How to Fix Wheel Well Rust (A Step-by-Step Guide)

When it comes to our cars, rust is analogous to cancer. It causes damage, it spreads, and the sooner you catch it, the better your chances are. But, is there any way to repair wheel well rust once it appears?

Here’s how to fix wheel well rust:

  1. Gather your materials
  2. Remove the rust
  3. Apply Bondo
  4. Sand the cured Bondo
  5. Repaint the wheel well

Rust in the wheel wells can be doubly dangerous because you might not notice it’s there, and it can spread and cause more and more damage over time. Salt and road grime also assault the metal in the wheel well, which can exacerbate the rust. To find out more about removing rust from your wheel well, read on.

Fixing rust in the wheel well.

1. Gather Your Materials

You will need a lot of things for this job, and you have some choices in what you use. Before the actual list, it bears mentioning that while we should always employ safety measures, it’s imperative in this job.

If you’ve ever gotten a metal flake or shaving in your eye, you know how painful that can be. If you haven’t had that experience, you don’t want to, so use eye protection. Sure, you’re always supposed to, but who wears goggles when weed-eating? But you really do need them here. You also need:

  • Several grades of sandpaper.
  • Sander (an electric one or an attachment for your drill)
  • An angle grinder, such as the Bosch 4-1/2-Inch Angle Grinder, will make sanding easier. It’s not a necessity, but will help make larger jobs go faster, and is affordable.
  • The Bondo Body Filler will help the body keep it’s smooth finish. It’s also quick to apply.
  • Spreading knife
  • Wire mesh
  • Primer
  • Paint (see your dealer for matching paint)
  • Clear Coat such as Sherwin Williams Finish 1 Clearcoat
  • Safety Goggles
  • Gas mask

2. Remove the Rust

This is the bulk of the job, will take the most time, and will make your muscles sore, so be prepared. This isn’t a project you do while dinner simmers.

If you’ve got a bad rust problem, you’ll be able to knock it off with your fingers but to get to all the rust (and you have to get to all of it or all this work will be for naught), you’ll need to sand, grind, or cut it out.

With a grinder, attack the big rust spots. In the wheel well, you’ll find some expansive areas that are relatively smooth, and the grinder will work well in these spots. Go at the rust like your car’s life depends on it because it kind of does.

Speaking of the big spots, you have the option of cutting pieces of the rusted metal out and even cutting outside the rust so that you exice the rust and the metal touching it. This works but presents problems sanding out doesn’t:

  • The larger the hole you’ll patch later on, the more difficult it will be to get right.
  • Rust doesn’t form along straight lines, and making jigsaw-style cuts in the wheel well will be challenging to say the least.
  • You may end up having to cut the metal with your grinder (if that’s all you’ve got access to for this sort of job), at which point you might as well grind and sand since the patching job later will be less complex.

Again, the grinder will take on the big spots, but as you get closer to the edges of the rust and encounter nooks and crannies, you’ll need to move to tools with a little more finesse. Use a sanding disk on your drill, or do some delicate work with this Dremel 8220-1/28 12-Volt Max tool. This helps reach smaller areas and offers more precision when sanding. You may even need to hand sand with some sandpaper.

If you take nothing else from this article, take this: you must get every scrap of the rust off the metal for this to be effective.

So grind the metal. Then sand it. Examine it. Sand some more. Look closely at the edges. Sand even more. Don’t take chances, and don’t ever allow yourself to say, “That’s probably good enough,” because if you’re saying that, it probably isn’t.

3. Apply Bondo

Bondo with a capital B is the brand name of an auto body filler, but it’s come to be used for any similar product, so when we say “bondo,” we mean the body filler of your choice and not necessarily the specific 3M product.

When you buy your bondo, it may very well come prepackaged with some wire mesh. If it doesn’t, pick some up (fiberglass mesh will work, too), because you’ll need it to repair the hole(s) you just put in your wheel well.

Attach the mesh with epoxy so it’s behind the hole. Once you’ve mixed your filler, spread it over the hole with the spreader likely included in the package the bondo came in. Keep in mind:

  • Work relatively fast. Once you’ve mixed the bonding agent, you’ve got only a few minutes to work with it before it begins to harden.
  • Spread it thinly and evenly. You can’t fill a hole effectively with more than about a ¼” (0.63 cm) thick layer, so don’t just lather on a bunch of it and hope for the best. If you have a layer of bondo thicker than that, it will crack and eventually fail.

4. Sand the Cured Bondo

This will involve several passes, each with progressively finer sandpaper. The bondo will cure in about 15 minutes, but it may take longer in a more humid environment. Once you’re sure it’s dry, it’s time to sand.

Now, just because step three follows step four doesn’t mean you’re done applying bondo. You may, after sanding some, need to apply some more. There’s an artistic element to the process since you’re trying to mold the bondo to the exact shape the metal that rusted away used to be.

As you sand away the rough spots, and as your wheel well starts to look whole again, you’ll begin using finer and finer sandpaper. When you get to the point of doing what is essentially finishing work, you’ll want to have ultra-fine sandpaper (300 grit or higher), as that’s what you use to get a nearly glossy finish.

The metal of your wheel well needs to be as smooth as possible for when you paint it, so don’t skimp on sandpaper or sanding. An electric sander will make this easier on your arms, but it won’t cut down on the amount of sanding. It won’t take as long, but it’s imperative that the sanding is done to perfection.

Just like we said about rust that if there’s a speck of it left, it will come back and undo your work, if there are any imperfections in the bondo you’ve applied and sanded, the paint won’t stay when you put it on, so make sure you get this part right.

5. Repaint the Wheel Well

Since the rust you cut out and worked to replace was in the wheel well, the paint we use to cover up the bondo job doesn’t have to be a perfect match, you may not need to go to a lot of trouble to match your car’s exact color. And in some cases, there may not be paint in your wheel well at all.

But first, you should apply a primer. Since primer acts like the glue that holds the paint on the car, don’t skip this part. You can spray it on or use a brush, and you can choose whether to do one or multiple coats, but the more coats you use, the stronger the bond with the paint will be.

Another part you don’t want to skip is a breathing mask. Primer and paint fumes are potent, so you should also ensure you have adequate ventilation in the place where you’re doing this work.

Make sure the primer is completely dried, then hit it with some ultra-fine sandpaper to make sure it’s really smooth, then it’s time to apply the paint. Brushing it on is not an option. You need a sprayer for this, and you have to spray the paint on evenly. Apply multiple coats, and then do the same with the clear coat.

Again, since it’s in the wheel well, you might not need a clear coat since not much of the wheel well will be visible.

Once the paint and clear coat have dried, you’re in business. Provided you got all the rust and didn’t use too thick a coat of bondo, your repair job should last a good, long time.

Final Words

It’s not a quick job, but you can fix rust in the wheel well yourself. Be careful and be thorough, making sure to sand well and completely remove all the rust. When it comes to repairing the holes you’ve cut out, be diligent in applying smooth, thin coats of bondo. Finish, sand, and paint, and your repair job is done.




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