Knowing the basics can help ensure a proper repair
Some of the most challenging repairs for a technician are side hits. Side hits with A-pillar damage require a high level of skill and knowledge and will test your patience during repair. Much of the frustration stems from not knowing the exact location to pull the hinge mounts, along with door fit problems. How many times do you re-hang a door to recheck fit during the process? This article will help you with the decision-making process and with technical, how-to help.
Let’s look at the decisions that will need to be made. Do I repair or replace? I-CAR recommended repair procedures for any structural part are “kink verses bend.” A-pillars clearly are structural in nature and fall under a structural component definition. “Kink” is defined as “a sharp bend of 90 degrees or more
within a short distance.” While the term “90 degree” is certainly clear, a “short distance” is somewhat subjective. Using a corner of a note pad or even a paper clip to check the distance is the typical norm. Cracks and breaks that occur while straightening will also determine whether replacement is required. Hidden inner-panel reinforcement damage is also a decision maker. Inner structure damage must be repaired to maintain structural integrity in a future collision and may require removing outer panels to access the damaged inner structure to accommodate repair.
If replace is the choice, can we section and where to section are questions that need to be addressed. Sectioning is an accepted industry standard, unless a manufacturer specifically states otherwise. Remember, an OEM requirement always supercedes a general guideline. Because of the multitude of models, a matrix is impractical. If in doubt, however, the shop must do the research on any vehicle-specific requirements. Check independent sources of technical information, the manufacturer’s vehicle repair manuals or online service information sites. Also, I-CAR’s Uniform Procedures for Collision Repair (UPCR) is available online and is another option. I strongly advise attending the appropriate I-CAR structural repair units as they focus on guidelines, corrosion protection, seam sealing, sound and structural foam application, etc.
Replace with new or salvage? I never minded the salvage because regardless of component damage, everything I needed was supplied. There is nothing more unproductive than opening up a job to find an inner panel that requires replacement was not written in the estimate. Not only did the parts department have problems finding exactly which panel you need, it will have to be back ordered or won’t be delivered for days. Breaking down a frame repair to make room for other repairs is a sure way to lose time and money. Salvage trimming time is greatly reduced by using a plasma torch. Care must be taken to not damage needed inner panels.
When sectioning is the choice, how do we know where to cut? You’ll notice the GM guidelines in the picture (No. 2) highlight cut areas in locations that normally do not hinge and bend during a collision. Natural hinging areas are found at windshield pillar to roof, B-pillar mount around roof and other corner radiuses. Basically, where we see the typical bends from collision damage are areas to avoid. When properly sectioned, the result is a strengthened area, so we stay in areas that do not typically give from secondary pressures to maintain recollision integrity. Remember: never redesign. Also, avoid cutting across hinge mount areas, as this is a high stress area with multiple layers.
Section joints require a sleeve extending 1 in. into the adjacent panel making total sleeve length more than 2 in. This recommendation has changed somewhat through the years due to corrosion concerns. The reduced size allows active (self-healing) rust proofing products to creep under and between these closely installed panels. Allow a root gap distance of three times the thickness of the metal being welded to allow penetration of weld into the backing panel. Install 8 mm/5⁄16-in. plug welds into the sleeve surrounding the weld seam. This distributes the force in a recollision that never over-stresses the weld site, which has been heated from welding. Use caution when making cuts to not cut into inner reinforcements. Remember to never weld continuously. Instead, stitch weld to eliminate overheating and metal destruction. Weld-through primer—once the standard although it may not be required depending on the specific OEM—is applied prior to assembly, followed by epoxy priming after welding is complete. Rust proofing is applied after the primer is cured.
What about fillers found in these areas? Factory application of noise/vibration dampers are often used as shown on the 2002 Explorer A-pillar (No. 5). Some OEM applications are as simple as a bag of insulation stuffed into a pillar, while often we find sprayed expansion foams. It is important to replace noise/vibration dampers with approved foam to minimize rust from moisture entrapment. Some pillars will have rigid structural foam applied by the OEM. These fillers are designed to enhance structural strength and require OEM replacement foam. When encountering structural foam, it is important to clean out existing foam beyond the hot zone created by welding.
Tips on repair: Know where to relocate the hinge areas. Three-dimensional measuring is a key here. When measuring a unibody vehicle, hang targets on the undamaged side for comparison to build the damaged side to comparable points of reference. This may include R&I of the opposite fender to access, however, the time is well spent. By knowing where to pull the hinge mounts, lock pillars and rockers, a great amount of time is saved by not hanging the door for fit checks until near completion. This also allows the work area to stay open to repair. Proper measuring technique will virtually eliminate reinstalling of doors for rechecks as repairs progress. Multiple pulls are also a time saver. If the complete area can be reversed out the way it went in, redimensioning is easier to attain.
What about the full-frame side hits? After setting up the vehicle on a frame machine, using full-frame anchoring, re-center the cab to the frame. This can be confirmed by measuring OEM cab locator holes found in braces and cross members welded to the floor. Once re-centered, comparison measuring from one side to the other is simple. You may need to block the cab between frame and rocker on the opposite side to hold the cab in place during repair.
Use old hinges for attachments to pull from. Welding old U-bolts or flat strap across a hinge face makes a super attachment that allows reversing the damage from the same angle of impact. Loop short chains together allowing for even distribution of pulling force to minimize distortion created from pulling. Just about every door opening that sustains a side hit is shortened up due to buckles and bends. Pull length while pulling width and notice the difference in door fit quality.
Door openings also become out-of-square in height. A-pillars on unibody vehicles may require a downward pull while holding up at the B-pillar and tying down at the rear allowing an up/down correction of pillar height relationship. Often R&I of a rear bumper cover is the only way to access the strength of the rear structure. Truck cabs may require a twist set up to correct pillar heights.
Can inner dash structure be repaired? The Chevrolet Impala is an example of inner structure that will require replacement once collapsed. This structure is a formed die-cast alloy, which when bent will compromise strength. The Pontiac Grand Am offers high strength steel reinforcement comparable to frame rail structure and must be treated as HSLA frame rail repair. As mentioned earlier, all OEM requirements override general guidelines. If a manufacturer says to replace, by all means, replace it. Some of the dash inner structure is integral to passenger air bag deployment and will require replacement if it sustained any damage.
Is it acceptable to straighten inner braces and only replace the outer skin? By straightening the inner structure and only replacing the outer, dash R&I and an involved inner structure replacement process can be avoided. This is very acceptable, unless there is a specific OEM requirement that states otherwise. Not damaging the inner bracing while cutting off the outer panel is imperative.
I understand how time consuming and challenging side hits are from years of repairing sublet structural repairs from other shops. The side hits were often sent out to me in the frame shop so the collision shop could maintain its productivity. I hope my experience can help make your job a little easier.