You need to consider a lot of factors before performing even minor roof work
A couple of weeks ago, I found myself in the office of one of a group of 18 collision shops, training the office management and staff on the finer points of management system use. During that training session, there happened to be a representative of an insurance company conducting a drive-in at the facility.
I make it a point that while I am at any shop, I always try to be attentive and eavesdrop on the conversations going on around me. I think it gives me a truer perspective of what happens during the "real" day-to-day operations of the shop.
This instance was no different.
In this particular case, the facility manager and the insurance company representative were discussing the finer points of a proposed paintless dent repair project on the roof of a Toyota Prius. After some debate, an agreement was reached on the PDR process and cost, and the discussion moved to other areas of damage.Later that evening, while researching some repair data on one of my favorite technical resources, I remembered the conversation that took place earlier that day and decided to look up the manufacturer's recommendations regarding roof repairs to the Prius. I was very surprised when I pulled up Toyota's recommendations for PDR repairs. Basically, per this particular technical service bulletin (TSB), Toyota did not recommend PDR repairs of any kind, on any panel, and if, in fact, repairs were undertaken utilizing PDR, the vehicle's warranty would be voided. I couldn't believe it. I quickly realized that the bulletin was dated 1994, and repair methods had evolved since then. Today, Toyota does recognize PDR repairs as viable, but only with certain stipulations attached. I printed the TSB and brought it with me to the shop the next day.
That event was a timely one since I was already in the process of writing this article, and it provided me a few more angles to pursue in beginning to discuss roof repairs and replacement.Construction basics
There are several different types of roofs used in the construction of the modern automobile. These include roofs with T-tops, removable hard tops, sunroofs, retractable hard tops, convertibles, panoramic glass roofs and solid metal stationary hardtops. Each one is unique in function and repair methodology.As with all safety related repairs, you should never deviate from the manufacturer's recommended procedure regarding replacement. Always consult OE specs when doing this type of repair. Let's look at one of the most common roof configurations that you will see most often in the daily operation of your facility.
Many vehicles today have a power glass panel sunroof or moon roof installed in them. Not that many years ago, these were fairly rare to see in factory-built vehicles due to the expense involved in building them. Over the years, many aftermarket applications were developed to help the average vehicle owner have this luxury item installed for a reasonable price.Today however, even entry-level vehicles include sunroofs as standard equipment. The glass panel complicates a roof repair or replacement because of the many components attached to the sunroof to make it function. Things like tracks or guides, electric motors, drain tubes, limit switches and wiring can make it a challenge to replace or repair a roof panel with this equipment. You also have to keep these components in mind when considering repair viability since they might have also sustained some damage in the incident too.
To fix or not to fix....
Roof panels on most vehicles are strong. Some are integral parts of the unibody and are difficult to repair conventionally. This is mainly due to the fact that the outer skin is fairly thin standard sheet metal that "oil cans" during the repairing and filling process (generally the roofs structural strength comes from the bows under the skin). It is very difficult to repair sheet metal that has this much flexibility in it.
When looking at a damaged roof and attempting to determine the viability of a repair vs. replace scenario, you must carefully examine this issue. It is our obligation to return the vehicle in question to pre-loss condition. Will it be possible to perform that service with a repaired panel? Will the labor cost to repair a panel be higher than the cost of replacement? If the damage to the roof's skin is repairable, is there damage to the internal structure? Are the guide tracks for the sunroof damaged? Is there damage in the areas of the windshield or back glass aperture? If so, will the glass fit and seal properly after the repairs have been completed?
Consider all the options before making a decision. All of these questions must be answered when determining reparability. Additionally, inspect the panel for previous repairs. If the panel has been fixed previously, you will need to remove it entirely before undertaking your repairs. This is necessary since you have no idea regarding the quality or integrity of the prior repairs and cannot risk performing another repair over the top of an improperly performed one.
PDR problems
As in the story I reported at the beginning of this article, shops need to determine if small hits like hail damage can be repaired on a roof panel utilizing PDR. That answer normally depends on the number of dents in the panel, the severity of the damage and the location of the damage. In general, when the dents on a panel pass 300 to 350 in number, it may be a candidate for either conventional repairs or roof replacement.
