How to Repair your Plastic Bumper - Plastic Repair

Clean the repair area with a plastic solvent and press the plastic welder to the edges of the crack. When the plastic begins to soften and melt, add some filler rod and melt it into the crack, spreading the excess material around with the flat part of the welder.

The cool thing about this process is you can use a piece of the bumper you're repairing as the filler material. Cut a thin section off in an inconspicuous area and grind the paint off. You can use your bumper to fix your bumper and have no worries about mixing incompatible materials together.

You can also buy plastic filler rod in a variety of different types of plastic to suit the different types of plastics you'll encounter in your car. Many plastic welder kits will include universal plastic filler rod, too.

Plastic repair, whether you're using a two-part filler material or plastic-welding method, is meant to go on thick and be sanded down to match the contours of the panel. So don't worry if you think your repair looks sloppy-it's supposed to.

Sand the welded plastic with 80-grit, finish it up with 150, and you're ready for paint.

A less expensive repair can be done on some plastics using a two-part epoxy filler material, saving you the cost of buying a plastic welder. The prep work is similar to the welding method. We brought the munched front bumper from our Crown Victoria for the students to work on. They began by grinding off the paint and frayed plastic pieces from the repair area and cut a V-shaped groove in the tear in the bumper. Next, the students pinged the bumper by drilling a series of holes on either side of the crack at regular intervals. These holes act like rebar in cement, adding yet another place for the filler to grab onto.

Some plastics ooze chemicals that will repel paint and adhesives if not properly treated. The students thoroughly sprayed the repair area with 3M Automix 5907 adhesion-promoting spray, scrubbing the area with a Scotch-Brite pad instead of a shop towel. Then they clamped the bumper to hold it in place and applied mesh tape across the crack. This provides a substrate to hold filler material across the open areas of the crack. They filled in the backside of the crack with a rough application of filler. Once it dried, they removed the clamps to begin work on the front side of the bumper.