The plenum lower is formed from laminated steel. This steel is constructed by bonding 2 pieces of cold rolled steel (1) with a viscoelastic layer of adhesive (2). MIG welding laminated steel does not meet GM Corporate standards for structural integrity. As an alternative, all factory welds may be replaced by using the rivet and adhesive bond method described in the installation portion of this procedure. The rivet and adhesive bond method must only be used in the areas described in this procedure.

Caution: Refer to Approved Equipment for Collision Repair Caution in the Preface section.

1. Disable the SIR system. Refer to SIR Disabling and Enabling .
2. Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection .
3. Remove all related panels and components to gain access to the upper plenum panel.
4. Remove the sealers and anti-corrosion materials from the repair area, as necessary. Refer to Anti-Corrosion Treatment and Repair .




Important: Drill through the upper plenum flange only. Do not drill into the attaching panels.

5. Using an 8 mm (5/16 in) spot weld remover, locate and drill out the factory welds on the weld flange connecting the upper plenum to the dash panel and the lower plenum.



6. Reposition the body side and the windshield flange to aid with the removal of the upper plenum.



7. Remove the damaged upper plenum panel from the vehicle.

1. Position the service upper plenum in the vehicle using 3-dimensional measuring equipment. Clamp into place.



2. Using a 7 mm (17/64 in) drill bit, drill the rivet attachment holes through the service upper plenum and into the lower plenum in the locations noted from the original panel.



3. Unclamp the upper plenum. Remove the plenum from the vehicle.



4. Drill 8 mm (5/16 in) plug weld holes in the service part in the locations noted from the original panel in areas where the panel did not attach to the lower plenum.
5. Prepare the MIG-weld mating surfaces as necessary.
6. Apply GM-approved Weld-Thru Coating or equivalent to all mating surfaces. Refer to Anti-Corrosion Treatment and Repair .




Important: Do not damage the corners or thin the metal during the grinding process.

7. Prepare the bonding mating areas by grinding the flanges to bare steel.



8. Apply a 3-6 mm (1/8-1/4 in) bead of metal bonding adhesive GM P/N 12378567 or equivalent to the mating surfaces of the lower plenum and the upper plenum panel.



9. Using a small acid brush, spread a coating of adhesive on the mating surfaces. Cover all of the bare metal to ensure corrosion protection.



10. Apply a 3-6 mm (1/8-1/4) bead of metal bonding adhesive to the lower plenum. Refer to Anti-Corrosion Treatment and Repair .

Important: Do not pull the upper plenum from the lower plenum once installed. To align the panels, slide the panels into place.




11. Position the service upper plenum to the vehicle using 3-dimensional measuring equipment. Clamp the upper plenum into place.

Important: Verify the proper position of the upper plenum prior to riveting and welding.




12. Install rivets between the upper and lower plenums.
13. Remove the excess adhesive from the rivet bond area.



14. Locate the remaining holes in the upper plenum. Plug weld accordingly.
15. Clean and prepare all of the welded surfaces.
16. Apply the sealers and anti-corrosion materials to the repair area, as necessary. Refer to Anti-Corrosion Treatment and Repair .
17. Paint the repaired area. Refer to Basecoat/Clearcoat Paint Systems .
18. Install all of the related panels and components.
19. Connect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection .
20. Enable the SIR system. Refer to SIR Disabling and Enabling .