION (WDDGM). TO ENSURE THT THESE PARTS WILL BE OBTAINED AS SOON AS POSSIBLE, THEY SHOULD BE ORDERED FROM WDDGM ON A C.I.O. ORDER WITH NO SPECIAL INSTRUCTION CODE, BUT ORDER ON AN ADVISE CODE (2). PART NO. DESCRIPTION QTY. PER VEHICLE 15559835 LIMITING VALVE INSTALLATION KIT 1 15515374 BRAKE CHAMBER BRACKET L.H. 1 (AS REQUIRED) W/MANUAL SLACK ADJ. 15515375 BRAKE CHAMBER BRACKET R.H. 1 (AS REQUIRED) W/MANUAL SLACK ADJ. 15512364 BRAKE CHAMBER BRACKET L.H. 1 (AS REQUIRED) W/AUTO SLACK ADJ 15512365 BRAKE CHAMBER BRACKET R.H. 1 (AS REQUIRED) W/AUTO SLACK ADJ. BRAKE CHAMBER BRACKETS WILL REQUIRE ZONE APPROVAL PRIOR TO PLACING AN{ ORDER WITH WDDGM. THERE IS NO RESTRICTION ON THE LIMITING VALVE KIT. WARRANTY INFORMATION DEALERS SHOULD SUBMIT AN ACCURATELY FILLED OUT WARRANTY REPAIR ORDER ON EACH VEHICLE COMPLETED UNDER THIS CAMPAIGN. LABOR OPERATION *TIME NET** TROUBLE NUMBER DESCRIPTION ALLOWANCE AMOUNT CODE V3470 INSTALL FRONT BRAKE 1.9 HRS. $6.75 96 LIMITING VALVE KIT. INSPECT BOTH BRAKE CHAMBER BRACKETS-REPLACE NEITHER. V3471 INSTALL FRONT BRAKE 2.9 HRS. $6.75 96 LIMITING VALVE KIT. INSPECT BOTH BRAKE CHAMBER BRACKETS-REPLACE ONE. V3472 INSTALL FRONT BRAKE LIMITING 3.8 HRS. $6.75 96 VALVE KIT. INSPECT BOTH BRAKE CHAMBER BRACKETS- REPLACE TWO. *FOR DEALER TO RECEIVE ADMINISTRATIVE TIME ALLOWANCE ASSOCIATED WITH THIS CAMPAIGN, ADD 0.1 HRS. TO THE LABOR OPERATION TIME ALLOWANCE. **THIS AMOUNT IS TO BE ENTERED IN THE NET ITEM AMOUNT ON THE WARRANTY CLAIM. IT INCLUDES CREDIT FOR DYE CHECK MATERIAL THAT MAY HAVE BEEN REQUIRED TO COMPLETE THIS CAMPAIGN. CAMPAIGN IDENTIFICATION LABEL EACH VEHICLE MODIFIED IN ACCORDANCE WITH THE INSTRUCTIONS OUTLINED IN THIS PRODUCT CAMPAIGN BULLETIN WILL REQUIRE A "CAMPAIGN IDENTIFICATION LABEL". EACH LABEL PROVIDES A SPACE TO INCLUDE THE FIVE (5) DIGIT DEALER CODE OF THE DEALER PERFORMING THE CAMPAIGN SERVICE. THIS INFORMATION MAY BE INSERTED WITH A TYPEWRITER OR BALLPOINT PEN. EACH "CAMPAIGN IDENTIFICATION LABEL" IS TO BE LOCATED ON THE RADIATOR CORE SUPPORT IN AN AREA WHICH WILL BE VISIBLE WHEN THE VEHICLE IS BROUGHT IN FOR PERIODIC SERVICING BY THE OWNER. APPLY "CAMPAIGN IDENTIFICATION LABEL" ONLY ON A CLEAN DRY SURFACE. ADMINISTRATIVE PROCEDURE PROCEDURES COVERING THIS CAMPAIGN ARE OUTLINED IN SECTION V OF YOUR DEALERSHIP'S "GMC TRUCK CLAIMS PROCESSING MANUAL" #SD8519. SERVICE PROCEDURE: NOTE: REFER TO THE MEDIUM DUTY SERVICE MANUAL SECTION 3 AND 5 FOR ADDITIONAL INFORMATION ON REMOVAL OR INSTALLATION PROCEDURES. ALWAYS ENSURE THAT THE BRAKE SYSTEM IS OPERATIONAL AFTER PERFORMING BRAKE WORK AND BEFORE RETURNING THE VEHICLE TO SERVICE. BRAKE CHAMBER MOUNTING BRACKET INSPECTION - RIGHT AND LEFT HAND SIDES O APPLY PARKING BRAKE. O CLEAN BRAKE CHAMBER MOUNTING BRACKET IN THE WELD WHERE THE S-CAM SHAFT TUBE ATTACHES TO THE CHAMBER SUPPORT SECTION OF ALL ROAD DIRT USING A WIRE BRUSH, SHEET 1 INSPECT THE WELD FOR CRACKS USING A DYE PENETRANT. FOLLOW THE INSTRUCTIONS SUPPLIED BY THE MANUFACTURER FOR SAFE AND CORRECT USE OF THE PRODUCT. O INSPECT BRACKET ON OPPOSITE WHEEL. O IF A BRACKET IS CRACKED REPLACE