Wednesday, 30 April 2003 10:00

Expert critiques Modern Collision Rebuild

Written by Dick Strom

In two recent articles, I spoke with Mark Olson, owner of Future Forensics www.futureforensics.com, and part owner of Verifacts Automotive, businesses specializing in automotive damage investigations. Olson exposed a number of common mistakes that could easily land shops in legal hot water, even bankruptcy. Olson keeps up on the latest changes from manufacturer service bulletins, and knows first-hand, having supplied "expert witness" testimony at many auto-related court cases, how juries, unfamiliar with the intricacies of collision repair, render judgment. So, when Olson (an I-CAR instructor, former insurer representative, and former shop owner) offered to take a critical look my shop's repairs in progress, to point out what we're doing right and wrong, I accepted. 

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To ensure Olson's review would be as candid and unbiased as possible, we didn't inform our techs that he was coming or the reason for his visit until after he'd arrived. The purpose was to learn how to produce a better product, not to criticize. What we learned, we'd like to pass on to you for your consideration. How would your shop fare
Use epoxy primer under seam sealer

Olson first checked our paint and repair departments to see if they were using a primer around welded areas that is compatible with seam sealer. He explained that seam sealer, applied around welds to prevent rust from starting, prevents acid etching primers, when applied beneath it, to "breathe." "The use of epoxy primer underneath seam sealer affords longer lasting corrosion protection than the acid etching primers most shops are still using. Acid etching primer underneath seam sealer is more likely to cause premature corrosion and resultant lifting of the seam sealer, possible grounds for a Diminished Value (DV) claim and expensive re-dos.

Newly welded panels must be seam sealed on both sides (anywhere moisture can reach welds) at the panel seams. Though this may result in a look that is somewhat different than originally manufactured and it might look 'repaired', you've returned it to factory corrosion specifications, and so the resultant differences from original will normally be considered inherent DV, not repairer-related DV. And never use seam sealer over bare metal." He also checked our techs bays to be sure they weren't using acid etching primers, which they were not.

When to replace strut towers and other structural components

Olson next examined a right front quarter hit on a newer Subaru wagon, still mounted on a frame rack. In the damage, including front suspension, hood, right front fender, core support and aprons, the right front strut tower had been forced up somewhat out of specs. Olson agreed that the course we'd taken - sacrificing the damaged front apron in order to draw the tower back into specs - was the right course of action in this particular case. "Whenever possible and practical, keep the original strut tower intact."

Next, we moved to a Honda that had been somewhat side-swayed to the left, resulting in light damage to both front aprons and upper rails. Rough-out of the front structure had been done, the damaged core support removed, and both aprons straightened. But a problem yet remained; though the aprons straightened out well, there was still slight damage to both upper structural rails, and there was no way to access the remaining gentle bends in the box structures without removing the aprons covering them. "Because of the way this vehicle is manufactured, there's no way to return this structure completely back to the way it was manufactured without removing the aprons for access; the crush collapse zones built into the upper rails have been damaged and, though that damage appears to be slight, it would be weak spot in a future accident.

Keep in mind that a front structure not being returned to manufacturer tolerances and engineered strength affects the airbag timing, which relies on the crushability of the front of the vehicle. If the car is not back the way it originally was manufactured, the airbag won't work correctly because the airbag sensors depend on factory engineered crushability to function as designed. You have sensors out here on the front of the car and you have sensors under the dash that are timed to work together. The one inside is set lighter than this one so they close at the same time. If you make this front structure weaker or stronger than originally manufactured, the sensors won't close at the same time, and the airbag won't deploy. We're talking critical crushability here, that could have expensive, even deadly results if repaired improperly." Preparing panels for welding and limited use of weld-thru primer

On this same Honda, Olson notes, "The tech has jigged the core support in place, and before fitting it he used a Rolox pad to remove the original E-coat sealer from the welding contact locations on the backside of the new core support. Remember that products like Rolox pads may remove the sealer, but won't remove the zinc coating on the metal. And weld-thru primer won't stick to the zinc under the E-coat. The truth is that you don't need to use weld-thru primer if you have a zinc-coated panel. So, instead of removing factory E-coat at the mating surfaces, drill the new panel at the exact locations of the original welds, and scrape the E-coat off with a scribe through the plug-weld holes before welding.

Research over the past year or so has found welding through weld-thru primer makes a weak weld because weld-thru primer doesn't strike the arc well, creating poor penetration. And the zinc in the weld-thru primer combines with the weld, making the weld weaker. Now, if you drilled out a panel and you had to grind it through the zinc, for whatever reason, you may use weld-thru primer there, but again, once it's all fitted together, clean the weld-thru primer from the welding area through the plug-welding hole first. The rules change, but in court you will be held to those rules that existed at the time you repaired the vehicle. At this point in time manufacturers are saying 'preserve the original E-coating as much as possible'.

"If, for instance, you're replacing two or more new adjacent panels at the same time, the procedure would be to punch or drill your plug-weld holes in the same locations as those in the panels you removed, jig it all together, clamp it in place, and once you're happy with the fit, scratch the E-coat out with a scribe through the plug-weld holes, before welding it all together. Daimler-Chrysler recently stated that shops should not use weld-thru primer on anything on any of their cars, period."


