Fitting new parts

According to I-CAR’s Snapshot of the Industry report, R&R bolt-on parts is the top trait in which a shop expects an entry-level employee to be proficient. It is also one of the first things that a customer will check. As the customer is escorted to examine the newly finished repair, its “Fit and Finish” is what is most easily seen and evaluated from afar (see Fig. 1).

Research had discovered that people make up their mind in seconds whether they will like your work. In sales, it is said that a customer will make this decision in the first 45 seconds. It follows, then, that if the fit and finish is not good as the customer approaches the vehicle, they will not be satisfied. Even though a vehicle is checked at every point of repair and a poor fit will be discovered and corrected, it remains one of the most critical parts of the repair.

In spite of its importance, the task of replacing bolt-on parts is often given to the most junior worker in the shop, sometimes without even the simplest guidelines as to what is considered correct for that make and model, since the shop “expects” the new hire to know it. But the many evaluation details take practice and experience.

You might notice that as a seasoned worker walks around a vehicle, he or she will instinctively look for things such as gaps, positive and negative flushness, and opening and closing effort. This technician will question whether the misalignment extends past just the bolt-on parts into a structural area, and therefore need structural alignment, whether the fender will hit the door as it opens, and whether the undamaged side is truly undamaged. Yes, all these items should have been caught and noted in the damage report, but from time to time such details slip by — and if we are to expect a good fit, they will need to be evaluated. All in all, it is not an easy task.

For those who have been in the collision repair industry for a while, the thought of checking a service manual for the proper gap may not be the first thing that comes to mind. This is because in the not-too-distant past, this type of information would not have been in the manual. Even today, not all gaps will be available, but many of today’s manuals do have them — and can be easily checked from your computer or smart device.

Removing damaged parts
Even before a part is removed from the vehicle, taking a quick walk around is very helpful. Check the undamaged areas of the vehicle for gap size and uniformity (see Figs. 2 and 3). A homemade gap gauge can easily be made from a paint stick, adding tape to it to match the undamaged side’s gaps (see Fig. 4).

Also check for flatness — either negative or positive — and ease of opening on the undamaged parts. These areas should act as a reference for replacement parts.

Use a flat hand or a credit card to check for positive or negative flushness (see Fig. 5). The doors, hood, hatch and other openings should be operated and checked for smoothness or misalignment — all of which should be checked before the old damaged part is removed. If additional damage is noted, a supplement should be prepared.

As the old part is disassembled, the fasteners should be “bagged and tagged” to help with reassembly. Replacements for fasteners that are damaged should be ordered as the vehicle is disassembled, when there is sufficient time to get new ones in before assembly. If any unusual wire routing or attachments are noted — how many shims are present, for example — take a quick photo with a smartphone (see Fig. 6) so you can have it for reference when reassembling.

You may be tempted to throw the bolts in the top of your toolbox or workbench, knowing that you will surely remember how to put a simple replacement part back on. But as time passes, things can become lost or misplaced, and memory fades rapidly. That’s when a tagged bag of parts and photo can come in handy. Some shops even have the estimator or shop foreman mark the vehicle as “Repair” or “R&R,” to speed things up (see Fig. 7).

Mind the gaps

During the initial inspection, the vehicle should be checked for structural damage. Even in minor collisions, a vehicle’s shape can be misaligned. To visually check this, all the gaps should be checked to determine whether they are consistent over the entire vehicle. Gaps generally are from 2 to 8mm, with steel panels having the smallest gaps and plastic and aluminum panels needing more room for terminal expansion.

The gaps on all doors, hoods and deck lids should be even on all sides, and they should open and close with ease. If they bind, it means there may be structural or alignment problems. Doors should smoothly align and close over the striker plate without effort — and without needing to be raised to close. On older vehicles, the hinges should also be checked for bushing wear, which is likely not a result of a collision.

Flushness

Not all panels are mounted flush. In fact, many manufacturers recommend a slight positive flush

mount (0 to 2mm) for forward parts such as fenders to help with wind noise and moisture leaks (see Fig. 8). As the wind passes over the forward-mounted parts, it does not cause a turbulence or noise as it hits the next panel. Also, some fenders must be mounted a bit positive so that as the door opens, it will clear the fender. Often in even minor collisions, as the fender is moved back even slightly, the now-narrowed gap renders the door inoperable. As the occupant tries to get out and force is applied, the fender incurs additional damage.

