CAMPAIGN: AIR COMPRESSOR MOUNT BRACKET BOLTS MAY LOOSEN

SUBJECT: AIR COMPRESSOR MOUNTING BRACKET 1987-88 C6/C7, B6, S7, AND P6 WITH 8.2L DIESEL ENGINES (LH3/LH4) AND ONE PIECE AIR COMPRESSOR MOUNTING BRACKET (KYA/K55/K56)

GENERAL MOTORS HAD DETERMINED THAT CERTAIN 1987-88 MEDIUM DUTY TRUCKS EQUIPPED WITH 8.2L DIESEL ENGINES (LH3/LH4) AND BUILT WITH ONE PIECE AIR COMPRESSOR BRACKETS (P/N 15556206) MAY BE SUBJECT TO THE AIR COMPRESSOR MOUNTING BRACKET BOLTS LOOSENING. THE LOOSENING OF THE BRACKET IS THE RESULT OF AN INTERFERENCE BETWEEN A WEB ON THE BRACKET AND A BOSS ON THE LEFT-HAND INTAKE MANIFOLD OF THE ENGINE. ALTHOUGH PROPER BOLT TORQUE WAS ACHIEVED DURING ASSEMBLY, THE POINT CONTACT ON THE WEB CAN WEAR FROM NORMAL ENGINE VIBRATION WHICH CAUSES LOSS OF CLAMP LOAD. THE LOSS OF CLAMP LOAD CAN ELONGATE THE BRACKET BOLT HOLES AND ULTIMATELY RESULT IN BOLT BREAKAGE AND THE BRACKET SEPARATING FROM THE ENGINE CAUSING A LOSS OF COMPRESSOR FUNCTION. ADDITIONALLY, THIS SEAPRATION CAN SEVER THE COMPRESSOR OIL SUPPLY LINE CAUSING LOSS OF ENGINE OIL AND SEVERE ENGINE DAMAGE.

IF THIS CONDITION SHOULD OCCUR, NOISE FROM THE COMPRESSOR FALLING LOOSE MAY BE NOTED. THE LOW AIR PRESSURE WARNING LIGHT AND BUZZER ON THE INSTRUMENT PANEL WILL ACTIVATE ALTHOUGH THE ACCUMULATED AIR PRESSURE IN THE SEPARATE AIR RESERVOIRS FOR THE FRONT AND REAR BRAKE SYSTEMS WILL NOT BEGIN TO BE DEPLETED UNTIL BRAKE APPLICATION. AFTER EIGHT FULL BRAKE APPLICATIONS THE RESERVOIRS' AIR PRESSURE IS SO DEPLETED THAT THE REAR SPRING BRAKES AUTOMATICALLY APPLY. THE TRUCK MUST BE REAPIRED BEFORE FURTHER OPERATION.

IT WILL BE NECESSARY TO CHECK FOR INTERFERENCE BETWEEN THE ENGINE LEFT BANK INTAKE MANIFOLD AND AIR COMPRESSOR BRACKET; IF NECESSARY GRIND/REWORK THE AIR COMPRESSOR MOUNTING BRACKET OR REPLACE THE MOUNTING BRACKET IF THE BRACKET BOLT HOLES ARE OBLONG FROM THE BRACKET BEING LOOSE.

VEHICLES INVOLVED

INVOLVED ARE 1987-88 GMC AND CHEVROLET MEDIUM DUTY MODEL TRUCKS EQUIPPED WITH 8.2L DIESEL ENGINES (LH3/LH4) AND ONE PIECE AIR COMPRESSOR BRACKETS (KYA/K55/K56) BUILT WITHIN THE FOLLOWING VIN BREAKPOINTS:

MODEL YEAR MODEL PLANT FROM THROUGH

1987 CHEVROLET PONTIAC HV105486 HV117662 1987 GMC PONTIAC HV519639 HV541293 1988 CHEVROLET PONTIAC JV100021 JV102763 1988 GMC PONTIAC JV500005 JV504756

THE SPECIFIC VEHICLES INVOLVED IN THIS CAMPAIGN HAVE BEEN IDENTIFIED BY VIN NUMBER COMPUTER LISTINGS. THESE LISTINGS ARE FURNISHED TO ALL INVOLVED DEALERS WITH THE CAMPAIGN BULLETIN.

