Body Rot Repair

Car-Nation’s Leo Hovel began the job with a 36-grit sanding disc on a small air grinder. What looked like a few easy-to-patch bubbles proved to be rust all along the bottom edge of the quarter, which had been covered with body filler. The grinder almost always reveals about twice the problem you had anticipated.
Car-Nation’s Leo Hovel began the job with a 36-grit sanding disc on a small air grind
Once we decided to cut out the rust and weld in a new patch panel, Leo used masking tape to mark the cut line. By removing as little metal as possible, the repair would not be visible from inside the trunk (it was below the level of the trunk floor) and a crucial bodyline would not have to be reconstructed.
Once we decided to cut out the rust and weld in a new patch panel, Leo used masking tape t
In addition to slicing along the taped line with an air-powered cutoff wheel, several factory spot-welds also had to be drilled. The secret is to drill only the weld and the first layer of metal, leaving the second layer intact so that you can weld to it again later.
In addition to slicing along the taped line with an air-powered cutoff wheel, several fact

At the bottom edge of the quarter is a pinch-seam where the inner and outer sheetmetal is welded together. A hammer and chisel can be used to separate the two, but an air chisel (use earplugs!) will be cleaner and faster. Check out all the rust and crud that fell out! We even collected 32 cents.
At the bottom edge of the quarter is a pinch-seam where the inner and outer sheetmetal is
Fortunately, the inner half of the quarter-panel wasn't rusted too badly. Also, note the hole where the plug goes for the factory trunk drain. Year One sells new plugs, and patch panels for the inner quarters. We didn't need them, so Leo thoroughly grinded off all the surface rust and sprayed the area with 3M Weld-Through Coating to prevent rust from coming back.
Fortunately, the inner half of the quarter-panel wasn't rusted too badly. Also, note the h
Bummer: Year One doesn't make patch panels for Dusters, and we didn't want to buy full quarters just to get the lower rear patches. The solution was to make do with spare sheetmetal, and Leo found a similarly shaped piece in a Jeep Grand Cherokee fender. If you're in the same predicament, another solution is to buy a rust-free panel cut from a similar car--there are many wrecking yards in the Southwest that will mail 'em to you.
Bummer: Year One doesn't make patch panels for Dusters, and we didn't want to buy full qua

While it's best to get donor sheetmetal that's as close to the right shape as possible, still expect some fitment work. Leo added the pinch-seam flange to the bottom of the panel by tapping it over a straightedge, and then drilled holes in anticipation of spot-welding it back in place. He also sanded all the old paint off the panel and sprayed it with Weld-Through Coating to ensure good adhesion of the new paint.
While it's best to get donor sheetmetal that's as close to the right shape as possible, st
The fit of the new panel was great! Vise-Grips and welding clamps were used to hold it in position for welding. We've seen some custom shops butt-weld the new sheetmetal to the old, but it's a tough technique for beginners. Instead, Leo overlapped the new metal behind the original quarter-panel and slightly flanged the top edge of the repair panel to bring it flush with the level of the original metal. Doing so assures that not too much body filler will be required to hide the repair.
The fit of the new panel was great! Vise-Grips and welding clamps were used to hold it in
As is always the case with sheetmetal, you don't want to weld too much at a time because that will heat and warp the repair. Instead, Leo placed tack-welds several inches apart, let the metal cool before adding more welds, and continued the slow process until the entire seam was attached. After each spot-weld, a body hammer was used to tap down the sheetmetal while it was still warm. That prevented the welds from creating high spots that would need to be repaired.
As is always the case with sheetmetal, you don't want to weld too much at a time because t

This view from inside the trunk shows that the body hammer was backed with a prybar because a dolly would not fit into the crevice at the edge of the trunk.
This view from inside the trunk shows that the body hammer was backed with a prybar becaus
It wasn’t practical to patch the entire repair with a single piece of sheetmetal, so a second piece was used to repair the rusty portion where the inner and outer quarter-panel sections were spot-welded behind the bumper.
It wasn’t practical to patch the entire repair with a single piece of sheetmetal, so
Once all the welding was done, a 36-grit disc was used to grind all the welds down to the level of the original sheetmetal. Again, care must be taken not to overheat and warp the metal while grinding. The pointed end of a body hammer can also be used to tap down high spots in the welding.
Once all the welding was done, a 36-grit disc was used to grind all the welds down to the

