Fender Liner Flange Repair

Many bumpers have a flange about an inch inside the wheel well where the inner fender liner mounts. This feature sticks out vertically from the bumper face and often tears right at the base, where the plastic is thinnest. Because of the 90 degree angle and the thin plastic at the base, this would be hard to repair with an adhesive. But using Polyvance’s nitrogen plastic welder and our 90 degree angle welding rod, this is a quick and easy repair. In this video, we’ll be doing a one-sided repair that will not affect the appearance of the bumper on the other side.

Click here to see an overview of the nitrogen welding process. Click here to see all of our nitrogen plastic welding videos.

Always wear proper safety gear while working!

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Click here: https://www.youtube.com/watch?v=KbLrrkaXNKo

Products Used:

Note: This is a list of the Polyvance products that can be used to make this repair. This list does not include sanders, grinders, or other common tools you will need. If you have any questions, please don't hesitate to call technical support at 800-633-3047.

• 1000 Super Prep Plastic Cleaner (several options available) OR 1001-4 EcoPrep Plastic Cleaner
• Aluminum Body Tape (several options available)
• 6125 Tapered Burr
• Nitrogen Plastic Welder (several options available)
• We used the R02-08-03-BK black polypropylene corner welding rod for this repair.
  View all of our welding rod here.

Video Notes:

• English Closed Captions have been provided for this video. Click on the CC button to turn them on or off.
• The length of this video is in no way representative of the actual time required to perform a complete repair and therefore should not be used for estimating purposes.

Music Credits:

• "Sage" by Slenderbeats
  From the YouTube Audio Library

English Transcript:

Many bumpers have a flange about an inch inside the wheel well where the inner fender liner mounts. This feature sticks out vertically from the bumper face and often tears right at the base, where the plastic is thinnest. Because of the 90 degree angle and the thin plastic at the base, this would be hard to repair with an adhesive. But using Polyvance’s nitrogen plastic welder and our 90 degree angle welding rod, this is a quick and easy repair.

Torn fender liner mount flanges can be easily and quickly repaired with Polyvance’s nitrogen plastic welder and the R02-08 corner welding rod. We’ll be doing a one-sided repair that will not affect the appearance of the bumper on the other side.

As with any plastic repair, thoroughly clean the plastic before you start sanding or grinding on it. Use soap and water to get any heavy dirt off the back, then use one of Polyvance’s plastic cleaning solutions to remove any oil-based contamination. Spray a heavy, wet coat, then wipe off with a clean paper towel.

We are going to be welding on the forward side of the flange so that the repair won’t be visible when the fender liner is installed. To prep the surfaces for welding, use some 80 grit sandpaper by hand to remove any paint overspray from the area and to rough up the plastic. Blow the area dust free when you are done.

To accurately position the flange, hold the flange in place with one hand, then melt a small tack weld with the tip of the airless plastic welder at the tear. Melt in a tack weld every inch or so to temporarily hold the flange in the proper position.

After allowing the tack welds to cool, gently apply aluminum tape to the opposite side to hold the flange in place while you make your weld. Use one of Polyvance’s heavy duty three mil thick tapes, which are much stronger and stickier than common air conditioner duct tape. Use a body spreader or other tool to apply the tape tightly to the flange so that the plastic doesn’t blow through when it’s welded from the other side. This flange has a channel at the bottom and is paper thin, so a strong backing of aluminum tape is essential for a proper repair.

Now that the flange is securely in position, use Polyvance’s 6125 tapered die grinding burr to slightly v-groove the area where the welding rod will go. This will allow for a flush, nearly invisible repair.

Using Polyvance’s polypropylene R02-08 corner welding rod and the nitrogen plastic welder, weld into the corner where the flange meets the bumper face. Focus the heat at about a 45 degree angle so both the rod and the bumper are melted at the same time. The corner rod is a little trickier to use than our other profiles. It helps to focus the heat a little higher up on the rod and to make sure you heat both legs equally so the rod falls down straight and doesn’t wander from side to side. Also, make sure you melt the surface of the bumper, but don’t keep the heat on it too long… you don’t want to overheat the bumper and cause any distortion on the outer face.

When you are finished laying down the one pass of R02-08 corner welding rod, go back and smooth the weld with the airless plastic welder. This is an optional step in case the appearance of the weld doesn’t meet with your satisfaction. Reheat a 2 inch section with the nitrogen welder, then smooth that area with the airless welder at maximum temperature. Repeat this process until the entire welded area has been smoothed.

Allow the weld to cool completely, then peel off the aluminum tape. Because the R02-08 corner welding rod is actually thicker than the original plastic, the repaired area should be as strong or stronger than the original. Test the strength by pulling straight out using a pair of pliers, as you see here. The flange only has to hold the inner fender liner in place, so this is plenty strong to get the job done.

Also notice that there is no distortion of the plastic or the paint on the outside, so no cosmetic work needs to be done on the bumper. Again, to achieve this result, minimize the input of heat into the bumper during the welding process by speeding up your pass and focusing more heat on the rod.

This repair is another example of how a Polyvance nitrogen plastic welder can help keep labor dollars in the shop and keep another plastic bumper out of the landfill. Polyvance has a full range of products and equipment to repair and refinish automotive plastic parts. Get more info at www.polyvance.com, or call us toll-free at 800-633-3047.