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Repairing late-model Firebird door panels

Fixing may be easier than finding new ones

Jefferson Bryant - August 19, 2011 09:00 AM

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This is a common problem on 1993 to 2002 Firebirds. This is a high-stress area, so just covering it up is not going to work.

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The door had been repaired previously with fiberglass resin by the owner. Even though they used mat in the resin, it didn’t work because of fiberglass’ limited adhesion to certain plastics, and since it is too stiff, it just pops loose. We removed this repair in one piece with gentle prying.

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The cardboard center piece has to be loosened, but the factory used melt tabs. We had to cut the top off the tab with a razor knife. You can always re-fasten the board (we only cut one) with CA glue or hot glue.

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We used a couple of nylon pry bars to push the center panel away from the plastic panel. Using some 120-grit sandpaper, the edges of the panel were sanded down. It is important that the backside of the panel be sanded down as well. Try to get the edges on the front side. The key to the repair is the beveled edge. Just like welding, the bevel allows more adhesive material in the middle for a better repair.

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To keep the crack from continuing, we drilled the end with a 3/16-inch bit. This takes the stress out of the end of the crack.

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The center panel was taped up so it didn’t get damaged or painted. Then we prepped the repaired area with some PRE prep spray (front and back) from Eastwood. This removes any wax or oil on the plastic for better adhesion.

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The front side of the crack was sealed up with CA glue. Yes, this is a static repair that does not allow flex, but this is just to seal the front side and keep the panel together.

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The backside of the panel was sanded with some 80-grit. You want a nice profile on the plastic for better adhesion. We also wiped it with PRE prep spray.

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This is the repair kit. Everything you need to apply it is included. The kit cost about $7. The adhesive is metered out using the plunger. Both sides of the tube are pressurized at the same time, and the liquids need to be mixed thoroughly. This stuff gels in about five minutes, so be quick.

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You might want to use gloves for this step. First, the adhesive was lightly applied to the plastic, just a base for the mesh. Then the mesh was laid over the repair area. Next, more adhesive was spread over the mesh. After about 15 minutes, the repair is good to go. The adhesive requires an hour to fully cure. It is sandable, but you don’t want this on the front side.

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Once the adhesive had gelled, we sanded the CA glue down with 200-grit. You don’t want big scratches on the front panel. The smoothed CA proved a nice, clean repair.

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We added some light body filler to smooth out any pits or imperfections. In this case, we used some spot putty (the kind that uses hardener), not the stuff in the foil tube. The filler was sanded down with some 200-grit.

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Since the repair removes the factory texture, we have to put it back. This is a trial and error process that takes some learning. First, we laid down a guide coat of SEM Trim Black from about eight inches. The entire panel was sprayed, otherwise the repair will be obvious.

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After the SEM had dried for about 10 minutes, we laid down some Eastwood Rust Encapsulator (matte finish). This coat performs two functions, it softens the gloss and it provides a different level of texture. The SEM is brighter than the Eastwood paint. This creates a differentiating look, emulating more texture than is actually there. It works great. Be sure to hold the can about 10 to 12 inches from the part. This is crucial for the right look.

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Once the paint had fully cured, we reinstalled the door panel. This repair should last quite a while.

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Just as the little Dutch boy learned, repairing cracks often proves more difficult than just sticking your finger over it. Due to the design of our particular model’s factory door panel, there is considerable stress in the upper rear section of the panel.

Within 20,000 miles, just about every Trans Am owner experiences this problem. Since GM stopped producing this panel several years ago, finding a replacement is not easy, so a repair is in order.

There are many tales of how to repair the panels floating around — some work, some don’t. The problem with these repairs is that they do not address the real problem, which is the need to flex. Even a little flex will help alleviate the stress that causes the panel to crack. Most repairs are done using fiberglass resin and cloth, which does not flex well at all. Eventually, it just breaks off. To solve this problem, we had to find a different solution.

The OEMs have been using structural body adhesives for some time now; even the 2000 Trans Am we are working on uses this to secure the doors to the body. This special adhesive is designed to adhere to just about anything — metal, wood, fiberglass, plastic — it does it all. Once cured, the adhesive is very strong yet it has a slight yield; it will give just enough to relieve the pressure while holding fast to the plastic.

There must be a backing for the repair as well; simply spreading the adhesive across the break won’t last unless there is solid structure underneath. This can be steel, plastic or wire mesh. Structural body adhesive must be mixed in a certain ratio, which requires an expensive mixing gun that utilizes metering tubes and mixing tubes. This is great for using the adhesive in large amounts, but all we need is a small batch.

After some research, we discovered the same product in an easy-mix package from Bondo. Yes, this “Bumper Repair Kit” is the same company that brought you pink body filler, but not everything from Bondo shares the same reputation (Bondo is now owned by 3M). The kit comes with a spreader, the adhesive and a strip of repair mesh. You can’t mix it wrong and it has most of what you need for the basic repair. We also needed some CA glue (cyanoacrylate, or super glue), some sandpaper, light body filler, and texture paint.

We spent a couple of hours repairing one door panel on the Trans Am. The finished product looked so much better than the original finish, we will likely be refinishing the entire interior. We drove the car around for several months before writing this story to gauge the longevity. With previous repairs, the cracks showed up within a few weeks, but after several months, this repair has shown no signs of returning.

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