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Emissions / Exhaust

GM Tech Tip: Heat Shield Buzz During Operation

Some customers may comment on a pinging/popping/snapping noise from underneath the vehicle at idle or immediately after the vehicle is shut off. A pinging/popping/snapping noise from the exhaust system during cooldown is a normal condition.

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Models:
2007-2011 Cadillac Escalade, Escalade Hybrid, Escalade ESV, Escalade EXT
2007-2011 Chevrolet Avalanche, Silverado, Suburban, Tahoe, Tahoe Hybrid
2007-2011 GMC Sierra, Sierra Denali, Yukon, Yukon Hybrid, Yukon XL, Yukon Denali

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Condition 1

Some customers may comment on a pinging/popping/snapping noise from underneath the vehicle at idle or immediately after the vehicle is shut off. A pinging/popping/snapping noise from the exhaust system during cooldown is a normal condition. The noise may be intermittent depending on the outside temperature and/or temperature of the exhaust system at the time of testing.

Cause 1 – Exhaust Pinging/Popping/Snapping

As the exhaust system cools, the muffler shell and muffler internals contract at different rates. The noise from the exhaust system during cooldown is a normal condition.

Correction 1

Note: Do not replace the exhaust system components.

This condition is normal to the muffler design and does not indicate poor quality or part failure. No repairs are necessary for this condition. Replacing the muffler heat shield straps will NOT eliminate this noise. A new muffler may sound quiet for this condition, but as it ages, it may again produce this same condition.

Condition 2

Some customers may also comment on a buzz noise coming from the muffler during vehicle operation.

Cause 2 – Muffler Heat Shield Buzz

If the muffler heat shield straps are loose, the heat shield may be free to buzz during vehicle operation.

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Correction 2

NOTE: DO NOT REPLACE THE EXHAUST SYSTEM COMPONENTS.

Confirm the origin of the buzz by shimming (use metal shims) the straps tight and rerunning the vehicle. If the buzz concern is gone, then it is caused by the loose shield. Using the following procedure, install new straps to secure the heat shield to the muffler.

gmc heat shield 1

1. Raise and support the vehicle.

2. Mark the position of the heat shield (1) and straps (2) on the muffler shell.

3. Cut and remove the heat shield straps using tin snips along the muffler shell seam (1), and remove the shield from the muffler.

4. Position the heat shield to the muffler and install new heat shield straps on the muffler shell in the positions marked prior to removal.
Important: Do not position the strap screw heads directly across from the propeller shaft. Ensure the strap heads are positioned below the midpoint of the muffler.

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5. Position the strap screw heads (1) on the inboard side of the muffler. Ensure that the strap screw heads (1) are below the midpoint of the muffler. Tighten the straps to 4 Nm (35 lb/in).

6. Cut off the excess strap material and ensure that the ends (2) are flat against the muffler.

Courtesy of ALLDATA.

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