Exhaust System - Rattles/Buzzes At Idle/Start Up
TECHNICALBulletin No.: 08-06-05-006G
Date: July 20, 2011
Subject: Exhaust System Rattle, Buzz, Noise (Realign Exhaust System / Nut Replacement)
Models:
2007-2012 Chevrolet Colorado
2007-2012 GMC Canyon
Equipped with 2.9L or 3.7L Engine Only (VINs 9, E - RPOs LLV, LLR)
Supercede:
This bulletin is being revised to add the 2012 model year. Please discard Corporate Bulletin Number 08-06-05-006F (Section 06 - Engine/Propulsion System).
Condition
Some customers may comment on a rattle noise or buzz/vibration coming from under the vehicle during any of the following conditions:
- when vehicle is first started
- when vehicle is idling
- upon acceleration
Cause
This condition may be caused by a misalignment of the exhaust manifold assembly to the catalytic converter or exhaust system nuts not torqued properly. This could result in contact between the muffler (most forward hanger) and the frame and/or the catalytic converter pipe assembly to torsion bar and/or housing.
Correction
Important
DO NOT REPLACE THE EXHAUST SYSTEM OR MUFFLER FOR THIS CONDITION. Muffler assemblies should not be replaced for a loose nut or misalignment condition.
Inspect the exhaust system clearance at the following areas listed below.
Front Hanger to Frame Contact
1. Inspect the clearance between the frame and the muffler hanger.
Converter Pipe to Torsion Bar Housing
2. Inspect the clearance between the converter pipe and torsion bar housing.
Muffler Assembly Flange to Converter Assembly
3. Inspect the clearance between the muffler/converter assembly flange and crossmember.
4. If the clearance in these areas is greater than 15 mm (0.59 in), complete the following steps to correct the customer's concern.
1. Remove the nuts securing the muffler to the catalytic converter. Discard the nuts and clean the threads on the studs.
2. Install the NEW nuts securing the muffler to the catalytic converter.
Tighten:
Tighten the muffler nuts by hand until each contacts the metal flange.
Tighten:
Tighten the muffler nuts to 45 Nm (33 lb ft).
3. Verify if the customer's concern has been corrected.
5. If the clearance in these areas is less than 15 mm (0.59 in), complete the following exhaust system alignment procedure to correct the customer's concern.
1. Remove the nuts securing the muffler to the catalytic converter. Discard the nuts.
2. Position the muffler rearward enough to allow the studs located in the front to clear the catalytic converter pipe flange. Clean the threads on the studs.
3. Remove the three nuts attaching the catalytic converter to the exhaust manifold. Discard the nuts and clean the threads on the studs.
4. Lower the catalytic converter from the vehicle.
5. Remove the exhaust manifold seal from the exhaust manifold flange. Discard the seal.
6. Install the NEW seal to the exhaust manifold flange.
7. Position the catalytic converter to the exhaust manifold.
8. Install the three NEW nuts attaching the catalytic converter to the exhaust manifold. DO NOT tighten at this time.
9. Align the catalytic converter with the studs located in the front of the muffler.
10. Install the two NEW nuts securing the muffler to the catalytic converter.
Tighten:
Tighten the muffler nuts by hand until each contacts the metal flange.
Tighten:
Tighten the muffler nuts to 45 Nm (33 lb ft).
Tighten:
Tighten the catalytic converter nuts, previously installed in step 5.8, to 50 Nm (37 lb ft). Tighten the nuts in the following sequence: top nut, outboard nut, inboard nut.
11. Confirm that the clearances are now greater than 15 mm (0.59 in).
12. Verify if the customer's concern has been corrected.
Parts Information
Warranty Information
For vehicles repair under warranty, use the table.
Disclaimer