Boom Type Noise During Engine Warm-Up (Install Exhaust Dampener Assembly)

This bulletin is being revised to add the 2005 model year. Please discard Corporate Bulletin Number 00-06-05-001A (Section 06 -- Engine/Propulsion System).

Some customers may comment on a boom type noise heard in the vehicle passenger compartment during engine warm-up.

Install an exhaust dampener assembly on affected vehicles. Use the following procedure and the part numbers listed below.

1. Raise and suitably support the vehicle. Refer to the General Information subsection of the applicable Service Manual for information on lifting and jacking the vehicle.




Important: The exhaust dampener weight must face forward.

2. Position the exhaust dampener assembly on the catalytic converter pipe assembly approximately 90 mm (4 in) forward of the outlet flange.
3. Hand tighten the clamp nut and the dampener weight while maintaining the proper position. Install three 3/8" inside diameter and 1/16" thickness flat washers, P/N 11509161, or equivalent between the top of the dampener and the heat shield plate.

Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

4. Install the 3/8" inside diameter lock washer, P/N 11500046, or equivalent and jam nut.

Tighten
Tighten the clamp nut and the jam nut to 30 N·m (22 lb ft).

5. Lower the vehicle.

Parts are currently available from GMSPO.

For vehicles repaired under warranty, use: