(...that doesn’t get under your skin)

Door skins can be difficult to replace, but going step-by-step ensures a proper repair

By Charles Wilhite
Contributing Editor

Replacing door skins are one of those jobs that few technicians look forward to doing because efficient, problem-free door skin replacement is an exacting process that takes practice to master. Some designs have bolt-on outer panels like most Saturn models, while others have composite outer panels that are bonded in place. Then there are those door shells that are only serviced as complete parts. The Audi A8 uses a modular design where the outer skin is serviced with the lower part of the door shell. This unit is bolted to the upper shell and intrusion beam. But the most common assembly is the rolled edge attachment along the flange of the door shell. This seam is difficult to reproduce with hand tools, and often the results require extensive repair with plastic filler to straighten the damage to the edge of the new panel.

Disassembly
The first step in replacing a door skin is to remove the door from the vehicle. In some situations, particularly if the fender has been removed, it is possible to replace the skin while the door remains on the vehicle. Even so, it is best to work on the door when it is off of the car. Electric wiring harnesses are usually modular with a plug at the front of the door shell or just inside the hinge pillar. On some vehicles it may be necessary to completely remove the wiring harness. Label or make a sketch of the position of the wiring harness if any of it must be removed from the shell. While it may not seem to matter all that much, if the wires are not put precisely back where they were they may get caught in the window mechanism when the vehicle is reassembled. Welding and grinding will produce hot metal that melts into glass and plastic, so removing the window glass and any trim or speaker components is also a good idea. Covering them with protective paper may be an option. 

Getting the door off the hinges is usually accomplished by removing the hinges off either the door shell or the hinge pillar. Examine the mounting system to determine which will be easier to realign when the doors go back on. Some hinges are adjustable at one location only. If it is possible to leave the adjustment in place, the door should fit after the skin is replaced. Some vehicles require the hinge pins to be removed, which may require special tools to drive them out and back in.

Grinding the Edge
Once the door is off of the vehicle, support it on a work stand so it cannot move very much. Arrange the stand so the new skin will not be dented when it is installed. To remove the skin, the folded flange seam must be ground off or opened, and any welds must be ground off. The most common practice is to use a grinder and grind off the metal at the edge of the door skin. This allows for removal of the skin. The bonded and welded ribbon that is left can be peeled from the door shell. The noise of grinding the edge of the door is one of the most irritating sounds produced in the collision shop. The door shell acts as a resonator for the sound. It is also loud enough to require hearing protection. Of course, eye protection is also necessary because of the flying sparks. When possible, the sparks should be directed to the floor so they cannot travel far and cause damage to other vehicles nearby. 

An alternative is to peel the flange away from the door shell with a pair of end cutters. Unlike most wire cutters, which have the blades on the side of the tool, end cutters have the blades on the end, hence the name. This tool may be worked along the edge peeling the skin open like a can after any spot welds have been ground away.

When you have the edge flange loosened from the shell, the skin is almost ready to come off of the shell. If the skin goes all around the window opening, that part of the skin may be left of the shell. The skin will be sectioned into that portion, typically just above the belt molding line. Other designs have a seam weld at the top of the door skin that must be ground away. The last piece of the puzzle is to loosen the adhesive usually found between the inside of the door skin and the door intrusion beam. This is a flexible foam placed there to dampen sound. It should be replaced when the new skin is installed. One effective method is to use heat on the outside of the damaged door skin to soften the bond. This will allow the door skin to be cleanly pulled away, leaving the foam intact. You can apply a small amount of adhesive when installing the new skin to reattach the foam. 

Repairing the Shell
Door damage is not limited to the door skin. The door shell and the door intrusion beam must be carefully inspected before making the decision to replace only the outer panel. The door intrusion beam is a critical safety component and must be replaced if it is damaged. Very few intrusion beams are serviced separately; on most vehicles the whole door will need to be replaced if the beam is bent. The door shell can be repaired quite easily if it is slightly damaged at the edge once the door skin is removed. Damage that is more extensive will need to be evaluated for cost effectiveness of repairs. 
Grind any welds flush with the surface and remove excess adhesive and seam sealer. Bare metal that will not be covered with adhesive should be primed before installing the skin.

Replacing the Skin
Door skins were first bonded in place in the mid-1970s. Today, door skin adhesive is common in production and should be used when replacing door skins. Most manufacturers recommend that any welds also be replaced. Preparing the surface should be done following the adhesive manufacturer’s instructions, but generally requires cleaning and only light scuffing of any primed surface. Bare metal may need to be primed. 

The adhesive may be put on the door shell or the skin. When placed on the skin, it is more likely to be squeezed around so it covers all four surfaces formed by the skin folding around the shell flange. This provides the strongest, quietest and most corrosion-resistant repair. If the amount is just right, it may also be used as the seam sealer.

Folding that Edge
The hardest part of skinning a door is folding over the edge. There have been various tools developed to accomplish this task the way the factory does, but most are difficult to master. The old-fashioned hammer and dolly method is still the most commonly used. Because the door skin is bonded in place, the flange does not need to be smashed completely flat and the adhesive will provide a cushion for the hammer blows. Examine other doors on the vehicle to judge how flat the flange should be, then try to make the repaired door look the same.

Position the door skin in place and hold it with a few clamps so it does not shift during the folding operation. Start at one side, holding the dolly firmly and absolutely flat against the surface of the skin, and gently tap the edge from 90 degrees to 60 degrees. 

Generally, it is best to work all around the edge two or three times, folding the lip evenly in steps until it is flat. Which variety of hammer and dolly you choose to use is a matter of style, but some guidelines apply. The goal is to fold the lip without leaving any dents, so the larger the surface area the better. Some sections may be best struck with a flat hammer head, while a gently rounded head may work better in others. On the skin, you should use the largest dolly that will fit the contour. This may mean using more than one dolly on some doors. Some vendors sell special door skin dollies with padded covers. Some technicians put duct tape as a pad on a toe dolly. Others use leather bags filled with shot. 

One alternative to the hand hammer is an air hammer. With the air pressure turned down low, a rounded head in an air chisel can be quite effective, if a little noisy.

Fitting the Door
It is best to test-fit the door at this point to make sure it fits the opening. Small adjustments can be made while the adhesive is setting and before the welds are made. Some technicians will weld the belt line seam while the door is on the car and let the adhesive set before continuing. If there are spot welds they may need to be replaced. This can be done by cleaning out adhesive from the area and using a plug weld.

Finishing Up
When the adhesive is set, the door is ready for refinishing. Seam sealer may need to be applied to the flange area before color is applied. After the door is painted, corrosion- resistant material should be sprayed inside the shell. All mechanical and electrical components should be replaced, checked for operation and adjusted as needed. 
With care this task can be accomplished efficiently and produce a nearly invisible repair.