Quarter panels aren't like other external panels that can be easily removed, so look at repairing first and don't rush to replace these robotically welded body parts
Nearly every external panel on a modern vehicle can be removed from its substructure with simple hand tools, by merely unbolting a series of fasteners, except one — the quarter panel.
Unless you're working with some rare exceptions like certain Saturn vehicles, or several other plastic composite vehicles, quarter panels are welded on, and are not simple to replace. Why then, in most accidents where a quarter panel is damaged fairly extensively, is there what appears to be a rush to replace these damaged panels as opposed to repairing them?
There are several things to consider when deciding whether to repair or replace: quality, cost, integrity of the repair and cycle time. Before we get into the nuts and bolts of repairing a quarter panel with damage such as the Buick in Figure 1 we need to look at these considerations and rationalize them.As I mentioned earlier, a quarter panel is typically a welded-on panel. Removing a welded-on panel, in essence a structural part of the vehicle, is often not the most advantageous operation to perform. During installation, robotic welds are usually more precise, and when done in the controlled environment of a manufacturing facility, are better than the welds performed by humans in the field — unfortunately.
Basically, with regard to safety and integrity, my motto is: If you don't have to cut a car apart to repair it — don't cut it.
When looking at a damaged quarter panel, always think: repair first; replace second. Again, addressing cycle time, you can usually begin repairing a panel immediately after receiving authorization. If you replace the panel, obviously, you are not able to fully proceed until you receive the parts. This problem can become exacerbated when backorders and delays occur. More often than not, a panel can be fully repaired and be ready for paint in the time it would take for the parts to arrive. Additionally, one of the most beneficial aspects of repair versus replace is that generally, your shop will make a better gross profit on labor than it will on parts.
Repair vs. replace?
If quality and safety are better, cycle time is lower and profit is higher, so why wouldn't your first option in most cases be to repair? Obviously, there will be cases where a repair is not feasible, for example, when the panel is nearly torn from the vehicle on impact, or is severely damaged. These examples must be looked at on a case-by-case basis, as all repairs are. It's a good idea to be open-minded, and make some preliminary pulls to a damaged panel, before making your final decision regarding reparability.
It's true that when you make your initial diagnosis of repair and map out your plan by writing a comprehensive estimate, you may have time constraints involved. Usually, with a DRP, you have to write an estimate in a certain time frame. However, if you contact the responsible party, whether it be the vehicle owner or your DRP partner, and explain that in an effort to write an accurate blueprint for repair, you want to perform some pre-pulls prior to finalizing your estimate, more often than not, you'll be allotted extra time to try and get it right. Good communication is the key to keep repairs moving smoothly.
Diagnose the impact
When straightening sheet metal damage, it is important to study the impact to try and determine how the impact occurred. By this I mean the direction of the damage in sequence, not what object caused the impact. To repair a panel effectively, you must pull out the damage in the reverse of how it occurred. Doing so will eliminate undue stresses on the panel, and it will pull out very easily. Let's look at our Buick and try and determine how the damage occurred, and consequently how we should repair it.
The right rear quarter panel on this Buick (Figure 2) is fairly severely damaged and it could be equally argued for either replacement or repair. The outer surface of the panel is bowed in the center, and the rear section has multiple types of damage. The impact to the vehicle was at the right rear corner of the vehicle, nearly straight on, with a slight angle inward, toward the trunk area (Figure 3). The lower section of the panel has the most severe damage, but considering it's hidden behind the bumper cover, and the surface is already molded in an uneven pattern, repairing the lower should be okay.
If we just opened the trunk and started to beat out the damaged panel, we would distort it, stretching the steel and making it virtually unrepeatable. What we need to do is place a hook and chain at the origin of impact, which we have already determined as stated earlier, and using a floor post and pots, gently begin to pull the damage rearward and slightly right. This vehicle did not sustain unibody rail damage, so pulling it on the floor is acceptable. (You can pull it on a bench if your shop doesn't have floor pots.) This is a simple pulling setup that you can charge a small amount of labor for on your estimate. You may have to reposition the chains and post to pull from different angles as the damage is removed (Figure 4). This also keeps the metal from distorting.Don't apply heavy pressure, as you are only pulling sheet metal, and too much pressure too fast will distort or tear the sheet metal. As you apply pressure, begin to work the damage out from the inside of the panel. Since you properly determined the sequence of the damage, the panel should pull out with little effort.