Structural vs. Panel Misalignment

If structural misalignment is suspected, the vehicle should be measured to determine whether

corrections need to be taken before trying to fit the new part. Even with adjustments built into bolt-on parts, a structural misalignment, however slight, will make it impossible to align the new part. Examples of this include elongated holes (see Fig. 9) for forward and aft movement, or large square holes (see Fig. 10) for movement forward and aft, as well as inward and out.

The types of adjustments come in many forms, such as slotted or elongated holes (Fig. 11), large square holds (Fig. 12), J-clips (Fig. 13), shims (Fig. 14), and adjustment stops, just to name a few. These are all used to fine-tune a vehicle’s alignment as new parts are being assembled.

Attaching the new part
Once the vehicle is checked for proper structural alignment and the adjacent panels are checked and protected from damage (see Fig. 13), the new part can be dry-fitted. This step becomes particularly important if the shop paints the parts off the vehicle, then assembles the completed work. Once the part is sent to paint, when it comes back its attachment must be easy and without binding and scraping, so as not to damage the fresh paint.

When checking alignment, the old attachment marks can help. If the new part is put in place, it is likely that it should be attached where the previous part was placed (see Fig. 14). When aligning a new part, start the bolts loosely in their holes. Then tighten them — starting where the vehicle is stationary, such as at the rocker, where there are now movable parts. Move up to the A-pillar, where the door may or may not be aligned correctly.

Next, move down to the front, and tighten the bolts at the front by the

hood. Note that the bolts are only lightly tightened (except for the rocker bolt) because it may be necessary to loosen them and adjust the gaps and flushness as all the pieces come together. When fitting large parts such as hoods, get a fellow technician to help as they are first put in place (see Fig. 15); you can fine-tune them by yourself later.

With the new panels now in place and the mounting bolts lightly tightened, you can now begin the fine-tuning. Start where the adjacent panels are stationary, moving to where there are a number of movable panels — such as the core support, where fenders, header and hood all may need to be aligned. By aligning the simplest ones first, it is likely that the more difficult ones will be easier to do. Check gaps, flushness and ease of operation. When the alignment is complete, all the bolts should be final tightened.

Although the explanation above is for a fender, all bolt-on parts should be fitted from an area where it is least difficult to align. Stationary parts provide a starting point; you can then progress to areas where multiple movable parts come together.

Special attention should be given to openings such as doors, hood and deck lid. When fitting an opening, the striker or latch should be removed and the part fitted before the latch is adjusted. That is, the part should be adjusted to the opening, with the latch being adjusted to the fitted part. If the latch is in place as the opening adjustments are attempted, it is much more difficult to complete. Technicians doing it that way have been known to struggle for hours before final adjustments are completed (see “Tech Tips,” below).

So let’s recap: If attaching bolt-on body parts is one of the top required skills needed for an entry-level technician, and parts replacement is often given to the most junior person, this must mean that it is a simple task, right? Well, like many things in life, “if you know the answer, the question is simple.”

With repetition and experience, swapping parts can be a simple task for the technician. But every so often, it can also kick you square in the … toolbox. As with many tasks, success won’t come without some effort. Developing a system, having a mental checklist, observing, evaluating and revising your system as needed — all will help to make a deceptively simple-looking job easier.

Tech Tips

• Verify and inspect new parts.

• Protect adjacent parts.

• Dry-fit before sending to paint.

• First fit from the stationary adjacent part, then forward and rearward, inward and outward, and finally upward and downward.

• Use the undamaged side as reference.

• Use old location marks as references.

• Remove the striker or latches before fitting openings.

• Use a gauge (even a paint stick works) to check side-to-side gaps.

• Sight down the gaps for evenness (rockers, hood, etc.).

• One telltale sign that a door may have been damaged by a fender hitting it is paint damage on the edge of the door. If found, expect that the door may need adjusting, along with the new fender.

• Don’t final-tighten the fasteners until all adjustments are completed.

Controversial fitting techniques
Although unibody vehicles are flexible and may sag when a fender is unbolted, using a floor jack under the fender rocker to flex the upper door fender gap or under the bumper mount to tighten the gap may be a mistake. If a vehicle is resting on its suspension and the gaps are not even, there may be structural damage — and it should be corrected before fitting the fender.

Jacking the core forward to get proper forward fender adjustment may also be a sign of structural misalignment, and measurement may be necessary.

If parts must be forced to obtain alignment, something is wrong. Look for what is causing the difficulty, and correct it. If force is used and the vehicle is subjected to normal road vibrations, all of your hard work may be lost.

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