What should I do about rust on my car?
July 4, 2012 8:30 AM   Subscribe

[CarFilter] My car is developing some fairly bad rust around the wheel wells. The cost to repair it is prohibitive - what should I do?

I own a 2006 Mazda 3 that is otherwise in great shape - only about 82,000 km, runs really well. I bought it used two years ago. Not being an experienced car buyer, I didn't notice that there was probably already some rust around the back wheel wells on both sides that had been painted over. Now one side is rusting slightly, and the other side is rusting fairly badly (Ontario winters are not kind to cars).

Both the dealership and a recommended autobody shop have told me that for the bad side I would need to replace that piece of the panel, at a cost of between $1,200-$1,500, which is frankly considerably more than I'd like to spend on this. They've both said that the rust is too close to having eaten through the panel to simply sand it down and treat it.

So, my question is what I should do at this point. As I see it, these are my options:
1. Pay whatever it will cost to deal with the rust, given that the car is otherwise in good shape (technically I can afford to do it, but it would hurt financially).
2. Sell the car privately now before the rust gets worse and hope that I can still get a good price for it (bearing in mind that I've never sold a car before).
3. Trade the car in for something else before the rust gets worse.
4. Leave it as is and just continue to drive it for another few years, ignoring the worsening rust problem.

I'm sure there are potentially other options I'm not aware of (in case it's not blatantly obvious, I don't know much about cars and autobody work - this is the first car I've owned, and we bought if used from a dealership where a friend works). Any insights into these options and what the best course of action might be?
posted by sabotagerabbit to Travel & Transportation (11 answers total) 5 users marked this as a favorite
Here's what I would do as a better option than 4:
  1. Sand down the rusty bit to bare metal. A flap disk in an angle grinder is awesome for this and a cheap 4 1/2" grinder can be had for $40 or less from Princess Auto.
  2. Use some POR-15 stabilizer as directed by the label.
  3. Skim coat the perforated area with some fiberglass putty. If a big chunk of metal is missing the spray insulating foam you get in a can makes a good backer for the fiberglass (apply a bead from the wheel wheel side) and can be easily shaped with a knife and a sanding block.
  4. Sand down the Fiberglas as smooth as you can.
  5. Mask off the area (try to follow a body crease if you can, helps to hide the difference in colour) and spray the repair with the touch up spray paint you can get from Canadian Tire.
  6. Top coat with some clear.
These steps will a) look better than rust b) help slow down further rusting c) cost $100 tops plus your labour. The more time you spend smoothing and sanding the better the result. The rust will come back in a few years so this isn't a permanent solution.
posted by Mitheral at 9:04 AM on July 4, 2012 [12 favorites]

We did Mitheral's option on our car and it worked out wonderfully. I would feel awfully silly getting rid of a car just because it's about to have some rust-through. Even if you get rust-through, you can Bondo it.
posted by dunkadunc at 9:33 AM on July 4, 2012

You might try complaining to Mazda about this -- some sort of national customer satisfaction hotline, not the dealer. Severe rust on a car of that age seems indicative of a manufacturing defect.
posted by jon1270 at 10:02 AM on July 4, 2012

If you follow Mitheral's advice, PLEASE wear goggles while grinding metal. Metal shards in the eyeball are no fun at all. I know from personal experience.

You probably ought to wear a dust mask while sanding fiberglass, too.

Grinder tips: I know a lot of metalworkers who take the guard off grinders. They have a lot of scars on their hands, and usually at least one significant gash at any time. You'll be tempted to use the edge of the flap wheel--it's so quick, and feels much easier to control a small surface. This will chew up and destroy your flap wheel in no time at all. Using the surface will make your wheel last considerably longer.
posted by mollymayhem at 10:34 AM on July 4, 2012 [3 favorites]

Response by poster: Thanks for the advice so far.

Jon1270: Because we only bought the car two years ago, we have no idea how this started in the first place, and could have been because of something the previous owners did. Otherwise I'd definitely at least try that!

For those suggesting we fix it ourselves: I'm definitely open to that option, but have a couple of follow-up questions. First, will we be okay to do it outside, rather than in a garage? We don't have a garage (and park on a street, but there's a big mostly empty parking lot across the street and we could work on it there). Secondly, does anyone know of any decent resources online that would walk us through the steps a bit? My partner and I are comfortable working with tools but haven't done much of it and don't own anything at this point that we would need...
posted by sabotagerabbit at 10:40 AM on July 4, 2012

And if Mitheral's excellent solution is too much work in the short term, you can put POR (paint over rust) directly on the rust with zero prep to inhibit more rusting.
posted by zippy at 10:42 AM on July 4, 2012

Mazda3's are known for this, unfortunately.
posted by smitt at 11:53 AM on July 4, 2012

ALL Mazda cars are known for being unusually susceptible to rust. It has been that way for years.
posted by twblalock at 1:41 PM on July 4, 2012

It might be coming from the inside out, in which case sanding down to bare metal means you'd end up with a hole. Beware. I would take it to a body shop with a good rep and see what they say before starting any home remedies.
posted by gjc at 4:23 PM on July 4, 2012

The cheap way that doesn't last (but would look good for a while, definitely good enough to sell it):


You can use a spray can for the paint if you aren't picky about the way it will end up looking. Otherwise, you'll need a spray gun. Or you paint the entire car with rustoleum (yes, you can roller it on, search google, the end result is less terrible than you'd think).

The right way will involve cutting out the affected panel and welding in a new one. Not only somewhat expensive, but labour intensive, not to mention you'll need a welder (a small one should be fine) and knowledge on welding.
posted by shepd at 4:35 PM on July 4, 2012

First, will we be okay to do it outside, rather than in a garage? We don't have a garage (and park on a street, but there's a big mostly empty parking lot across the street and we could work on it there

This is very outside doable as long as it isn't raining or too humid (I've always done this sort of work outside in my driveway). All the material drys/cures fairly fast. The sanding and fiberglass work generates some messy waste so if you are doing it in a public place lay down a drop cloth and have a broom for clean up afterwards.
posted by Mitheral at 8:26 AM on July 5, 2012

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