Exhaust System - Rattle/Rumble Noise
File in Section: 06 - Engine/Propulsion SystemBulletin No.: 01-06-05-006
Date: November, 2001
TECHNICAL
Subject:
Exhaust System Rumble/Rattle Noise
(Replace Exhaust Pipe Seals and Modify Exhaust Pipe Ring Flanges)
Models:
1996-1998 Chevrolet and GMC C/K Models with 4.3L Engine (VIN W - RPO L35)
1996-1999 Chevrolet and GMC C/K Models (Old Style) with 5.0L
or 5.7L Engine (VINs M, R - RPOs L30, L31)
2000 Chevrolet and GMC C/K Models (Old Style)
with 5.7L Engine (VIN R - RPO L31)
1996-2002 Chevrolet and GMC G-Vans with 4.3L, 5.0L
or 5.7L Engine (VINs W, M, R - RPOs L35, L30 or L31)
1996-2002 Chevrolet and GMC S/T, M/L Models
with 4.3L Engine (VIN W - RPO L35)
1999-2000 Cadillac Escalade
1996-2002 Oldsmobile Bravada
Condition
Some customers may comment on a rumble/rattle type noise that is audible in the vehicle passenger compartment when the engine is idling, the transmission is in Drive and the service brakes are applied. High ambient temperatures and A/C compressor cycling may further aggravate this condition.
Cause
This condition may be the result of inadequate clampload on the exhaust pipe seals at the exhaust pipe/manifold joint. The low seal clampload may be the result of the standoffs on either one or both of the exhaust pipe ring flanges contacting the exhaust manifold.
Correction
This condition can be corrected by replacing the existing exhaust pipe seals with new seals, P/N 15093974, and modifying the exhaust pipe ring flanges. The ring flange modification consists of reducing the height of all three of the standoffs on both of the exhaust pipe ring flanges by 2 mm (0.08 in). Follow the procedure below.
1. Following the Service Manual procedure, lower the exhaust system down enough to access the exhaust pipe ring flanges.
2. Remove and discard the existing exhaust pipe seals.
3. With the ring flanges slid down the exhaust pipe, mark each of the three standoffs on both the rings 2 mm (0.08 in) down from the surface that faces the exhaust manifold.
4. Grind the ring flange standoffs to the marks established in the previous step on both of the flanges.
5. Install new exhaust pipe seals, P/N 15093974.
6. Raise the exhaust pipe into position and hand start the ring flange to exhaust manifold fasteners.
Notice:
Use the tightening sequence and specifications shown when installing fasteners in order to avoid damage to parts and systems. If exhaust system is disconnected at any location other than at the exhaust seal, gasket and exhaust system alignment may be required.
7. Following the fastener tightening sequence, gradually draw the ring flanges toward the exhaust manifold seal faces, maintaining the ring flanges as parallel to the manifold faces as possible.
Tighten
Tighten the exhaust ring flange to exhaust manifold fasteners to the specification indicated by vehicle year and model shown.
Parts Information
Parts are currently available from GMSPO.
Warranty Information
For vehicles repaired under warranty, use the table shown.
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