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Repairing blow molded plastic bumpers

Monday, November 28, 2016 - 09:00
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In 2007 Jeep and its supplier, ABC Group, were recognized by the Society of Plastic Engineers for incorporating blow molded textured plastic bumpers on the JK-series Jeep Wrangler. These blow molded bumpers replaced Jeep’s long running rolled formed steel bumpers. Replacing the steel bumper with a blow molded plastic bumper offered a 12 percent reduction on piece cost and assembly cost, as well as a 9 percent weight reduction, compared to the previous steel bumper.                                                                                                                                                                                                                        

Blow molded parts are nothing new to the automotive industry. However, using this blow mold process to make a plastic bumper is new. And it might seem somewhat challenging to repair and remove a dent from a bumper like this, since you can’t push a dent from the backside. Luckily these bumpers are hollow, and depending on how severe the damage is, it’s actually not that difficult if you have the right tools and equipment.

This Jeep Wrangler blow molded bumper has suffered a deep dent in the corner. To push the dent out, an access hole will have to be cut on the backside.

                                                                                                                                                                                                                                   Before repairing any part, clean the bumper before starting the repair process. Washing molded-in-color textured plastic bumpers is more important than normal because they are made of raw TPO plastic and people often use silicone-based products to restore the shine. It is important to wash with soap and water two or three times, allow to dry, and clean again with a solvent based plastic cleaner to ensure the bumper is free of any contaminates.


The key to removing a dent in a blow molded bumper is to cut an access hole on the backside. The removed panel will be welded back in to seal the bumper after the dent is pushed out. Depending on where the dent is on the bumper, it may be difficult to access from the backside where the bumper mounts, for example. Before you decide to attempt the repair, make sure you have clear access to the back of the dent in the area you plan to cut the access hole.

Cut a hole on the backside to allow access to push the dent out from the back.

If you want to attempt the repair, cut the access hole on the backside large enough to give you complete access to the back of the dent. Mark where you will cut the hole on the back of the bumper with a marker, then carefully cut it out with either a jigsaw or a sharp utility knife. Reserve the removed access panel for reattachment later on.  After you cut the hole, reach in with your pushing tool to make sure you can access all angles before heating the part. Cut the hole bigger if needed. 

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