Rattle Noise from Upper Intake Manifold Cover - keywords 5.3 accel accelerate alignment bolt buzz cap compartment cowl HVAC idle LMG rear stud vibration

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

A dealer may encounter a rattle noise that can be heard in the passenger compartment. The rattle noise may be heard during acceleration or at idle.

The Upper Intake Manifold Cover may be contacting a HVAC module retaining stud.

Complete a GMVIS and check the last 8 digits of the VIN number. A updated Upper Intake Manifold Cover has been installed on all vehicles built after the VIN break point of 7R101807. If the vehicle was built after the VIN of 7R101807 the cover should not make contact the HVAC module retaining stud.

If the vehicle was built before the VIN break point of 7R101807, inspect the Upper Intake Manifold Cover.

The Upper Intake Manifold Cover is attached to the rear of the intake manifold. (See SI repair procedures for Upper Intake Manifold Cover Replacement) There is a HVAC module retaining stud that protrudes from the cowl directly behind the Upper Intake Manifold cover. It is possible for this cover to hit the HVAC module retaining stud, and induce a rattle noise heard in the passenger compartment.

Remove the Upper Intake Manifold Sight Shield and retaining bracket using SI procedures for Upper Intake Manifold Sight Shield Replacement. Locate and make a mark on the Upper Intake Manifold Cover where the HVAC stud touches the cover. Reposition the Upper Intake Manifold Cover so the upper right corner of the cover can be accessed. (refer to #1 on illustration below) The intake manifold does not need to be removed to complete this repair. To repair this concern a one inch / 30 M/M hole will be drilled in the area of contact. After the area to be drilled can be accessed, pull back the Upper Intake Manifold Cover acoustic foam (on the inside or front of the cover) so that the cover can be drilled. Be careful to drill this hole directly where contact between the HVAC stud and cover have occurred. Push the acoustic foam back into place after drilling the 1" hole and reinstall the cover back to its proper position on the rear of the intake manifold. There may also be a plastic cap covering the threads of the HVAC retaining stud that was touching the Upper Intake Manifold cover. If there is a plastic cap on the HVAC retaining stud, remove the cap and discard it during the repair. Make sure the HVAC stud no longer touches the cover and evaluate the rattle.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.