Moonroof repair considerations

March 1, 2021
Don't look for new moonroofs to go away. Now is the time to prepare to repair them.

If there was such thing as a controversial OEM automotive accessory, surely it would be sunroof/moonroofs. These popular windows on the world have both their dedicated fans and detractors. Some motorists will only buy a vehicle if it comes with one, treasuring the extra sunlight, ventilation and the sense of openness sunroofs/moonroofs provide. Critics point to the buildup in interior heat via these accessories when a vehicle is parked. They also criticize the extra weight, sometimes more than 200 lbs., the additional glass and motors add. Some detractors believe sunroof/moonroofs make a vehicle less safe since they break up a vehicle’s unibody construction and add significant pounds to the roof, making a vehicle more likely to rollover. 

Recently, automakers revved up the argument between the two sides by adding options for panoramic sunroofs/moonroofs, the expansive versions that replace much of the roof. Faulty panoramic moonroofs already have added fuel to the fire over safety issues with some motorists complaining about how easily the glass breaks (with some reporting the sound being similar to an explosion). A few OEMS have already issued recalls.  

But don’t look for these new moonroofs to go away. They’ve proved very popular, and OEMs stress they are addressing quality and safety concerns.  

Now is the time to prepare to repair them. The following instructions from GM describe both how to complete some of the most common repairs on these accessories, along with roofs featuring them.  

A note on nomenclature 

What exactly is the difference between a sunroof and a moonroof. At one time, a sunroof was either a small glass roof or a roof that could be manually opened while a moonroof was the motorized version. These definitions don’t mean much anymore. Some OEMs call all their versions sunroofs while others stick to the term moonroof. When it’s time to perform repairs, you’ll need to be familiar with what each automaker prefers when you do research. 

Repair Steps  

Sunroof Housing Replacement – 2021 Chevrolet Blazer  

Removal Procedure  

  1. Remove the Headlining Trim Panel using GM’s Headlining Trim Panel Replacement document. 

  2. Remove the Inner Sunroof Window Seal using GM’sSunroof Window Seal Replacement - Innerdocument. 

  3. Remove the Sunroof Window using GM’sSunroof Window Replacement document. 

  4. Remove the Roof Stationary Window using GM’sRoof Stationary Window Replacement document. 

  5. Remove both sunroof housing front drain hoses from the sunroof housing front drain hose spigot. 

  6. Remove both sunroof housing rear drain hoses from the sunroof housing rear drain hose spigot. 

  7. Disconnect the electrical connectors. 

  8. Remove the Outer Sunroof Window Seal using GM’sOuter Sunroof Window Seal Replacement document. 

  9. Remove the Sunroof Module Bolt. 

  10. Remove the Sunroof Housing. 

  11. Transfer components as necessary.    

Installation Procedure 

  1. Install the Sunroof Housing. Caution: Refer to GM’sFastener Caution document. 

  2. Bolt the Sunroof Module Bolt. Install and tighten at9 Y (80 lb in 

  3. Install the Outer Sunroof Window Seal using GM’sOuter Sunroof Window Seal Replacement document. 

  4. Install both sunroof housing front drain hoses to the sunroof housing front drain hose spigot. 

  5. Install both sunroof housing rear drain hoses to the sunroof housing rear drain hose spigot. 

  6. Connect the electrical connectors  

  7. Install the Roof Stationary Window using GM’sRoof Stationary Window Replacement document. 

  8. Install the Sunroof Window using GM’sSunroof Window Replacement document. 

  9. Install the Inner Sunroof Window Seal using GM’s Sunroof Window Seal Replacement - Inner instructions document. 

  10. Install the Headlining Trim Panel using GM’sHeadlining Trim Panel Replacement document. 

  11. Perform the necessary initialization procedure using GM’sSunroof/Sunshade Motor Initialization document. 

Sunroof Sunshade Motor Replacement - 2021 Chevrolet Blazer 

Removal Procedure  

  • Place the sunshade in the full-open position. Note: It is only necessary to lower the headlining. Only do those steps in the headlining procedure that will allow access to the component being removed.  

  • Remove the Headlining Trim Panel using GM’sHeadlining Trim Panel Replacement document.
  • Insert a 4 mm hex wrench into the motor pinion gear hex feature.  

  • Turn the hex wrench until the sunshade torsion tube locking window hole is in the 12 O’clock position. 

  • Insert a locking pin all the way through the sunshade torsion tube to hold the sunshade inplace. Disconnect theElectrical Connector.

  • Remove the Sunroof Sunshade Motor Bolt. 

