Mustang MonthlyHow To Paint Body
Post-Paint Detailing: Undercoat Wheelwells the Right Way
Undercoating wheel wells to the correct factory texture
It was a bummer, but when we had our 1965 Mustang painted the painter neglected to mask off the wheelwells, so Poppy Red paint drifted onto the old undercoating. That’s not uncommon with any paint job, and final assembly usually always includes touchup detailing over any overspray, including in the wheelwells. You’d be surprised how Poppy Red overspray is visible in an otherwise black wheelwells, even with the wheels bolted up and the car on the ground at ride height.
Our car’s post-paint wheelwells weren’t really that bad when it came to overspray—“almost flawless” in painter Jason White’s opinion—but they still needed to be detailed to make them look right. Simply painting over the overspray will not duplicate the factory procedure and look however—the factory undercoating has a brownish color, whereas the newer undercoating we’re spraying in this story is a very dark brown that looks black inside the wheel well. It will, however, lighten up and turn a little browner with age and road miles. Since we were not doing a concours restoration to the undercarriage, Jason White masked off the axle, but left the gas tank exposed, same as dealer procedure. The factory, of course, applied sound deadener prior to installation of the gas tank. Dealers applied undercoating, which is not the same material as factory sound deadener.
Therefore, Jason White sprayed on a new layer of undercoating, as seen here, to the passenger side rear wheelwells. The procedure is the same for the other three wheelwells, but you should make sure to coat the tops of the inner side of the front fenders as well, to avoid stone chips and “stars” in the paint from errant road debris.
01. After pressure washing and cleaning, use a Scotchbrite pad on the old undercoating to remove any loose debris.
02. Mask off the fender, rear axle, brakes, and leaf springs.
03. Blow off loose undercoating flakes with compressed air.
04. Jason White sprayed 3M No Cleanup High Coverage Body Schutz Coating, utilizing a supplied plastic adaptor connected to a “sludge gun.” Both products are readily available at paint and bodyshop supply stores.
05. With a 3-4 psi setting, the sludge gun sprays the coating to a coarse, factory-like texture. A higher pressure setting would spray finer particles for a smoother finish, unlike factory. The lower the air pressure, the better for coarse texture. White holds the gun at a reasonable distance so that particles create a splattered factory look and the coating “builds higher.”
06. Be sure to coat the top inside of the fenders for protection from flying rocks.
07. Pull off the masking paper.
08. The coating splattered onto the gas tank, which is dealer procedure. The factory applied their sound deadener to wheel wells before the gas tank was installed.
09. Our light undercoating is on top of the original undercoating. Spray it with water and put a few miles on the car, and it will eventually turn a lighter shade of brown.