Door Panels Done Right

Jan. 1, 2020
Over the years the replacement of the outer door panel or complete door shell versus repair of the panel has certainly increased. Has this occurred due to the available technician skill in the current workforce, the costs of repairs quickly exceeding

Today when analyzing damage to determine whether a complete door shell is needed, an outer panel can be replaced, or the damages can be repaired, there are several factors to consider. First and foremost should always be, "What are the customers' expectations?"

Over the years the replacement of the outer door panel or complete door shell versus repair of the panel has certainly increased. Has this occurred due to the available technician skill in the current workforce, the costs of repairs quickly exceeding the costs of replacement (on the surface), or other factors that may include the reparability of today's steels and manufacturer's requirements? For sure what was once a "dreaded task" 20 years ago is one of the most common operations today.

Replace vs. Repair

Today when analyzing damage to determine whether a complete door shell is needed, an outer panel can be replaced or the damages can be repaired, there are several factors to consider. First and foremost should always be, "What are the customers' expectations?" Yes, a customer may have a very narrow understanding of what and how we restore vehicles back to pre-accident condition, but we must ensure that at the onset of the repairs, we are aware of their expectations. We must communicate to them what we are doing.

After this, are the damages non-repairable due to something beyond the damage visible on the outer panel? Is there damage to the inner door I-beam? Unfortunately, at the estimating stage one is not able to see much of the door beam to determine if it is damaged. Knowing the location of the door beam is important, but it will vary in design and location on many vehicles.

In most cases if there is damage to the inner door beam, the complete door shell must be replaced. Otherwise the determination is often whether the extent of damages and the repair associated with each option (repair vs. outer panel replacement) are more economical.

Unfortunately, it also can be based on the facility's technician base and their abilities and equipment available. There are several new tools on the market that provide for more repairs versus replacement, but for the most part shops are limited to equipment that has been available for over 20 years, such as basic stud or pin welders, and quick pull clamps. The scope of this article is not on repair technology equipment, but NACE is coming in a few months and there are several fairly new options to consider.

I hope someday the rules for economics of repair also factor in other costs that may increase or decrease the overall cost of the job. There are costs associated with repair that are not a factor, or they are much less of a factor, when panel replacement is selected. These costs include additional materials used in the repairs and preparation of the panels. These items are often not considered additional costs. In addition, today's estimating systems will warn estimators when they are reaching repair thresholds, however, they do not consider the overall savings that may occur when repairing a specific panel.

ESTIMATOR TIP: If the extent of damage to the outer panel has eliminated the possibility of repairing it, cut windows in the outer panel to be able to evaluate whether the inner door beam has been damaged. If not, possibly an outer door panel replacement would be the choice for repair and not a complete door shell.

TECH TIP: If cutting an access opening for outer door handle removal or access to the inner door beam for inspection, make sure not to cut into the inner door beam.

Outer Panel Replacement

There are three basic replacement methods that are possible once the decision has been made to replace the outer panel:

  • Mechanically fastened outer panels
  • Adhesively bonded plastic outer panels
  • Conventional Hemming flange replacement

Mechanically Fastened

There are vehicles, such as the Saturn, that utilize mechanically mounted door outer panels and various other panels. Often, the entire refinishing operation is performed prior to installation for this mechanically mounted panel. The adjacent panels are either being replaced if necessary or as blend panels are mounted on stands rather than the vehicle masked conventionally. Then the panels are reinstalled by the technician.

ESTIMATOR TIP: Pay close attention to any damages to the inner door and ensure corrosion protection is properly restored. Also, since the panel is attached with special fasteners, there are often replacements required from removal.

TECH TIP: Pay close attention to the inner frame and make sure it properly aligns with adjacent panels. Make sure fasteners that will need to be replaced are identified and the estimator is informed. Often there is an installation sequence, tightening order and torque specification for these special fasteners. If not done properly, the plastic panels can crack during installation and fail to expand and contract properly during temperature changes.

Adhesively Bonded Plastic Panels

There are vehicles with complete Sheet Molded Compound (SMC) door shells with outer panel replacement panels available. The replacement method requires the removal of the outer panel by breaking the adhesive bond between the inner door panel and outer door panel.