Even if there are fewer dents, if they are located in difficult-to-access areas, they may not be repairable with PDR. Remember the Toyota TSB? Some manufacturers will not warranty PDR roof repairs if the corrosion protection on the underside of the repaired panel is not replaced, if holes are drilled for access or if the paint surface on the repaired panel is damaged in any way. In the TSBs I have read, the manufacturers have described microscopic cracks in the paint that can occur during the PDR process. They are so small, they cannot be seen with the naked eye. The existence of these tiny cracks may void the vehicle manufacturer's warranty. Make sure when considering PDR, or conventional repairs, you fully understand the vehicle manufacturer's stance on these types of repairs.
Don't misunderstand me. I'm not against PDR in any way and firmly believe in the "repair first" philosophy. However, it's important to consider all potential scenarios before touching a tool to a panel. I suggest you always refer to a reference source such as ALLDATA, I-CAR or vehicle-specific manufacturer guidelines before making a final decision.
Panel replacement
One part of the replacement operation on a roof panel that I really like is the fact that it is generally acceptable to use a structural adhesive to bond the panel to the substructure, making a roof replacement a much cleaner and faster job than a traditional weld-on panel. Let's look at the steps involved in a typical roof replacement scenario on a vehicle with a glass moon roof/sunroof panel.
1. Inspect all adjacent panels for proper alignment. If necessary, measure the door aperture and roof position to assure proper position.
2. Cover the interior of the vehicle with welding blankets and plastic drop cloths.
3. Carefully remove the vehicle's headliner and interior trim pieces in the roof/roof pillar area.
4. Remove the moon roof/sunroof panel or the assembly. Once it has been removed, inspect the assembly for damage.
5. If equipped, remove the roof drip rail or garnish moulding.
6. Disconnect any electrical or lighting connections.
7. Remove the windshield and back glass.
8. Remove the old roof panel by drilling out any welds along the front, sides or rear of the panel.
9. Mechanically remove any adhesive holding the roof panel to the bows or side supports. Do not cut into the side supports or the roof bows during removal operations. Doing so will alter the structural integrity of the roof.
10. Remove any mechanical fasteners holding the panel in place.
11. Once loosened, remove the damaged roof panel.
12. Carefully clean by grinding or sanding the roof rails and front and rear headers along the windshield and back glass apertures. If the protective coatings are removed on these bows and header areas, they must be replaced prior to proceeding.
13. Make certain that all mounting flanges are straightened and properly aligned with the replacement panel.
14. Trial-fit the new panel.
15. Once in position, test the fit of the front and back glass panels.
16. If everything aligns well, mark the proper position of the panel in several areas so that alignment will be easier after the adhesive is applied.
17. Remove the panel, and prepare all mating surfaces according to OE and the adhesive manufacturer's recommendations.
18. Apply the adhesive, per specifications, at the correct locations, and in the proper thicknesses. Use spacing blocks to insure the correct glue thickness is maintained.
19. Install the roof panel to the substructure, using the marks you made earlier to help align the panel correctly.
20. Securely clamp or use mechanical fasteners as recommended by the manufacturer.
21. Some manufacturers recommend weld bonding or welding in certain areas of the roof panel, in addition to the adhesive. If this is the case with the specific vehicle you are repairing, make certain you perform this operation as well.
22. Apply corrosion-resistant primers and seam sealers as required.
23. Refinish the roof panel area and also the interior as required.
24. Re-install the sunroof/moon roof assembly. Before doing so, however, I would suggest lubricating the tracks with a very small amount of lubricant. Refer to the vehicle manufacturer's specs again here. Some manufacturers require specialized lubricants be used in this area. In fact, sometimes using the improper lube will damage the assembly.
25. Reinstall all of the removed interior and electrical components
26. Buff and polish the painted surface if necessary before final assembly. This tip will help save cleanup time since the glass and moulding are still off the car.
27. Re-install the glass and remaining moulding.
Conclusion: Making the right decision
Remember, this roof panel is going to keep the vehicle occupants safe in the event of an accident. It is important that whatever repair method you perform on a vehicle roof, the roof must maintain structural integrity and the ability to afford protection. By following the manufacturer's guidelines and using common sense, you will be able to perform any type of roof repair with quality, integrity and a clear conscience.