DEALER CAMPAIGN RESPONSIBILITY

DEALERS ARE TO SERVICE ALL VEHICLES SUBJECT TO THIS CAMPAIGN AT NO CHARGE TO OWNERS, REGARDLESS OF MILEAGE, AGE OF VEHICLE, OR OWNERSHIP, FROM THIS TIME FORWARD.

WHENEVER A VEHICLE SUBJECT TO THIS CAMPAIGN IS TAKEN INTO YOUR NEW OR USED VEHICLE INVENTORY, OR IT IS IN YOUR DEALERSHIP 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 CORRECTION ACCORDING TO INSTRUCTIONS CONTAINED IN THIS BULLETIN.

IF AN OWNER'S NAME AND ADDRESS WAS NOT 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 A SECOND COPY OF THE LISTING MEXT 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 DIVISION GENERAL MOTORS CORPORATION 101 UNION STREET PLYMOUTH, MICHIGAN 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

LISTED BELOW ARE TWO POSSIBLE CONDITIONS WHICH MAY CREATE POOR BOLT DURABILITY AND THE REPAIR RECOMMENDED.

1. INTERFERENCE BETWEEN ENGINE LIFT BANK INTAKE MANIFOLD AND AIR COMPRESSOR BRACKET RESULTING IN FALSE BOLT TORQUE READING.

A. CHECK FOR PROPER CLEARANCE (.020) FEELER GAGE BETWEEN THE COMPRESSOR MOUNTING BRACKET AND THE FRONT OF THE LEFT BANK INTAKE MANIFOLD WITH A FEELER GAGE. SEE FIGURE NO. 1 (IF OK, PROCEED TO ITEM 2). IF THE (.020) FEELER GAGE DOES NOT FIT, REMOVE THE AIR COMPRESSOR MOUNTING BRACKET AND GRIND APPROXIMATELY 3MM OR 1/8" FROM THE RIB ABOVE #10 BOLT APPROXIMATELY 2" IN LENGTH AS SHOWN IN FIGURE NO. 2. IT IS IMPORTANT THAT THIS REWORK AREA BE SMOOTH AND FREE OF SHARP CORNERS. AFTER REWORK HAS BEEN COMPLETED, INSTALL NEW MOUNTING BOLTS.

NOTICE: TO HELP AVOID PROPERTY DAMAGE, DO NOT GRIND ACROSS THE WEB. GRIND THE WEB IN AN UPWARD OR DOWNWARD MOTION.

B. IF THE AIR COMPRESSOR BRACKET CONTACTS THE FRONT OF THE MANIFOLD OR IF IT IS LOOSE, CHECK FOR OBLONG HOLES AT BOLT HOLES #7, #9, AND #10. SEE FIGURE NO. 3. IF THE BOLT HOLES ARE OBLONG, REPLACE THE BRACKET AND INSTALL NEW MOUNTING BOLTS. IF THE BRACKET IS REPLACED, INSPECTION FOR PROPER CLEARANCES (#1A ABOVE) MUST BE REPEATED.

2. IMPROPER MOUNTING BRACKET ATTACHING BOLTS AND TORQUE.

A. TO DETERMINE IF THE PROPER BOLTS WERE INSTALLED, THE NUMBERS ON THE HEAD OF THE BOLT MUST BE INSPECTED. WITH THE EXCEPTION OF BOLT #7 IN FIGURE NO. 3, ALL BOLTS SHOULD BE 9.8 GRADE AND 9.8 SHOULD BE CAST ON THE HEAD OF THE BOLT. BOLT #7 SHOULD BE 10.9 GRADE AND MAY BE 75MM OR 80MM IN LENGTH, EITHER OF WHICH IS CORRECT. IF AN IMPROPER BOLT IS FOUND DURING INSPECTION, IT SHOULD BE REPLACED AND TORQUED TO THE SPECIFICATION LISTED BELOW:

NOTICE: TO HELP AVOID PROPERTY DAMAGE, USE THE CORRECT BOLT TORQUE FOR ALL BOLTS. BOLT TORQUE SPECIFICATIONS FOR 9.8 GRADE BOLTS ARE DIFFERENT THAN FOR 10.9 GRAKE BOLTS.