IT. BRAKE CHAMBER MOUNTING BRACKET REPLACEMENT O LIFT AND SUPPORT FRONT OF VEHICLE. O REMOVE WHEEL, HUB AND BRAKE DRUM ASSEMBLY. O REMOVE THE BRAKE SHOE RETURN AND HOLDDOWN SPRINGS. SWING BRAKE SHOES AWAY FROM THE BACKING PLATE TO PROVIDE ACCESS TO THE FOUR BRAKE CHAMBER BRACKET MOUNTING BOLTS. O REMOVE THE CLEVIS PIN FROM THE SLACK ADJUSTER. O REMOVE THE BRAKE CHAMBER FROM ITS MOUNTING BRACKET. CAREFULLY LAY CHAMBER ASIDE. O REMOVE THE SLACK ADJUSTER AND S-CAM. O REMOVE THE CRACKED BRAKE CHAMBER MOUNTING BRACKET FROM THE BRAKE BACKING PLATE AND DISCARD. O INSTALL NEW BRAKE CHAMBER BRACKET TO THE BACKING PLATE. TORQUE THE FOUR BOLTS TO 60 FT-LBS (80 N-M). O REINSTALL THE S-CAM AND SLACK ADJUSTER. O REINSTALL BRAKE CHAMBER TO ITS MOUNTING BRACKETR. TORQUE NUTS TO 33 FT-LBS (45 N-M). O REINSTALL SLACK ADJUSTER CLEVIS PIN AND THE BRAKE SHOE SPRINGS. O CLEAN AND PACK THE WHEEL BEARINGS AND INSTALL A NEW GREASE SEAL IN THE HUB. O REINSTALL WHEEL, HUB AND BRAKE DRUM ASSEMBLY. O LUBRICATE THE SLACK ADJUSTER AND THE BRAKE CHAMBER MOUNTING BRACKET USING A CHASSIS LUBRICANT, PN 1052182 OR EQUIVALENT. O ADJUST BRAKES AS REQUIRED. LIMITING VALVE INSTALLATION - REQUIRED ON ALL VEHICLES O DISCONNECT THE NEGATIVE BATTERY CABLE. O DISCONNECT THE THREE AIR LINES AT THE QUICK RELEASE VALVE WHICH IS MOUNTED ON THE FRONT CROSSMEMEBER, SHEET 1 ORIGINAL INSTALLATION. O REMOVE THE QUICK RELEASE VALVE FROM ITS MOUNTING BRACKET. O REMOVE THE UPPER ELBOW FROM THE QUICK RELEASE VALVE, SEAL USING LOCTITE PIPE SEALANT, PN 1052080 OR EQUIVALENT, AND REINSTALL AS SHOWN IN SHEET 2 AIR LINE INSTALLATION. THE ELBOW WILL BE ROTATED 180 DEGREES FROM ITS ORIGINAL POSITION. O DISCONNECT THE AIR DELIVERY LINE AT THE FRAME RAIL FITTING AND DISCARD LINE. O INSTALL A NEW SLEEVE AND NUT, PART OF ELBOW ASSEMBLY 055000, ON COPPER SUPPLY LINE PN 2080428 AND CONNECT TO THE EXISTING ELBOW AT THE FRAME RAIL. O SEAL TWO NEW ELBOWS AND INSTALL IN LIMITING VALVE AS SHOWN IN SHEET 2 AIR LINE INSTALLATION. O INSTALL LIMITING VALVE BRACKET TO THE FRONT CROSSMEMBER IN EXISTING HOLES, SHEET 2 VIEW A. TORQUE NUTS 30-33 FT-LBS (40-45 N-M). O INSTALL LIMITING VALVE TO ITS BRACKET, SHEET 2 VIEW A. TORQUE NUTS 15-20 FT-LBS (20-25 N-M). O REINSTALL QUICK RELEASE VALVE TO ITS BRACKET, SHEET 2 VIEW A. TORQUE NUTS 15-20 FT-LBS (20-25 N-N). O CONNECT AIR SUPPLY LINE TO THE LIMITING VALVE ELBOW, SHEET 2 AIR LINE INSALLATION. NOTE: COPPER LINES SHOULD NOT RUB ON ANY OTHER PART. O CLIP AIR SUPPLY LINE TO THE FRAME RAIL USING THE EXISING CLIP AND ATTACHING HARDWARE. O INSTALL NEW SLEEVES AND NUTS ON COPPER LINE PN 2080434 AND CONNECT TO THE QUICK RELEASE VALVE AND THE LIMITING VALVE, SHEET 2 AIR LINE INSTALLATION. O CONNECT AND TIGHTEN EXISTING LINES TO THE QUICK RELEASE VALVE, SHEET 2 AIR LINE INSTALLATION. O CONNECT NEGATIVE BATTERY CABLE. O INSPECT BRAKE LINES AND CONNECTIONS FOR AIR LEAKS USING SOAP SUDS. MAKE SEVERAL BRAKE APPLICATIONS TO ENSURE THAT LEAKS DO NOT EXIST IN THE LINES OR FITTINGS WITH FULL SYSTEM AIR PRESSURE 120 PSI.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.