Dented and damaged bumpers can detract from the appearance, and value, of your car. As of 2009, a damaged bumper cost about $700 to fix. Tears and cracks are some of the worst damages that a bumper can experience. You can, however, fix all of those problems by yourself with a little time and energy.
For small scratches or dings, according to meguiarsonline.com, you'll need to either fill the scratch in or sand down the paint until the scratch is no longer noticeable. You then can paint over the sanded areas with a paint repair kit—add paint to the scratch or ding, letting it dry between layers, until it is completely filled in. Then, sand it with 1000 grit sandpaper, then 2500 sandpaper, then polish it. That will help ensure that the paint is even with the rest of the bumper, and the damage is not noticeable.
According to popularmechanics.com, to fix heavy damage, you must first find the screws or tabs that hold the bumper, or facsia, in place, and undo or unhook them. Scuff the fascia with sandpaper and then clean it with plastic surface cleaner. For a tear, make sure both the inside and outside are clean. Rinse and let dry, then wipe with a preparatory solvent. Let it dry, then sand with 80 grit sandpaper.
Cut a V shaped groove in the front and back pieces with either a sander or a drill and rotary file. For all repairs, starting with the back, fix any cuts or tears with self-stick fiberglass repair tape. Mix up a body repair adhesive and apply it over the tape with a repair squeegee. Do that step twice. Then, do the same for the front.
After the adhesive hardens, remove the tape, starting with the front. Sand it down. Fill the cut, tear, dent or scratch with the correct repair material for your plastic bumper, and squeegee to level it. Let it dry, then sand again with sandpaper from 80 grit to 120 grit. Repeat, then sand one more time with 400 grit sandpaper to prepare for painting.
To paint, first use two coats of sealer. Prime the fascia with two coats of primer. Sand with 400 grit paper, then wetsand it before applying a base coat. Wipe with a wet cloth to get rid of all the dust and sand. Spray with the basecoat; you may need more than one coat. Mix a clearcoat with a hardener solution, then use two coats. After that dries, wetsand it again. Use a rotary machine and a rubbing solution to bring out the luster of the paint. For shine, use a rotary machine and a polishing solution.
According to "How To Repair and Restore Bodywork" by David Jacobs, light damage to metal bumpers, such as dents and bends, can be hammered out. If, however, the metal bumper is torn or cracked, it cannot be repaired and must be replaced.