Tech Article: Dash Cracks
by Marc Sayer
Many of us think that early series Z cars came from the factory with a cracked dash. Cracks are a major problem. If you are doing a restoration, replacing the dash is the way to go. But it is expensive and you spend days removing the old and installing the new. Another option is to install a dash cover. Dash covers do not look that good, and wind up to be over a $125 investment themselves.
Dash cracks can be repaired. The method I use is not perfect in that you can see where the repair was made. But if you take your time and be very careful, the repaired crack will be very difficult to see. The work can be done without removing the dash from the car.
You will need the following:
- Masking tape
- Razor blades
- Rubber Gloves
- Fiberglass resin
- Steel wool
- Sand paper- 24 grit, 60 grit, 150 grit, and 220 grit
- Black paint to match the dash (matte black or universal black are close enough)
- "Great Stuff" brand foam sealant
1). With razor blade in hand, open the crack to 4" wide
2). Use the masking tape to protect the plastic around the crack. This keeps you from having to sand the sealant off the plastic. Sanding will remove the texture lines from the dash around the crack.
3). Spray "Great Stuff" into the crack and let harden. Great Stuff is a spray that hardens to a texture like Styrofoam. It expands as it hardens. Donít let it bother you. Use the razor to cut off the excess after it dries. It is extremely sticky and will adhere to anything. The directions say to wear rubber gloves because it will not come off your hands. Believe them!! Nothing dissolves it and it is so strong it will tear your skin off. On the positive side. This stickiness means your repaired crack will not reopen.
4). Use the 60 grit, 150 grit and 220 grit sandpaper to smooth the foam into the crack. Sand the foam until it is slightly below the plastic surface. You will use the fiberglass resin to fill back to a level surface.
5). Remove your masking tape and retape. During sanding, you have damaged it to the point it will not protect the plastic from the fiberglass resin.
6). Use the fiberglass resin to coat and seal the Great Stuff. The resin will soak in some. Use several light coats rather than one big one. You want to minimize your sanding, so as to not damage the plastic around the crack.
7). When you have the resin even with the plastic, remove the tape and touch sand to insure a smooth surface between the resin and the plastic. Now you are ready for the most difficult step.
8). The fiberglass resin surface needs a texture to match the texture of the original dash. This is done by pressing the 24 grit sandpaper into the resin just before it is completely dry. "Paint" a thin layer of resin over the repaired resin with a paint brush. At the same time, paint a few practice strips on a piece of cardboard. As the resin hardens, use the practice strips to test when the resin is the right hardness. The resin should be hard enough to pick up the texture of the sandpaper. It may take up to a dozen Ďtest stripsí to find just the right timing, press the sandpaper into the resin on the dash.
9) After the resin is completely hard, use steel wool to remove the harsh corners to blend into the texture of your dash.
As stated earlier, itís not a perfect repair. But it will take 30 minutes a day for 3 to 4 days and cost about 10 bucks. Thatís 1/10th of what a dash cover takes in time and money and 1/50th of what a new dash takes.