EXHAUST HEAT SHIELD RATTLE (INSTALL NEW SHIELD & CLAMPS)

SUBJECT: EXHAUST HEAT SHIELD CRACKING (CLAMP SHIELD)

VEHICLES AFFECTED: 1990-91 6H, 7H TOPKICK M/D TRUCKS W/CAT 3116 DIESEL ENGINES VIN J RPO LXO -----------------------------------------------------------------------------

Some 1990-91 6H, 7H Topkick medium duty trucks with CAT 3116 diesel engines may experience an exhaust heat shield cracking at any or all of the "legs" which affix the shield to the exhaust pipe Refer to Figure 1.

The expansion rate of the exhaust pipe and the shield are different which can create a condition where the heat shield cracks.

Vehicles produced after February 19, 1991 (Job #18379) have a new exhaust pipe with a revised heat shield, which is attached in the centre and is not subject to the same thermal expansion condition.

For vehicles built prior to February 19, 1991 which exhibit one or more heat shield mounting pads (legs) cracked, the following service procedure should be followed.

SERVICE PROCEDURE:

1. Disconnect the negative battery cable from the battery.

2. Refer to Figure 2 for location, remove and discard the existing heat shield clamps. (Clamps may not be installed on all models.)

3. Remove and discard the existing heat shield by breaking welds or cutting off the mounting legs.

4. Referring to Figure 2, section A-A, install replacement heat shield (2) in such a manner as to provide maximum protection to the wiring. For proper horizontal location, align the edge of the heat shield (2) with the remaining weld nuggets from step 3.

5. Install replacement clamps (1) with washers (3) as shown in Figure 2, section A-A, and torque to 20-27 N.m. (15-20 lbs. ft.).

6. Reconnect the negative battery cable to the battery.

SERVICE PARTS INFORMATION

Part Number Description Quantity ----------- ----------- -------- 791786 Clamp Assembly 2 15687429 Exhaust Heat Shield 1 15614758 Washer-Flat 8

Parts are currently available from CANSPO.

WARRANTY INFORMATION

For vehicles repaired under warranty use:

Labour Time: 0.3 hrs.

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.