Repairing a split in a plastic bumper can be done at home if you want to avoid the expense of an auto bodyworks garage repair bill, or you do not want to replace the whole bumper. You can repair the split with epoxy or bumper adhesive. Both filler products use the same installation instructions. The key to a high quality repair job is proper sanding. The more you sand the bumper smooth, the less visible the repair will be.
Grind the split into a wedge shape on the side of the bumper with an orbital sander. Grind the split down until it is about three times larger than the original split. You can also use a hacksaw to cut the wedge shape.
Sand the split area with 80-grit sandpaper until the bumper is completely smooth. Wipe the surface of the bumper with a soft cloth to remove plastic dust and residue. Follow this with a coating of plastic cleaner.
Spray the surface of the wedge in the bumper with adhesion promoter to help the filler adhere to the bumper and meld with the plastic surface.
Sand the area once more with the orbital sander and 80-grit sandpaper to remove excess plastic.
Clean the bumper with plastic cleaner and add another coating of adhesion promoter to the bumper.
Place several small sheets of reinforcing mesh over the damaged area in the bumper. Coat the mesh with repair epoxy. Use a plastic spreader to apply the epoxy over the mesh. Apply a second coat of epoxy once the first coat is no longer tacky. Allow the epoxy to dry for two hours.
Sand the epoxy with the orbital sander until smooth. Sand with 80-grit then 120-grit sandpaper.
Apply a finishing putty with the plastic scraper then sand it by hand with the 120-grit sandpaper once the putty dries.
Prime the surface of the bumper after 24 hours. Allow the primer to dry for two hours then apply two coats of bumper paint, allowing each coat to dry for one hour.