Hardtop Water Leak into the Rear Compartment Area

When servicing the vehicle with the VIN you entered, the following diagnosis might be helpful if the vehicle exhibits the described symptoms.

The customer may complain of water in the rear compartment area behind the seats or even under the seats. Water may be dripping from either ends of the garnish molding under the rear window. The actual entry point is the seam where the rear edge of the hardtop is sealed to the body tub flange.

The possible leak paths can be better understood using the following SI documents:

1. # 842633 "Roof Description"
2. # 844927 "Hardtop Replacement Procedure"
3. # 657292 "Quarter Panel Replacement - Rear Hardtop" Step 22 quarter cutaway illustration.

The rear window garnish molding (SI Document Number 656014) and the rear compartment front side trim panels (SI Document Number 656914) should be removed (if this has not already been done). This will reveal the entire "seam" where the hardtop meets the tub as well as the "cups" referenced below.

The following are 2 likely leak path descriptions/corrections.

1. Water entering anywhere along the seam where the hardtop ditch (or U - channel) meets the tub flange. The assembly plant runs bead of butyl sealer across the hard top ditch (or U - channel) before it is set down onto the tub flange. This sealer bead is approximately 25.4 mm (1 inch) forward of the SMC structural adhesive bead (on rear top flange) that contacts the tub shelf . It runs across the back (below the rear glass) and wraps onto each quarter panel. A void in this sealer will also allow water to enter the vehicle, but should be easily seen from inside the passenger compartment with the garnish molding removed (per above). Any voids must be resealed using urethane sealer. As an added measure when addressing larger voids, urethane can be applied and then thumb grade (clay type material) used on top to push the urethane further into the void.
2. Water dripping from the holes in the bottom of the 2 "cup" structures. The hardtop is made of 2 SMC (Sheet Molded Compound) panels bonded together. Reference the quarter section cutaway in step 22 of SI Document Number 657292. The 2 SMC panels are bonded slightly inward of the actual hardtop edge formed by the panels. At this outer edge, there is a small gap that runs the full length of the edge (cross car, forward of rubber deck lid seal). This edge is virtually impossible to see, especially where it runs forward of the deck lid seal. A small mirror can be used at the outer most rear edges (with the deck lid open) to obtain some view of the gap. If the run channel is filled to the point of overflowing, water will pass through this gap and find any voids that may be present in the SMC panel bond. If a void is present, water will enter and work its way to the lowest point in the hard top structure which may be one or both cups referenced above. Although the gap across the vehicle (forward of decklid) differs slightly from the quarter panel area (illustration referenced above), the leak potential is the same. Remove the rubber trunk seal (for some clearance) and apply urethane sealer as neatly as possible to the underside of the hardtop rear edge. If this does not correct the leak, the quarter panels will have to be removed (SI Document Number 657292), and the gap in that area sealed as well. Any excess sealer should be wiped away using an alcohol dampened rag.

Additional information:

SMC structural adhesive is also used across the front windshield header and the hydro formed roof bow. Urethane sealer is also used in the B - Pillar area. Ref SI2K docs mentioned above for more detail. Sealer - contact Kent Industries 1-800-654-6333, "Leak Seal" part number 10570. Bond - contact Specialty Products 1-248-391-6300, "Beta Seal" part number 57502.

Please follow this diagnosis 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. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. This diagnostic approach was developed for the vehicle with the VIN you entered and should not be automatically be used for other vehicles with similar symptoms.