Rust Repair II
by Pat Goss
We’ve finished our metal patch on the door of our Cadillac; now it’s time to do the finish work.
Which means it’s time to make mud pies! Or, more precisely, we’ll use plastic body filler, which you may call bondo, to level our patch with the rest of the surface of the door. But don’t make the mistake many do-it-yourselfers do and mix your filler on raw untreated corrugated cardboard. In some cases the cardboard will absorb some of the resins from the filler, leaving you with filler that improperly cures-or worse, it blisters after it’s been painted. That one will really kill the mood!
Use a clean sheet of metal or like I’m doing smooth plastic. Use a regular body shop plastic spreader to apply the filler to the car trying to maintain the appropriate curves. After the filler hardens you can use a couple of different tools to begin forming the shape. One is referred to as a cheese grater, or you could use a body file like this Eastwood tool. Use the tool to shape the filler and establish the proper curve to match the rest of the panel. And once you have the basic shape established you will most likely find that you need to apply another coat of filler.
Then it’s time for sanding. Now, here, I prefer a sanding block for large panels, like our door, because it won’t fall into the low spots causing dimples and waves. This is an orbital sander, which does have a purpose in a job like this, but it’s primarily for shaping, it’s not for finish work, because when you get down to the real finish work, if you’re not careful with this, you’ll wind up with a lot of waves and ripples in the surface. Now, if the panel has multiple contours, you’ll have to use your artistic ability and feel to make the repair match the rest of the panel. You may have to use multiple coats of body filler to build the surface to the proper contour. And one thing that helps in this process is what we call a guide coat, which is nothing more than dusting the surface of the repair with black spray paint.
Once the paint dries you re-sand the surface and any black paint that remains indicates a low spot which must be refilled. But you may also find high spots in your patch and for that you use a body hammer and dolly to lower the surface of the metal. These steps are repeated until you have reached the proper contour and a smooth, wave- and dimple-free surface. And that’s just the beginning; you still have a lot more work to do to make the repair ready for paint.
If you have a question or comment, write to me.
The address is MotorWeek, Owings Mills, MD, 21117.