  • Remove the Sunroof Sunshade  

  • Installation Procedure   

    1. Place sunroof sunshade motor to the sunroof sunshade motor bracket. Caution: Refer to GM’sFastener Caution document. 

    2. Bolt the Sunroof Sunshade Motor. Install and tighten [3x] 4 Y (35 lb in). 

    3. Connect the Electrical Connector. 

    4. Remove the locking pin from the sunshade torsion tube that is holding the sunshade in place.  

    5. Ensure that the sunroof sunshade and window operate properly. Refer to GM’s Sunroof Motor/Actuator Initialization/Teach Process document. 

    6. Install the Headlining Trim Panel using GM’sHeadlining Trim Panel Replacement document. 

    7. Ensure that the sunroof sunshade and window operate properly.  

    Roof Outer Panel Replacement (With Sunroof) 2021 Cadillac CT5  

    Materials 

    • Structure Adhesive. See GM’sMetal Panel Bonding document.  

    • Windshield Urethane 

    Removal Procedure  

    Warning: Refer to the following GM documents: 

    • Approved Equipment for Collision Repair Warning 

    • Collision Sectioning Warning 

    • Glass and Sheet Metal Handling Warning 

    Note: The roof outer panel is mild steel. Refer to GM’sMild Steel document. 

    Note: Refer to GM’sCollision Repair Specifications document.  

    1. Disable the SIR system. Refer to GM’sSIR Disabling and Enabling document. 

    2. Disconnect the battery negative cable. See GM’s Battery Negative Cable Disconnection and Connection document. 

    3. Remove all related panels and components.  

    4. Remove the sealers and anti-corrosion materials from the repair area as necessary. See GM’sAnti-Corrosion Treatment and Repair document. Note: Do not damage or cut attaching panels and reinforcements.  

    5. Remove spot welds from roof outer panel. Note: Do not damage or cut attaching panels and reinforcements. 

    6. Remove all spot welds from roof outer panel.  

    7. Apply heat to shaded area to release structural adhesive from roof outer panel.  

    8. Using a suitable tool cut the urethane to release roof panel from the body structure. Note: Do not damage or cut attaching panels and reinforcements.  Note: All cuts are square to surface.  

    9. Cut the roof outer panel at the marked location.  

    10. Remove roof outer panel from the vehicle.  

    11. Using a die grinder with a cut off wheel or equivalent tool, remove the remaining portion of the roof and the laser weld joint from both sides of the vehicle. 

    12. Remove remaining structural adhesive from vehicle.  

    13. Remove all remaining loose Anti-Flutter from the roof headers and bows.  

    Installation Procedure   

    1. Position the roof outer panel on vehicle using 3-dimensional measuring equipment.  

    2. Verify fit of roof outer panel to roof headers and bows. Repair as necessary. Temporarily remove roof outer panel.  

    3. Prepare all mating surfaces for welding as necessary.  

    4. Apply GM-approved Weld-Thru Coating or equivalent to all mating surfaces. See GM’s Anti-Corrosion Treatment and Repair document. 

    5. Apply Anti-Flutter to headers and bows as necessary. Note: Only remove E-coat where adhesive will be applied. 

    6. Clean and prepare roof outer panel and vehicle for adhesive according to adhesive manufacturer’s recommendations. Refer to GM’s Metal Panel Bonding document. 

    7. Apply structural adhesive on the mating surfaces of roof outer panel and vehicle according to adhesive manufacturer’s recommendations. See GM’s Metal Panel Bonding document. 

    8. Remove E-coat where windshield urethane will be applied. Refer to urethane manufactures preparation instructions.  

    9. Apply a 12 mm (1/2 in) bead of the windshield urethane to the mating surface of the body side panels. Refer to urethane manufactures preparation instructions.  

    10. Apply a 12 mm (1/2 in) bead of the windshield urethane to the roof reinforcements. Refer to urethane manufactures preparation instructions. 

    11. Apply a 12 mm (1/2 in) bead of the windshield urethane to the roof front header. Refer to urethane manufactures preparation instructions. 

    12. Install roof outer panel to vehicle and clamp into place.  

    13. Install spot welds on roof outer panel.  

    14. Install all related panels and components.  

    15. Apply the sealers and anti-corrosion materials to the repair area as necessary, referring to GM’sAnti-Corrosion Treatment and Repair documentNote: Before refinishing, refer to GM’sAnti-Corrosion Treatment and Repair document. 

    16. Paint the repaired area. See GM’sBasecoat/Clearcoat Paint Systems document. 

    17. Connect the battery negative cable. See GM’sBattery Negative Cable Disconnection and Connection document. 

    18. Enable the SIR System. See GM’s SIR Disabling and Enabling document. 

    About the Author

    Tim Sramcik

    Tim Sramcik began writing for ABRN over 20 years ago. He has produced numerous news, technical and feature articles covering virtually every aspect of the collision repair market. In 2004, the American Society of Business Publication Editors recognized his work with two awards. Srmcik also has written extensively for Motor Age and Aftermarket Business. Connect with Sramcik on LinkedIn and see more of his work on Muck Rack. 

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