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This project is not for your everyday door dinger from bumping another car or object in the street --these dents require repairs that involve more than a hammer and body-filler. We're talking about a dent --one that is big enough to stretch the metal well beyond its original shape. For this sort of door damage, you have two options --find another door at a wrecking yard, or reskin the door you already have. Recent developments in structural adhesives make the second choice a good alternative, with no welding required.
Most sheetmetal doors are made in three pieces. There's the frame (which the inner door panel and armrest attach to), the window channel (which is welded to the doorframe) and the skin (which attaches to the doorframe and the outside of the window channel).
Step 1: Taking Off the Door
To replace a skin, you must first remove the door of the car. Procedures vary depending on the vehicle, but the place to start is by taking out the inner door panel and the window glass. Next, remove the insert inside the window channel, and any trim or molding around the window frame and on the door skin. You also have to remove the mirror, and the door lock and handle. Use a body shop repair manual specific to your vehicle if you have doubts about how to remove these items without doing damage. Unplug any wiring that runs from the body through to the doorframe. Next, scribe around the door hinges on the car body to mark their location, then have an assistant hold the door while you unscrew the hinge bolts. Keep in mind that even with much of the inner workings of the door removed, it is still heavy, so get some able-bodied help.
Step 2: Removing the Skin
With the door off the car, you can now begin to detach the sheetmetal skin. The perimeter of the skin is folded over the doorframe at the factory. Grind on the edge of the door's perimeter until you separate the folded flap on the back side of the door from the skin that forms the door surface. Be sure not to grind away too much --when you see the gap, move on. Once you've gone around the entire door, you should be able to peel away the folded sheetmetal from the doorframe. Wear eye protection and gloves when grinding --the metal's edges are sharp.
Step 3: Banishing Welds
With the folded portions of the skin removed, look for spot welds that hold the skin to the frame. They're likely to be found across the top of the door skin near the base of the window opening, the area surrounding the door mirror attachment points and also under the door handle. Spot welds are often difficult to see; it's most effective to look for their telltale indentations by using a strong light held at an angle. When you find a weld, mark the spot with a felt pen. It's possible to remove the spot welds by simply drilling through them. But this leaves holes in the doorframe. Instead, use a special drill bit made just for this task. It's sold at auto parts stores that carry body shop supplies. Because the bit's teeth surround the spot weld, the bit cuts the metal of the skin around the weld but leaves the frame undamaged.
Step 4: Getting Out the Kinks
Split the last vestiges of spot welds and seam sealer apart. You'll have to persuade them with a chisel in order to set the skin loose. Once this is done you should be ready to separate the skin from the door frame.
Step 5: Pry and Prep
With the spot welds removed and the folded portions of the skin ground away from the frame, gently pry the skin from the door. If you meet resistance, stop and make sure all the spot welds have been drilled out. Manufacturers also put sealer between the door skin and the side-impact beam. (This is a solid metal piece that runs behind the skin and connects to the doorframe.) You'll have to pry this joint apart. A crow bar works quite nicely.
When you have it apart, you'll want to clean it. Trust us, the inside of the door is dirty. You could use compressed air --but you may even have to pressure wash it. Use your body grinder to take off the small circles of spot-weld material left on the frame. Also grind off or sand away any putty, glue or other materials that will interfere with installing the skin. Then give the doorframe another cleaning.
Step 6: The Replacement Skin
There are several ways to buy a door skin. If your car or truck is less than 10 years old, you can most likely purchase one at the dealer. Replacements are also available from aftermarket suppliers, and are sold online and at many auto parts stores. Keep in mind that factory door skins usually are more expensive. For instance, a 1998 Chevy pickup door skin costs about $350 from the dealer. An aftermarket skin costs about $260 with shipping. No matter where you get your skin, open the box and check it immediately. These things get damaged even more easily off the car than on it. Before you start applying adhesive, place the doorframe on a table with the skin side facing up. The portions of the sheetmetal that fold around the doorframe are pre-bent at 90-degree angles to the skin. That way the skin will properly self-locate around the frame. Before installation, place the skin on the frame to test its fit, then remove it. You'll probably have to grind away a few imperfections or tap out high spots for a perfect fit. This is an important step --any misfit will be impossible to correct once the adhesive is in place.
Step 7: Adhesive Application
The adhesive and its applicator are available at auto parts stores that sell body shop supplies. The door adhesive that we used (Non-Sag Door Skin Adhesive) comes in two 7-ounce containers and needs to be mixed in equal parts. We bought a dedicated applicator, made by the adhesive maker, for about $65 --about the price of both containers of the adhesive. The applicator gun and its disposable nozzle mixed the components as we applied them. This particular stuff takes an hour to set up.
Don't think you can do this job with some 5-minute epoxy. Use a product that is intended for auto body repairs. The adhesive is temperature-sensitive. You need to work in an area where the temperature is between 60 and 85 F. If it's too cold, the adhesive won't set properly; too much heat hardens it before you can get all the clamps set properly. To attach the door skin, apply a 1/4-in. bead of adhesive from the applicator onto every surface of the frame that will come in contact with the skin. Apply several large dollops of adhesive to the side-impact beam so the middle of the skin will fasten to it firmly.
Step 8: Add Security
Use spring clamps or small C-clamps --a lot of them--to hold the skin in place as the adhesive cures. Be sure that all parts of the skin make contact with the frame. Wipe off excess adhesive with a paper towel. Let the adhesive harden for 2 to 3 hours. Then, after removing the clamps, place a piece of old but clean carpet on your worktable and set the door on it with the skin facing down. Check again for excess glue, and either sand or grind it off. Then, using a bodyworking hammer, start at one corner of the skin and work all the way around the perimeter of the door, bending the tabs down along their length until they are flat against the frame. Take this last step slowly. Go along every seam several times to completely crimp the metal over. Don't dent the outside of your new door skin.
Step 9: Finishing Up
Now the door is ready for primer and paint. Don't forget to paint the inside of the skin first to prevent corrosion. Follow the paint manufacturer's recommendations as to how many coats are needed and drying times. Keep any drainholes along the door's bottom edge clear of adhesive and paint; if they are blocked, water will collect inside. Then you and your helper can reinstall the door on the car, making sure to align the hinges with the marks you made on the body. You may have to make slight adjustments to get the door gaps right, since the new skin might fit slightly differently. Once the door is back on the car, reinstall all the pieces you removed. Crimp the flange by using a body hammer to carefully tap the excess metal over and up tight against the frame.