Fender and Quarter Panel Repair in Yorba Linda

Starting from the tire and working outward: the fender skirt is usually destroyed, the sidewall skin above and behind it is torn or debonded, the substrate behind that skin is opened to water, framing members in the bay may be bent or cracked, and anything routed through the bay is at risk. That includes 12 volt wiring, water lines, propane lines on some layouts, and slide out seals.

The reason this matters is that blowout damage on the outside looks like a fender problem. The owner sees a missing skirt and a torn section of skin. What they do not see is that the substrate is open, the framing has taken a hit, and the wiring loom in that bay has been beaten against the frame.

Our assessment on a blowout always includes opening the bay rather than assessing from outside. It costs a few hours and it is the difference between a repair and a repair plus an electrical fault three months later that nobody connects back to the tire.

• Fender skirt destroyed or torn from its mounts
• Sidewall skin torn, punctured or debonded above the arch
• Substrate opened to water intrusion behind the torn skin
• Framing members bent, cracked or separated in the wheel bay
• Wiring, water lines and LP lines routed through the bay
• Slide seals, skirting and underbelly material torn away
• Adjacent axle, spring hanger and brake components impacted

It depends on construction, and RVs use several. Motorhome wheel flares are usually moulded fiberglass bonded or fastened to the sidewall and repaired as fiberglass: grind out the damage to a V, laminate from behind where access exists, fill, shape and refinish. Trailer fender skirts are frequently formed aluminum or moulded plastic and are more often replaced than repaired.

Where the flare integrates into the sidewall rather than bolting to it, the repair extends into the sidewall by definition, and the blend goes with it. This is another case where the refinish area is set by where a legitimate break exists rather than by the size of the damage.

On vans and trucks, quarter panels and fenders are conventional metal work. Steel and aluminum are worked back toward shape, sectioned where the metal is torn or work hardened, and finished. The wheel arch lip is the area that matters most, because a lip that is not correct in profile shows against the tire from every angle.

Because the arch is where moisture, road salt and abrasive debris are constantly thrown at a joint. On steel bodies the lip is a folded seam that traps moisture between two layers, and it rusts from inside the fold outward. By the time bubbling appears in the paint, the metal behind it has been going for years.

The failure of most arch corrosion repair is treating the visible bubble. Cutting out only what you can see leaves the rusted metal inside the fold, and it returns within a couple of years looking exactly as it did before. Proper repair means opening the seam, removing material well past the visible edge until sound metal is reached, then rebuilding the lip and treating the interior surface before it is closed.

On aluminum bodies the equivalent problem is galvanic corrosion where steel fasteners meet aluminum panel, which produces a white powdery deterioration around every fastener in the arch. That is repaired by removing the affected material and reinstalling with correct isolation between the two metals, not by sanding and painting over it.