This Instructable will show you how to pull a dent from a plastic bumper cover. In this case, the dent was in a 2007 (or thereabouts) Honda Civic, but I'm sure many other cars are similar. I didn't have a camera handy when I did this, but I'll try to explain. The illustration shows the approximate size and location of the dent.

caveats:
-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.

-sponge
-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

Put the pot or bucket over the dent and tape in place. It's easier if you have someone else hold it in place while you tape. It doesn't have to be totally air tight, but there should be no gaps. You may want to take a long piece of tape from the end of the pot up onto the hood or headlight so the pot doesn't fall off.

Step 4: Pull!

Turn the vacuum cleaner on. Put the end of the vacuum cleaner hose over the hole in the end of the pot, more or less as you see in the illustration. You may try rocking the hose a little bit to let some air in. Sometimes a vacuum cleaner will pull harder if it's getting a little bit of extra air.

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.

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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)

Peel off the tape before it leaves residue. You're done. Unless you need to touch up the paint. But that's another Instructable.

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.

-lr10cent
10 cent solutions to million dollar problems. And vice versa.