The bond should be broken by a combination of heat and careful use of an air chisel with a fairly flat, dull bit approximately 1 to 1.5 inches wide. It's also very important to understand that the heat range used to completely break the adhesive bond (400-500 degrees F) may damage the SMC as well. Heat should be directed from the side of the outer panel, and only to begin the softening of the adhesive. Then carefully use the flat bit to break the adhesive bond. It's important to carefully direct this wedge into the joint to avoid damage to the inner door structure. Remaining adhesive will require grinding/sanding off to allow for the proper thickness during new application.

ESTIMATOR TIP: It is important on either of these two types of outer panels that careful examination of the inner structure is performed since the plastic outer panels will disguise the damages internally. Often the plastic outer panel will return to almost an undamaged state or relatively minor damage will be visible when the inner structure is beyond repair. For complete SMC door shells, there are often steel inner structures riveted to the SMC inner panels. Look for cracked or pulled rivets and bolts on the inner structure indicating extensive inner damages.
TECH TIP: Removal of the outer SMC door panel can be tedious since the heat and air chisel can damage the inner panel. It is advised to rough cut the outer panel out within a few inches from the outer bonded perimeter and cut the remaining areas into strips. This will allow you better access to the adhesive joint. Also you may need to grind off the outer edge of the outer panel to expose the adhesive joint.

Hemming Flange Replacement

The vast majority of outer door panel replacements will fall under this category. This procedure has been basically the same for a few decades, however, I have recently visited shops that still allow technicians to "beat" the flange onto the door inner panel to the point where it requires the application of body filler around the entire outer panel perimeter; even to the point the repair would have had less. This practice is simply unacceptable, but many technicians are not aware of tools and techniques to prevent this.

Removal and Inspection

Generally the method used for decades has been to grind the outer edge of the panel until it exposes the three layers: outer panel, inner panel and the flange. There are tools available that will allow you to bend the hemming flange back to 90 degrees after the spot welds are removed. This would be just in case you want to save the panel and reuse it. Of course in our industry, this may not ever happen, but in restorations and many other countries this may need to be done.

Once the outer panel is removed, the inner panel flange should be inspected and any corrosion removed. Often, minor straightening is required to the inner frame at this time.

ESTIMATOR TIP: The time to straighten the inner frame is not included in the replacement time, and there are additional operations required for removal. Based on the estimating system being used, the removal and reinstallation of the belt molding, glass, mirrors and other trim items may not be included in the outer panel replacement time. Any electric power accessories and wiring will need to be added based on the vehicle options. Keep in mind, too, that decoding the VIN number will not identify all vehicle options in regards to the estimating systems. Windows should always be removed if the method of replacement will include welding. This may require the replacement of special fasteners and/or rivets.

TECH TIP: Before removing the outer door panel make sure all power accessories are working. Troubleshooting a problem that may or may not be accident-related on the day of delivery is no fun. Check these out before removal if possible. Include mirrors, locks, windows, etc. Make sure to test the window operation if possible, you may find the intrusion beam or track is damaged and the window will not roll down correctly.

Finally, make sure the door aligns to the opening and opens and closes properly. This may include cutting some of the outer panel off to allow the frame to be straightened and used for adjacent panel alignment. This is especially needed when the adjacent panel is being repaired or replaced. Don't take the door off until you are sure it will align properly and if it is needed for the adjacent panel.

Installation

There are three basic methods for installation: re-flanged and welded, re-flanged and adhesively bonded, or a combination of both. The choice is normally based on both manufacturer recommendations and design of outer panel attachment, and shop preferences. Today, many of the door outer panels are attached using a combination of welding and adhesive bonding. If they are, for all practical purposes, they should be replaced in this manner. Even if they are adhesively bonded from the manufacturer, one should consider adhesive bonding to improve the corrosion protection it offers. There are few if any to date that do not recognize and approve adhesive bonding for outer door panel replacement.

The installation follows after the inner door frame has been straightened and verified correct. This may take several trial fits of the new outer panel and to the vehicle depending on how extensive the door was damaged. In this process the flange is prepared and the proper primer is used for the inner panel flange. There are several options for this based on both automobile manufacturer and product recommendations by the adhesive manufacturer.

Also there are anti-flutter adhesives used to bond the intrusion beam to the outer panel and sound deadening pads to consider. These must be restored according to vehicle manufacturer recommendations using the proper products.

ESTIMATOR TIP: Even though basic alignment and trial fit may be included in the replacement time of the outer panel, multiple trial fits are not. Also the corrosion protection, door bonding adhesives, sound deadening materials and anti-flutter materials are not included in paint and material calculations or in labor calculations.

