Sheet Metal Spot Repair

Sheet Metal Spot Repair

Last Updated November 6, 2019 | Meghan Drummond

We’ve all been there. You leave your Mustang parked for a moment, and when you come back, it's clear that someone didn’t prize your perfectly maintained pony car the same way you do. A dented or badly scratched door on an otherwise perfect classic Mustang is enough to make anyone cringe.

Or, perhaps you’ve taken on a restoration job and discovered some dents that aren’t large enough to make you want to replace the body panels but are large enough that you don’t want to leave them as is. Salvage and rebuilt titles in particular often just need a little sheet metal work to repair damage and look their best.

While serious bodywork is best left to the professionals, doing quick spot repairs yourself is a way to get the job done when it’s convenient for you and also save yourself some money. Whether it’s working out a quick dent from someone swinging their car’s door a little too enthusiastically into your own, or a bit of hail damage, there are ways to repair minor dents and scratches at home if you’re willing to do the work.

  • Degreaser
  • Body Hammer and Dolly Set
  • Sandpaper Ranging From 20-400 Grit
  • Painters Tape
  • Primer
  • Primer Sealer
  • Paint
  1. Before getting started, it’s important to make sure your car is clean. It can be difficult to get a true estimate of what type of damage you’re trying to repair if there’s a lot of dirt on your car. Even a little dirt can affect the way light reflects, which can make a large dent look smaller or vice versa.
    Cleaning your car will also make paint matching easier. Damaged Cobra Hood
  2. Remove all wax and grease from the surface of your car. Wax, like the kind you apply to your car, is great for minimizing damage and protecting your paint. Unfortunately, in order to fix your paint, you’re going to have to rough it up first. Wax and grease can also affect the way paint adheres to a surface. Car being thoroughly scrubbed
  3. By figuring out what type of physical damage you’re dealing with, you’ll be better equipped to address it. If you have a ridge that’s being caused by an indentation, then solving the indentation should also address the ridge.
    Another way to think about it is to imagine yourself as a detective. Based on the damage that you see, what happened? Understanding the direction of the impact can help correct it. Bill looking at the front of the Cobra
  4. A body hammer (very different from a claw hammer) and dolly are the most “correct” tools for this step, but there are success stories involving small suction cups and countless other improvised tools. The major thing is to reverse the damage, and to work from last to first, meaning you’ll work around the major point of impact.
    Working from last to first is important to prevent metal from overstretching, which can weaken it. This stage is one of the more time consuming, but working slowly and methodically is the best way to ensure a smooth repair job. Holding a dolly on one side and hitting with a hammer
  5. It’s normal to have a few points that are less than perfect at the end of your reversal stage. During step five, you’ll want to take some additional time to fine-tune this area with a hammer and dolly. Use a straight edge for your contours and a glove for highs and lows.
    One good tip is to let water run down the side (not much, just a dribble) to see how it bends and follows the metal. This can help expose areas that are less than perfect for additional fine-tuning. It is almost certain that you will have damaged your paint during this process, which is what the next several steps will address. If you’re able to pop out a dent without affecting the paint and don’t need plastic filler, then it’s fine to stop here. Hammer and dolly work
  6. No matter how advanced your hammer and dolly skills are, you’ll likely end up with a few small dents that will need to be filled with plastic filler.
    First, you’ll remove paint from the area. A 24-grit grinder is ideal for this job, but you can do it by hand if you don’t have access to that tool. You’ll mix together the plastic filler and hardener, and then apply as smoothly as you can. For application, a longboard with grit paper will work perfectly.
    You never want to apply more than 1/8” of plastic filler. Plastic filler being mixed
  7. Using a dual-action sander and a 120 grit paper, sand around the edge of the plastic (but not the plastic itself). Wipe the area down with a damp cloth and take a moment to appraise the entirety of the work. The next steps all relate to painting and finishing, so you want to make sure you’re not painting work you’ll have to strip and redo later. Sanding down plastic filler
  8. Before you get started with priming, first you’ll want to use painters tape and plastic sheets to make sure that you don’t dribble primer or paint on the rest of your car. Making sure you don’t make a mess is significantly easier than trying to clean up a mess, especially if you don’t notice it until the primer is already dried.
    You’ll apply an etching primer on the bare metal. You should only need a single coat of this, but it’s important to apply. Not only does it make it easier for subsequent layers of paint to attach to the bare metal, but also it helps to protect the metal underneath from rust and corrosion.
    Then, you’ll apply three to four coats of primer surfacer. Paint doesn’t adhere well to bare metal, so this level of priming is necessary in order to get the clean, smooth OEM paint job of your dreams.
    Once the primer is dry, it should be wet-sanded with 400 grit paper. This is a very fine grit and may be difficult to find at a home repair store, but it’s important to get a fine grain since otherwise you may end up with swirls or scuffs that can be seen through the paint.
    You may need to re-prime your surface depending on how well the primer adheres on the first application.
    After you’re satisfied that the area is well-primed and very smooth, you’ll apply a primer sealer. A primered Cobra Hood
  9. To match your factory paint color, check for the code on the inside of the door and then check to see which paint color that’s associated with. Ordering factory touch-up paint can be hit or miss, so be sure to check a small amount of the paint for true matching before applying it to your entire car. You may need to get a body shop to help you precision match your paint, especially if you had a particularly rare or unusual paint color.
    Apply paint as normal. Mismatched body paint
  10. Remove the painter’s tape and plastic sheeting and check over your work. You’ll also want to check the rest of your car to make sure that any overspray is cleaned away.
    Then, you’re finished! Enjoy your newly-dent free vehicle. Cleaned and finished Cobra
Sheet Metal Spot Repair

Whether you're trying to correct a dent or putting in a patch after removing rust, this guide walks you through how to properly contour, sand, prime, and paint your Mustang so that when you're finished it looks as good as new.

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