Here, we have a 1979 Firebird front ground effect that has a four-inch crack and a broken tab.
These older Firebird parts are made of polyurethane plastic.
So for this repair, we will be using Polyvance's airless plastic welder and urethane welding rod.
Other repair products, such as two-part adhesives, don't adhere to polyurethane plastic very well.
However, when using urethane welding rod as an adhesive, you can get a strong, permanent repair.
In this video, we will show you how to repair small cracks and tabs in polyurethane parts
using Polyvance's Model 7 airless plastic welder and R01 urethane welding rod.
As with any repair, you want to start out by thoroughly cleaning the part to remove any dirt or grime.
Next, align the crack and use aluminum tape to hold the crack together.
On the back side, v-groove about halfway deep into the plastic,
making sure the v-groove is centered along the crack.
If the crack extends to the edge of the part, make sure to v-groove along the edge,
about two inches on each side of the crack.
This edge v-groove provides extra reinforcement for the repair.
If repairing a tab, v-groove about an inch around the crack.
To weld polyurethane plastic, you will need to set your airless plastic welder to the PUR setting.
Begin welding by feeding the rod through the tip of the airless welder,
holding the tip slightly above the surface to avoid burning the base material.
Move slowly so that the v-groove is completely filled with welding rod before moving on.
Finish the weld by doing the edge v-groove last.
Weld a broken tab the same way; move the welder slowly to fill the v-groove completely.
Smooth out the welds if necessary.
After the plastic is completely cooled down to room temperature,
remove the aluminum tape from the front side.
Use plastic cleaner to remove any adhesive residue left behind from the tape.
Next, make a deep v-groove halfway into the plastic,
making sure to expose your existing weld on the back side.
There is no need to make an edge v-groove on the front.
After v-grooving, weld the front side.
Remember to hold the welder tip slightly above the surface, making sure not to burn the base material.
Once the welds are complete, allow the plastic to cool to room temperature.
Once the plastic is cool, grind the front welds using 36 grit to 50 grit on a Roloc disc.
Next, sand the repair area using 80 grit sandpaper.
Sand at least four to six inches around the welds.
Here, we are refinishing the whole part, so we sanded the paint completely off.
If repairing a tab, now is the time to drill the tab hole out.
Blow the part off with air and use plastic cleaner to remove any dust.
Next, apply filler to cover the welds and any other imperfections.
Here, we're using Polyvance's 2000-T Flex Filler 2 epoxy.
Once the filler has cured, sand and block with 80 grit sandpaper and finish out with 180 grit sandpaper.
Now the part is ready for primer.
Here, we used Polyvance's 3043 All Seasons Black Jack waterborne primer.
You may need to block and prime multiple times to achieve desired appearance.
Polyurethane parts are often thought of as unrepairable.
However, these parts can be repaired and restored to like-new condition
by using products and techniques from Polyvance.
Thanks for watching!
Let us know in the comments what you thought of this repair,
and check out our other videos for more plastic repair tutorials.