Bought an '06 Big horn last week and the previous owner had damaged the front Air Dam/Valance. Here's a couple shots after I tried to straighten it out by hand.
You can see that even after trying to align the tear it was still off the mark & although not terribly visible, It still bothers me so I had some Mar-Hyde laying around & thought I'd give it a shot to see if I could clean it up until I could replace the Air Dam.
These are the tools I would use:
First things first. Clean the area & about 6" around with plain old soap & water.
Back side too
After that I wiped both sides down with adhesive remover to eliminate road grime & help with adhesion.
Then, I very carefully used the heat gun to warm up the Air Dam until I could re-align both halves. I made sure to do this very slowly and worked the warm plastic until I was satisfied with the alignment
Once aligned, i scuffed the backside of the piece with medium Scotch Brite to help the give the Mar-Hyde something to bite into.
I didn't want the adhesive to bleed through the crack & make it more noticeable than absolutely necessary, so I cut a few pieces of aluminum tape to enclose the exterior & prohibit the Mar-Hyde from coming all the way through the tear.
Okay, so the tear is all cleaned, degreased, aligned & scuffed, then the exterior was covered tightly with aluminum tape. Time to mix the adhesive. I used Nitrile gloves while working this stuff as the label says it's highly irritant.
For application I actually ended up skipping the putty knife & used an old expired debit card. It was actually the perfect size to negotiate behind the Air Dam while still on the truck & flexible to boot. It worked extremely well. I put a nice, thick application on the back of the tear, being mindful to work it between the surfaces but not enough to seep through to the front where it would be visible.
After allowing the Mar-hyde to set, I removed the aluminum tape. The Mar-hyde sets to a light gray color, so i masked off the mended tear as close as I could and used a fine brush & semi gloss black vinyl dye and covered the gray with a couple fine coats.
After allowing the paint to dry, I pulled the masking tape off to check my work. I'n my opinion, it's a serviceable repair which is hard to spot from a very short distance. It will hold me over until a replacement can be had.
Here's a shot at approx 12"
Here's another at approx 3'
And finally, at approx 5'
All things considered, I'm pretty pleased with the results. If I didn't know it was there & know exactly just where to look, I'm sure I would have been hard pressed to notice the repaired tear. Looks tons better & will hold me over until my OCD forces me to replace it.