When is a rust spot a wee bit too big for Bondo? Find out.

Dear Car Talk

Dear Car Talk | Sep 01, 2008

I have a huge rust spot on my car, a '95 Subaru. It is not really a rust "spot," but rather a missing part of my car that has rust around it. I tried to sand it down and put Bondo on it and repaint the car, and it actually looked pretty good for a while! As impressive as my Bondo job was for a first-timer, the Bondo soon fell off, and now the huge rust hole is back. I am wondering if there is any other option besides replacing the whole part of the car. Thanks so much. -- Shannon

RAY: That's interesting, Shannon. You have a hole in your car with a little bit of rust around it. My brother has a big pile of rust with a little bit of car around it!

TOM: Well, the first mistake you probably made was not removing the rust completely. Bondo is pretty amazing stuff, and it'll stick to just about anything. But if you left some rust around the edges, the edges would continue to corrode, and the patch job would eventually fail. As it did.

RAY: So, you have to sand the area surrounding that hole down to bare, shiny metal. Then, what body shops will do is they'll tack-weld a piece of sheet metal over the hole and hammer it in so it's somewhere between flush and concave. Then they'll grind down the welds so nothing's sticking up. And then there's actually some BODY there to do WORK on!

TOM: Well, we should clarify: That's what body shops do for old heaps like yours, Shannon. If this were a 2005 Subaru, they'd just replace the whole panel.

RAY: But you don't need it to look perfect. It's an old car. You just want to keep it from looking decrepit.

TOM: I suppose it's too late to do that for my car?

RAY: Way too late. Anyway, if you're handy, Shannon, you can add the sheet metal yourself, then slap the Bondo over that and paint it. That should hold.

TOM: Or you might be able to find a local body shop that'll weld on the metal for you, and then you can do your Bondo art, at which I'm sure you're now an expert.

RAY: The other thing you can do -- which I've done on some of my old cars -- is just take a larger piece of sheet metal and rivet it right over the whole area. Then you paint it, and from 500 yards or so, at night, it'll look good as new.

TOM: Actually, I like that idea. The "rugged, armor-plated" look is in these days. You may like that so much, Shannon, that you'll want to do the same thing on the other side!

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