B. ASSOCIATED FASTENERS AND TORQUE SPECIFICATIONS ARE LISTED BELOW. IT IS IMPORTANT THAT THE PROPER GRADE BOLT IS USED ON THE MOUNTING BRACKET INSTALLATION.

ITEM # QTY P/N DESCRIPTION GRADE SPECIFICATION 10 1 11513588 BOLT M10X1.5X40MM 9.8 45 NM (35 LBS FT) 9 2 11508110 BOLT M10X1.5X55MM 9.8 45 NM (35 LBS FT) 7 1 11503649 BOLT M10X1.5X75MM 10.9 62 NM (45 LBS FT) 3 5 11509161 WASHER 11.0X21.8X 2.9 (1050-1080)

PARTS INFORMATION

PARTS REQUIRED TO COMPLETE THIS CAMPAIGN ARE TO BE OBTAINED FROM GMSPO. TO ENSURE THESE PARTS WILL BE OBTAINED AS SOON AS POSSIBLE, THEY SHOULD BE ORDERED FROM GMSPO ON A "C.I.O." ORDER WITH NO SPECIAL INSTRUCTION CODE, BUT ON AN ADVISE CODE 2.

QUANTITY/ PART NUMBER DESCRIPTION VEHICLE

11513588 BOLT M10X1.5X40MM 1 11508110 BOLT M10X1.5X55MM 2 11503649 BOLT M10X1.5X75MM 1 11504596 BOLT M10X1.5X25MM 1 PUR. LOC. BOLT 3/3-16X1-3/4 (280MM) 2 11509161 WASHER 11.0X21.8X2.9 5 15556206 SUPPORT AIR COMPRESSOR 1 15608861 SUPPORT - BELT TENSIONER 1 2050481 TENSIONER ASSEMBLY - BELT 1 15556625 SPACER - BELT TENSIONER 1

WARRANTY INFORMATION

DEALERS SHOULD SUBMIT A WARRANTY CLAIM ON EACH VEHICLE COMPLETED UNDER THIS CAMPAIGN.

LABOR OPERATION *TIME TROUBLE NUMBER DESCRIPTION ALLOWANCE CODE

V4730 INSPECT BRACKET FOR PROPER 0.2 HRS 96 CLEARANCES AND BOLT HOLE ELONGATON; INSPECT FOR PROPER BOLTS; NO FURTHER ACTION NECESSARY

V4731 INSPECT BRACKET FOR NECESSARY 1.0 HRS 96 CLEARANCE (SEE BELOW IF BOLT HOLE(S) ELONGATED) AND REMOVE BRACKET, GRIND BRACKET, REINSTALL BRACKET, INSPECT BOLTS.

V4732 INSPECT BRACKET FOR NECESSARY 0.3 HRS 96 CLEARANCE; OR REMOVE AND REPLACE ONE BOLT.

ANY ADDITIONAL BOLT(S) - ADD 0.1 HRS

V4733 INSPECT BRACKET - NECESSARY 1.2 HRS 96 TO REPLACE DUE TO BOLT HOLE(S) ELONGATED. SEPARATION OF AIR COMPRESSOR IS REQUIRED.

* FOR DEALERS TO RECEIVE ADMINISTRATIVE TIME ALLOWANCE ASSOCIATED WITH THIS CAMPAIGN, ADD 0.1 HOURS TO THE LABOR OPERATION TIME ALLOWANCE.

CAMPAIGN IDENTIFICATION LABEL

EACH VEHICLE CORRECTED 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 A BALL POINT 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 #P8719.

GMC DISCLAIMER

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.