You can see that the large impression in the center of the panel was caused by pressure, and that by relieving that pressure by pulling the damage in reverse, the dent virtually disappears. Continue to pull and rough out the panel until it is back to its original shape (Figure 5).If you can't access the inside of the panel, you can use a stud gun and puller to work the damage out from the outside of the panel while pulling. Use the taillight and the bumper cover to determine proper fit while straightening (Figures 6 and 7).
Now we have the finished pulled panel, and are ready to begin metal finishing. Note how well the damage pulled, and how close to original conforms the panel is, even before filling operations have begun (Figure 8).
Sanding the right way
Years ago, I would have taken my big, two-fisted grinder with a 36-grit disk on it and attacked any given quarter panel, sparks flying everywhere, in order to get the panel cleaned and ready to apply plastic filler.
On today's vehicles, a grinder like that would blow right through the sheet metal in a few seconds. Making vehicles more fuel efficient requires lighter sheet metal, and lighter sheet metal requires less aggressive tools.
The first thing you should do before beginning to sand any panel is to solvent wash it using a good grade wax and grease remover. This operation is extremely important and will prevent waxes and oils that are on the surface of the paint from being ground into the sheet metal — and it will help avoid issues with adhesion of the new finish later.
Using a dual-action sander, remove the paint in the damaged area with a 40-grit disk. This will remove paint effectively, without overheating, distorting or damaging the sheet metal.
Once all the paint and primer is removed, the panel should look like our panel in Figure 9. Since we spent the proper amount of time diagnosing and pulling the damage, only a small amount of filler should be needed to finish out the panel.Be sure to dress any damage that was caused during the pulling and straightening operations, especially areas that should be sealed, such as the joint area in the rear of the panel.
This area had to be re-welded using a MIG welder, and then a coat of seam sealer was applied. Before the panels were re-welded, though, a weld-through primer was applied to the surface. Weld-through primers are available from your paint jobber and are essential parts of a long-lasting weld repair.
The inside of the repair panel also sustained damage, obviously, from the pounding and probing that was done during the repair operation. This action may have removed any factory protective coating that was on the inside of the panel, and in order to restore the integrity of the panel, the protective coating must be re-applied.
There are several spray-on products available for this operation, depending on what the factory originally used. I prefer an epoxy coating for this step, since it is very durable. Prep the inside of the panel, according to manufacturer's directions. As I have said many times before, always follow the manufacturer's directions as close to the letter as possible. Doing so will avoid possible failures throughout the life of the repair.
Mixing the mud
Correctly mixing plastic filler, or "mud" as most techs affectionately call it, is a skill. In fact, it shouldn't be mixed at all; rather the hardener and the resin base should be folded into each other smoothly to prevent air from being pushed into the mixture. Air causes pinholes in the plastic filler.
I would suggest reading and following the filler manufacturer's directions closely to achieve the optimum performance from the product. This sounds elementary and basic, and it is — but it is often rushed and done improperly, resulting in many issues later, especially for your painters.
Once your filler is mixed, apply a thin, even coat over the entire repair area. Work to smooth the filler fairly well, but don't be concerned if it isn't perfectly smooth on your first coat. This isn't like house paint; you absolutely do not want "one coat coverage." An initial film build that's too thick will stand a greater chance of failing later.
Once the first coat is dry, sand it to conform using a "mud hog" or a long board air file. Blow off the panel between each successive coat of plastic that has been sanded to remove any residue.
Once the panel is smooth and flat, apply a final coat of polyester putty to be used as a final glaze to remove any minor imperfections.
Prep and finish this last coat per the paint manufacturer's directions (Figure 10). Once this is completed, prime the repaired panel, prep and paint it using the system of your choice.The bottom line
I started this article talking about repair versus replace and the associated gross profit resulting from both methods of restoration. In this example of the damaged Buick, I have calculated the gross profit (GP) of repairing the vehicle, repairing the panel as described above, and of replacing it.
In this instance, the repair order's total dollar amount ended up being higher with the replacement operation, but the GP was higher with the repairing operation. I believe all shops are in business to make a profit, and a higher GP is usually more important to most shop owners and managers.
This vehicle was repaired from drop-off to delivery in two working days. That's a cycle-time mark that would be difficult to hit if the panel had been replaced.
This is a win-win situation for all parties involved. The shop makes a higher level of profit, satisfies the customer and controls cost all at the same time. To me it's a no-brainer. Happy hammerin!