TECH TIP: It is important to check and protect any items left attached to the door. The replacement of the anti-flutter materials attaching the door I-beam to the outer panel is a material specially designed to not expand and damage the outer panel when curing. Often you should not use the same materials used for the flange bonding unless specifically stated otherwise.

Tools

The improvement of special hand tools has evolved nicely for the last number of years, but to begin with start with the basics. Use the correct hammer and dolly for the operation. There are specially designed hammers to fold the flange over without excessive damage to the outside of the panel. Then use smooth wooden blocks and "shot bag dollies" on the outer panel side of the panel.
One of the first tools designed to improve the flanging process was an attachment designed for the air chisel. I had one way back in the day until it did its "normal thing" for the third time and I threw it through a window in the shop. Unfortunately when I talk with technicians about door skinning tools, many are still thinking of this early entry. As I stated before, NACE is right around the corner and I am positive the tools that will improve this operation will be there.

MANAGEMENT TIP: There are several fairly new tools available to make this replacement operation much more efficient than in years past. Invest in these tools and provide employees with the training and practice to use them properly.

TECH TIP: One of the most important tips I can give before the actual "hammering" begins is to chamfer the corner of the outer door panel with 80 grit on a grinder or D/A before beginning to fold the flange over. This will allow the flange to fold easier and not decrease the thickness of the metal to the point of weakness. (Figure 1.)

Completing the Replacement

Once the flanging is finished there may be several areas to complete the installation. A couple to mention in this article include: welding areas and special seam sealers. However, restoration of additional corrosion protection, re-installation of internal parts, re-installation of the door, refinishing steps, exterior trim replacement and/or re-installation, and verification of the door and its components operation are all important. I simply have run out of space to discuss it.

Welded Areas

The welds may be required due to the design of the panel and if sectioning is performed. This also may require the use of weld-thru primer based on the manufacturer's recommendation whether to use the product or even possibly an alternative product. These welds can be replaced with Gas Metal Arc Welding (GMAW) Plug Welds or may be replaced with Squeeze Type Resistance Welding (STRW). This must be determined by first the automobile manufacturer methods approved, and then by what equipment and training you have available.
TECHNICIAN TIP: Make sure to finish the weld completely around the plug weld hole when using the GMAW process. The strength of the welds will be compromised, otherwise, and the pinholes, cracks and gaps have to be identified as the main failure locations in corrosion protection tests. Also consider the STRW to make the replacement match the "OEM Look."

Seam Sealers

Today there are several vehicles that have a very special look to the inside flange joint. This is usually a result of a special bead of seam sealer. These designs are difficult to match but there are several aftermarket suppliers that have products designed to accomplish this.

This step of the operation is often overlooked and not considered important, but it is! Just as our industry 25 years ago didn't think much about overspray inside the door jambs as important, today the final appearance of the outer door panel replacement should also not obviously indicate it has been replaced.

ESTIMATOR TIP: The process of recreating the inner seam sealer appearance is not included in the outer door panel replacement. It also is just not a basic "seam sealer" operation and its product costs is not part of the paint and materials calculations.

Labels on the inner door must be replaced if needed. The water barrier plastic if damaged during removal must be replaced along with many vehicles may now have a side impact foam panel attached under the inner trim panel. These are to be replaced even if it is just removed for access.

TECH TIP: There are special products and rollers available to recreate the appearance of the seam sealer. They may include special sealer products, such as a tape from many aftermarket suppliers. The proper use of these products is required or adhesion will be lost. Putting sealers over self-etching primers have caused problems as well due to the evaporation of the acid within the primer that is blocked by the seam sealers and the acid causes the seam sealer to lose adhesion.

Using some ingenuity may allow standard seam sealer to be used to duplicate the appearance of some designs by using a stout piece of paper, such as a business card, and creating a template by cutting a slot the width and height of the needed design. Place the seam sealer on the panel in an even small bead slightly larger than what is needed and drag the template along the seam. You will need to create multiple template cards in most cases.

Final Thoughts

After the outer door panel is replaced the panel should not have a need for body filler except where sectioning has been performed. This is a goal you should have for each time you replace an outer door panel. When the door is opened as well it should not be obvious the outer panel has been replaced.

Of course transport damage on the new panel may also need to be repaired. However, if the tools and techniques provided in this article are followed, I am sure you will have a better-finished product in a more timely manner.

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