Plastic repair GURUS since 1981
June 07, 2016 by Polyvance
In 2007, Jeep won an award from Plastics Technology Magazine for its groundbreaking use of blow-molding on Jeep Wrangler Bumpers. Though innovative, blow-molded bumpers are thought by some to be impossible to repair, due to the fact that dents cannot be reached from the back.
Thanks to Polyvance’s master technician, John Wilburn, we’ve discovered a simple repair technique that can alleviate the need to spend a small fortune on brand new Jeep Wrangler bumpers.
STEP ONE: Using a paint marker, draw a square on the backside of the bumper, relative to the dent on the front. Notch out and remove the square. From here, we can clearly see and access the dent for the repair.
STEP TWO: Using a heat gun, like Polyvance’s 6500 VT, heat the dent, as well as the area four to six inches around it. This heat will release the pressure in the dent, allowing us to manipulate it later. You only want to heat the plastic, so be sure to keep the heat gun in a constant, circular motion to prevent anything from melting. You’ll want the plastic to be just hot enough for you to be able to touch for two to three seconds.
STEP THREE: Once the plastic has been heated, access the dent through the hole in the back of the bumper. Using a wooden stick, or other blunt object, carefully push the dent forward until it releases. You may still have high or low spots. If that is the case, repeat the process of heating and manipulating the plastic until you are satisfied with the general shape of the repair area. It does not have to be perfect yet. You may need to push up and down simultaneously, as you can see us doing here, if you have high and low spots side by side.
STEP FOUR: Once the bumper cools, sand the damaged area with 80-grit sandpaper. Once this is done, you’ll be able to definitively see the remaining high and low spots. Repeat the process of heating and pushing until the finer points of the dent have been removed.
STEP FIVE: Sand your repair area again with 80-grit sandpaper, more thoroughly than before. You may continue to discover spots, as we did, that need additional attention. If that is the case, repeat the process of heating and pushing before you move on.
STEP SIX: Now, using 180-grit sandpaper, remove the fuzz left over from the 80-grit. Then, using 180-grit paper again, roughly sand six to eight inches around the repair area by hand so that any paint overspray will stick to the bumper.
STEP SEVEN: Apply Polyvance’s 1050-A Plastic Magic Adhesion Promoter, following the instructions on the label.
STEP EIGHT: Apply primer, allow to dry, and block sand using 320-grit sandpaper. Repeat this process until you reach the desired appearance.; as many as three or four times.
STEP NINE: Finally, it’s time to plug the hole that was cut out in step one. If necessary, shave the sides of the plug so that it can easily fit back into the hole. Apply Polyvance’s aluminum tape to the inside of the bumper, and then place the plug on top.
STEP TEN: Grind off the paint and etch the surface of the plastic to prepare for welding. Using an airless plastic welder, tack-weld at random points along the perimeter of the plug.
STEP ELEVEN: Using a 6125 Tapered Burr, V-Groove along the perimeter of the plug. Then, using one of Polyvance’s Nitrogen Plastic Welders, weld a pass of plastic, most likely polypropylene, as shown here, into the V-Groove. Finally, flatten the welded area using a combination of the nitrogen and airless plastic welders. Since this part of the repair will be unseen, it does not have to look flawless.
As you can see, this repair technique provides a quality repair that can eliminate the need to buy expensive replacement Jeep bumpers.