Here's the repair after all the welding and grinding was done. Next comes the part requiring even more skill. When we asked Leo about the finer points of the application and the working of the body filler, his answer was, "You have to have experience." Practice a lot.
Here's the repair after all the welding and grinding was done. Next comes the part requiri
There’s no getting around the fact that this type of repair is going to require some plastic body filler. Mix the filler according to the directions on the can, making sure to prepare it on a clean surface and to use a clean spreader. Add the filler in smooth, even strokes, making sure there are no air bubbles. It will seem like you’re adding a ton of filler, but most of it will get sanded off.
There’s no getting around the fact that this type of repair is going to require some
Leo began the smoothing process using 80-grit paper on an 8-inch dual-action sander set at a very low speed to avoid removing too much material at once. This step takes more time than you’d expect, but as you shape and feel the repair, you’ll see that you’ll remove all but a thin film of the body filler.
Leo began the smoothing process using 80-grit paper on an 8-inch dual-action sander set a

As the repair takes shape, high spots will be revealed by shiny metal; low points (arrow) will be spots that are sanded less than the surrounding area. The difference between a high and a low spot will barely be discernible to the novice eye and hand, and it takes a lot of sanding skill and experience to get this part right. The high spots can be lightly tapped down with a body hammer, but the low spots may require more body filler.
As the repair takes shape, high spots will be revealed by shiny metal; low points (arrow)
After judging the repair, Leo decided that there was one low spot requiring more filler. For the second application of filler, make sure to cover the entire area with a thin coat. If you only add filler to the trouble spot, there’ll be a seam in the texture of the body filler where one layer ends and another begins. It’s easier to smooth the entire layer than to try and blend a second layer of Bondo to the level of the first.
After judging the repair, Leo decided that there was one low spot requiring more filler. F
Once the second application of filler had been cut down with 80-grit and the DA sander, more finish work was done with 80-grit on an air-powered longboard. Leo used regular black spray paint as a guidecoat; the layer of black makes it easier to discern the high and low spots while sanding. At this point, any flaws in the repair should be minor and easily repaired with sanding. If further hammerwork or extra filler is needed, it means you weren’t thorough enough in previous steps. A third layer of filler should never be needed.
Once the second application of filler had been cut down with 80-grit and the DA sander, mo

Once the area is leveled to perfection, it’s a good idea to assure the shape of any bodyline. To do this, Leo marked the line with tape and sanded to it using 80-grit on a hand-powered soft block. He first taped one side of the bodyline and sanded, then moved the tape to the other side of the line and sanded from the opposite direction.
Once the area is leveled to perfection, it’s a good idea to assure the shape of any b

Hate that! You buy a car that looks solid, then a few months later rust bubbles appear. Take a grinder to 'em and--sure enough--there's a bigger problem than you thought.

That's what happened to our budget-built Duster. We initially took it to Car-Nation Auto Body hoping for a minor repair to the lower edges of the quarter panels. The guys at Car-Nation broke the news that: 1) The rust needed to be cut out to fix it; 2) By the time we repair that area, we might as well fix the door-dings in the quarters; and 3) If we have to match-paint the quarters, they're not going to look the same as the 30-year-old paint on the rest of the car. So, you guessed it--the Duster's getting painted.

But for now, have a look at how to fix mild quarter rot the easy way. The techniques shown aren't for hard-core rust-belt Swiss cheese or full-on show cars, but you can probably do them yourself if you have the right tools--in this story, "the right tools" means air tools, many of which may not be in the arsenal of the backyard dude. However, bodywork is very painstaking and much patience is required. In our experience, patience runs way thin when using hand tools, so the investment in a compressor and air tools is way worth it.

SOURCES
Car-Nation Auto Body 5450 W. Pico Blvd. Los Angeles CA 90019

Body Rot Repair

BODY SUPER-SECTION

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