While prepping the engine bay, I noticed the adhesive bond between the inner fender well and fender had completely separated on both wheel wells. Since the separation was located near the valence panel attachment points, my theory is that the panel's weight and vibration, combined with adhesive shrinkage and dirt, caused the seam to separate over the years. I did see some minor separation at the edges of other seams, but when I investigated them, I found only 1/16" or less separation in most places. I suspect this was from adhesive shrinkage more than anything, and since the bonds seemed in tact, I saw no reason to "fix" them. I believe this repair to be optional, but since it was easy I went ahead and did it as part of the engine bay refurbishment.
Fender Well Adhesive Joint Repair
These pictures show the front and back of the adhesive bond. This side was worse than the driver side. At left is the adhesive pulled away from the inner fender well and the lower fender. At right is the same seam from the other side. Notice how it has pulled away from the body shell.
I used a heat gun set on low to soften the adhesive and an exacto knife to remove it in slivers. You can tell when the bond is in tact because there is no dirt discoloration on the panel and the adhesive doesn't separate cleanly. The series of pictures shows the progress. The bottom picture shows how far back I had to cut to reach a good bond.
I did similar work on the front, which needed less adhesive removed. This picture shows the entire separation with the adhesive removed and the surfaces cleaned.
To implement the repair, I used Evercoat Kittyhair. Both sides had been cleared of adhesive and prepped. I mixed up a batch and used a disposable putty knife to push the kitty hair into the crack. The fiberglass strands in the Kittyhair can make it tough to work with. I wore some nitrile gloves during this repair so I could push the Kittyhair into the seam with my fingers.
Once I was satisfied the seam was filled, I used a C-clamp to close the end gap a little and let it cure overnight.
SUMMARY: I would rate this a 2 out of 10. With a heat gun and razor it's easy to remove the old adhesive, and it's also easy to tell where the old adhesive is still bonded to the panel. Applying the new adhesive was messy, but not difficult. Be careful no to overclamp the joint. I clamped it until the Kittyhair just started to bulge. After it cured I used a heat gun, knife, and dremel sanding drum to remove stray fiberglass strands and shape the seam.