-some people say you can use suction cups or a plunger to pull the dent. I couldn't make it work in this case, but it's easy and worth a try.
-if you can get behind the dent, you may be able to push it out
-You should try to pull the dent as soon as possible. If you wait too long, there will still be a trace of the dent when you pull it. Plastic creeps when it's under stress for a long time.
-if you use a ceramic flower pot for this, you might break it
-you may scratch the paint a little if you're not careful enough
-I imagine this process works on metal too, but I haven't tried it.
Step 1: Tools and Materials
Tools and Materials:
-vacuum cleaner (ordinary household may work, or a shop vac, use the strongest one available)
-tape (duct tape or masking tape)
- flower pot or bucket with hole in the bottom. The stiffer the better, and large enough to cover the dent. If there's more than one hole, you can tape over the other holes.
-soapy water in a bucket
-towel you don't care about
Step 2: Clean Off Dirt
You'll want the tape to stick well, so clean off the edge of the pot and the car where the tape will go. After cleaning, dry off with a towel so tape will stick. You might want to apply tape to the edge of the pot to prevent scratching the car's paint.
Step 3: Tape the Pot in Place
Step 4: Pull!
If you're lucky, the dent is now gone.
Step 5: What If the Dent Is Still There?
If you can get your hand behind the dent, you may be able to push hard enough to help the dent pop out. I was about to give up when I tried this, and then it worked. On the Honda, the seam shown can be snapped open and you can stick your hand behind the dent. It's pretty awkward or perhaps I wouldn't have needed the vacuum.
If it still doesn't work, you might try a larger pot or a different vacuum cleaner, or double check to see that your tape nearly seals or completely seals the pot onto the bumper cover.
If THAT doesn't work, you may need a vacuum pump. The following is speculative. I've used vacuum pumps to do a bunch of weird things, but not this. Fortunately, if you don't have a regular vacuum pump, you have a very large one on hand if your car's engine runs. And manifold vacuum at idle can be quite strong! However, I haven't checked into the details of how to apply manifold vacuum where you want it. And you might want to use some kind of filter to keep your engine from swallowing crud. If you are using a vacuum pump of some sort, you must seal the pot on very well. You may need to use a plastic pot or seal a ceramic pot with a plastic bag. However, if you do this it will pull out almost any dent unless it's quite small. For instance, let's say you have a dent 10 inches in diameter and, with some leaks, you can still pull 15 inches Hg. (about half an atmosphere). That's more than 500 pounds of force! It may help to use a vacuum gauge so you can tell if you are getting a pretty good vacuum or if you still need to seal some leaks.
Step 6: Clean Up and You're Done (unless the Paint Cracked)
This is not really an after picture, it's just a picture of a Honda. The color is about right, though. In real life there was a little flat spot that remained because it had taken us a month to get around to pulling the dent. Plus the paint was scratched from the original incident.
10 cent solutions to million dollar problems. And vice versa.