AIR BRAKE PRESSURE DOES NOT INCREASE AFTER COLD START. GMC Truck GMC MD Conventional (C Model) 1996

SUBJECT: AIR BRAKE PRESSURE DOES NOT INCREASE AFTER COLD START (INSTALL REVISED PIPE AND HOSE ASSEMBLY)

MODELS: 1994-96 CHEVROLET KODIAK AND GMC TOPKICK MEDIUM DUTY TRUCKS WITH 3116 CATERPILLAR DIESEL ENGINE (VIN J - RPO LX0) AND AIR BRAKES (RPO JE4) AND AIR DRYER (RPO JTT)

CONDITION:

SOME CUSTOMERS MAY REPORT THAT WHEN THE AMBIENT TEMPERATURE FALLS BELOW FREEZING, THE AIR BRAKE SYSTEM DOES NOT BUILD UP AIR PRESSURE AFTER INITIAL ENGINE START.

CAUSE:

EXCESS MOISTURE COLLECTS AND FREEZES IN A LOW SECTION OF THE LINE BETWEEN THE AIR COMPRESSOR AND THE AIR DRYER BLOCKING THE PASSAGE. THIS BLOCKAGE PREVENTS THE AIR COMPRESSOR FROM RAISING THE PRESSURE IN THE AIR TANKS.

CORRECTION:

REPLACE THE AIR COMPRESSOR DISCHARGE PIPE AND HOSE ASSEMBLY WITH THE PART NUMBERS LISTED BELOW. THIS NEW ASSEMBLY FEATURES A ROUTING THAT GOES DIRECTLY DOWN THE LEFT FRAME RAIL TO THE AIR DRYER ELIMINATING THE LOW SECTION WERE MOISTURE COULD COLLECT. SEE FIGURES 1 AND 2.

SERVICE PROCEDURE:

REFER TO THE APPROPRIATE YEAR AND MODEL MEDIUM DUTY TRUCK SERVICE MANUAL, SECTION 5G, AIR BRAKES, ON VEHICLE SERVICE.

IMPORTANT: THE PIPE AND HOSE ASSEMBLY MUST BE PROPERLY SUPPORTED OVER ITS ENTIRE LENGTH AND HAVE ADEQUATE CLEARANCE FROM THE FRAME RAIL AND COMPONENTS TO PREVENT CONTACT.

PARTS INFORMATION:

P/N DESCRIPTION QTY

15026387 PIPE; AIR COMP. DISCHARGE 1

15957444 CONNECTOR; AIR COMPRESSOR 1 DISCHARGE PIPE

15026388 BRACKET; AIR COMPRESSOR 1 DISCHARGE PIPE

09419030 BOLT; HEX-BRACKET TO COMP. 2

15531203 WASHER; FLAT-BRACKET TO COMP. 2

15651066 CLIP; PIPE TO BRACKET 2

11500760 NUT; M8-PIPE TO BRACKET 2

15531203 WASHER; FLAT-PIPE TO BRACKET 4

11514766 BOLT; PIPE TO BRACKET 2 M8 X 1.25"

15028511 HOSE; AIR COMP. DISCHARGE 1

15734590 STRAP-TIE (BUTTON HEAD) 1

15028510 ELBOW; DISCHARGE HOSE 1 TO DRYER

PARTS WILL BE AVAILABLE FROM GMSPO ON NOVEMBER 11, 1996

WARRANTY INFORMATION:

FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OP DESCRIPTION LABOR TIME H1722 LINE, AIR BRAKE USE PUBLISHED REPAIR OR REPLACE LABOR OPERATION TIME

IMPORTANT: LABOR OPERATION IS CODED TO BASE VEHICLE COVERAGE IN THE WARRANTY SYSTEM.

FIGURES: 2

CAPTIONS: FIGURE 1 1. BRACKET; AIR COMPRESSOR DISCHARGE PIPE 2. HOSE; AIR COMP. DISCHARGE 3. PIPE; AIR COMP. DISCHARGE 4. AIR COMPRESSOR

FIGURE 2 1. HOSE; AIR COMP. DISCHARGE 2. ELBOW; DISCHARGE HOSE TO DRYER 3. AIR DRYER

Object Number: 96529 Size: FS

Object Number: 96530 Size: FS

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.