Incomplete welds are weak welds

Our techs joined him underneath a pickup bedside we'd just installed. Olson pointed out what he described as an all too common welding problem in shops - one that results in many failing the hands-on portion of their I-CAR welding certification test - the problem of incomplete welds. In this particular instance a tech had not completely filled in some of the underside plug welds attaching the bedside to the box. "Always start plug welds at the center of the plug weld hole, being sure to attain full penetration. Then spiral your weld out from that point until the hole is completely welded shut. Many techs, in a rush to get on to the next weld, or through carelessness or lack of welding education, don't take that extra second or so needed to complete each weld in its entirety. And the result could be welds some of which tear loose in a subsequent accident, because that minute portion not attached by weld to the base metal is the weak link in that weld. And enough weak welds, especially in structural areas of a vehicle, can affect crash-ability and airbag response."

Plug vs. squeeze-type resistance welding When one of my techs asked what procedure would be best when using squeeze-type resistance spot-welding, Olson replied that resistance welding is okay on some vehicles, but not on others. "Right now, Ford and GM are reconsidering collision shops' use of it, but Chrysler says don't use it on their vehicles unless you're doing a weld-bonding process, which is different than squeeze-type resistance spot-welding. But keep up to date with the recommendations of auto manufacturers. Basically, Ford, GM, and Chrysler don't recommend the use of squeeze-type resistance spot-welding, though Chrysler is now saying you can do it if you go through the glue, but only in certain applications. The rules change, so protect yourself by keeping current with them" and keeping detailed records of repairs and communications.

Olson posed the question, "So, how do you avoid using weld-thru primer if you are grinding flanges? First, don't grind flanges. When you're drilling out spot-welds, the goal is to wind up with weld 'nuggets' (that portion that remains of the original spot-welds). The challenge is to put the new welds through the new panel exactly in the same place as the old welds that were removed. So if, after you remove the damaged panel, you grind down flat only the old weld nugget itself without grinding surrounding metal, and then put the new weld back in exactly the same spot, weld-thru primer won't be necessary. That's what Chrysler is saying to do. If you don't replace the welds in the same locations as the originals, and do use weld-thru primer, you take on the liability for the repair!"

What are "re-inspection companies" looking for?

When asked what specific things 're-inspection companies' would be looking for, Olson answered, "They're looking for any panel that was repaired when it should have been replaced, lack of cavity waxing and seam sealing, and the like. If, for instance, a 're-inspection company' notices that a shop used weld-thru primer on, say, a Chrysler, that wouldn't necessarily be grounds for re-repair. But they're going to be looking for a pattern of other things, such as an absence of seam sealer around welded areas, poor quality welds, and things like this to focus on. With the car elevated, they'll be inspecting all repaired and replaced panels to see if they're welded properly, even checking inside rails and other cavities with small mirrors. They'll also be looking for proper seam sealing, cavity waxing, and epoxy priming all the way around all welds. Any potential for future corrosion is a prime focus of re-inspection businesses. Remember, it takes oxygen, moisture, and steel to make rust; the goal in cavity waxing and seam sealing is to keep any and all moisture from reaching the weld area. And the area needs to be epoxy primed after welding and before seam sealing, because if the panels are epoxy primed before welding, in the welding process the epoxy primer is burnt off. And, as we discussed before, seam sealing over acid-etching primer will trap solvents beneath the seam sealer, causing it eventually to lift the seam sealer, allowing rust to start."

How courts view bad repairs

The question was brought up, "If the insurer refuses to pay for replacement of, say, these Honda front aprons, how can the shop get paid to do it right?" Olson responded, "The reality concerning straightening a panel that should have been replaced is that you've lost the structural integrity of the part, and if you agree to do anything incorrectly, you take on the liability for a potentially unsafe repair. The same insurer that wants you to cut corners, when it comes to an issue of liability, will tell the court, 'I don't know the correct procedure because I'm not the technician. I rely on the shop to tell me what needs to be done.' A re-inspection company might say it's the insurer's fault, but if it goes as far as a court of law, it becomes your fault, because you, not the insurer, are the expert. The insurer will convince the jury that they just write the checks to cover whatever the repairs cost, even though their representative may have told you they're not paying for certain needed procedures and parts when you informed him of their necessity.

Reducing shop exposure to repairer-related DV

"So, to keep out of (the aforementioned) blind alley, it is necessary to contact the customer and explain that you can't get the repair right without that for which the insurer refuses to pay. You should explain logically that (using this Honda as an example) 'these upper rail box-construction structural parts are damaged,' and then demonstrate that it is impossible to get inside that welded box to straighten it without removing and replacing mating panels. Give the 'bent pop can' demonstration to prove why the tweaked panel will never regain its original strength, and must be replaced. A customer is not going to allow the car to be 'hacked,' and will be informing the insurer of that fact. Normally, if you've informed the customer but the insurer still refuses to pay for proper repairs, and the customer later turns in a diminished value claim, it will be considered insurance-related DV, not inherent or repairer-related DV, because you disclosed it to the vehicle owner. If, on the other hand, you don't inform the vehicle owner of the problem because you don't want to make waves with the insurer, it then remains repairer-related DV.

Documentation is everything, so write it all down and keep it in your files. And if doing the job right totals the vehicle, let it total. In today's legal climate you can't afford to repair a car improperly, because in doing so you take on the liability. How many cars can you buy back before you have to say, 'I'm in the wrong business?' And if you run the risk and end up having to buy back your improperly repaired vehicle, when you resell it you have to disclose it has been improperly repaired, which makes it basically worthless. Just because a vehicle is brought back into specs doesn't mean it's crush zones are back to the same state and shape as original. Again, the goal in any repair is to put the vehicle back in the same state and shape as it was prior to being damaged, so that it will react the same way in the next collision as it did in this collision.