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My wife's brand new bumper cracked from some road debris (image):

enter image description here

Body shop quoted her something ridiculous like $1100 (a $280 part plus a ton of labor, to replace the whole thing). I know there are adhesive patch kits out there. I'm guessing most body shops won't want to waste their time for such an easy repair like that, that they won't get rich off of. I'm fairly handy, I've laid up custom fiberglass projects in the distant past... should I try some sort of self repair like this? I mean, especially if we were considering replacing the whole thing, there's nothing to lose at this point. Painting seems like the one thing I wouldn't be able to do a great job at, but there's really no paint damage, I feel like if I could patch this from the inside securely, all there would be is a barely visible line where the crack was. But I'm not sure how hard it will be with the location of the crack in a corner like this. Car is a 2016 Subaru Impreza if it matters.

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    Sorry, not an answer but I just wanted to share an experience I had so you don't make the same mistake I did: if you need to use filler get one that is specially for plastic parts. I didn't know there was a difference and used normal filler. It cracked over time as the bumper flexed and expanded/contracted with temperature. I've had to start again. (Also, have you tried a wreckers?) – MeltingDog Aug 26 '16 at 2:34
  • It's may or may not be important to note there is no scale or reference in this picture. i have no experience repairing bumpers but I would imagine a 1" crack is much easier to repair than a 1' crack - being somewhat familair with the 2016 Impreza, it looks like this crack is only a couple inches long. – MooseLucifer Aug 26 '16 at 14:32
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Sounds like you have the right idea, at least for a temporary repair. You'll have to remove the entire bumber assembly to do this right, and you'll need to go slow as to not break the platic clips and geegaws that hold the whole thing together like a jigsaw puzzle.

Because of the special poyurethane type polymers that are used in these bumpers, one challenge is getting anything to bond to these surfaces. Regular fiberglass resin isn't going to hold well for long.

Clean and rough up the inner surface with 160 grit all around the crack. One goo you might try which I've have good luck with is called "Plastic Welder", and it is a two-component adhesive that mixes and sets up quickly.

It will work best if you can temporaily clamp the crack perfectly closed from the outside. I'd start by trying good duct tape.

Any fiberglass mat will do; I would apply a "buttering" layer of whatever adhesive you decide, and no sense being spare. Press in your reinforcement mat, you can probably use a standard fiberglass roller for this.

Google for "bumper repair adhesive" and you can probably find some appropriate goo that is specifically designed for this application. I prefer two-component types, I think these work better, and have the plus of catalyzing quickly when you need it, rather than waiting forever for a long cure.

Here's a 3M product with a good reputation

  • Great answer, I would use zip ties before using fibreglass. You can trim the ties on the visible side. I actually used this method when I needed a replacement bumper that was very rare/expensive. I bought two accident damage ones (one was damaged on the left, other damaged on the right), cut them in half and zip tied and fibreglassed them together. Of course lots of filler and sanding afterward to a perfect finish. – DizzyFool Aug 26 '16 at 12:49
  • You could also use a "hot stapler" for improving the stability of the repair. Melt in the staples from the non-visible side – Martin Aug 26 '16 at 13:01
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There are companies that specialize in doing this sort of repair. Many are mobile and can repair it in your driveway. A Google search of "plastic bumper repair" of the Bay area showed a listing for a company called "Dent Crew". They specialize in paintless dent and plastic bumper repair. This is not an endorsement for this particular company but an example to let you know the technology is out there. Most of the time the repair typically involves welding the defect with a plastic filler. Repainting is required for cosmetic purposes.

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