Plastic is a common trim material in vehicle interiors and exteriors. It’s affordable and looks great when it’s brand new, giving the vehicle a sleek black accent to its look. Unfortunately, plastic trim tends to grow brittle and its color fades after a few years of sun exposure. If you own a vehicle with plastic trim, you might have experienced this brittleness firsthand. Maybe a piece of your vehicle’s plastic trim suddenly broke off unexpectedly, or an accidental kick formed a crack. Whatever the case, while replacing the entire piece of trim is possible, you might also want to consider repairing the old piece instead. In that case, here are some tips and tricks for plastic trim repair.
First things first, you’ll need to examine the repair area. A crack in the trim might go farther than you think. Patching only a section of the crack will only lead to the crack growing again over time, sometimes even over the course of the repair. In addition, if the plastic trim piece has snapped in two, see if the pieces fit together or if there are missing bits. Position everything together the right way before epoxying or welding.
As an additional step, you might want to identify the type of plastic you’re dealing with as well. Some plastics need special treatment before you can paint or use epoxy on them. Your car interior’s plastic trim repair might need a very different process compared to your car door’s plastic trim repair.
The type of prep you need depends on whether you’re planning to fuse the plastic trim with epoxy or weld it with a plastic welding tool. Either way, you’ll want to clean the area first. You can use wax and grease remover, window cleaner, soapy water, or plastic solvent. Some cleaning supplies might suit different plastic types better than others. Don’t forget to sand off any paint and rough edges in the area as well. For larger gaps, cut a v-shaped groove between the piece to give the filler or epoxy more surface to hold onto.
If you’re using epoxy to fill the crack or to fuse the broken pieces together, roughly sand down the plastic to give the epoxy a better surface to cling to. Consider drilling holes on either end of the crack to give the epoxy a better hold on the plastic after it dries.
The first method for fixing broken plastic trim is to use epoxy, which is a viscous polymer or prepolymer that cures and hardens over time when mixed with a hardener or curing agent.
The epoxy typically comes in a two-part pack, one containing the polymer or prepolymer and the other containing the hardener or curing agent. Mix the two according to the directions on the packaging to activate the epoxy, and use the resulting mixture to fill in the gap in the trim. Make sure to follow the directions for mixing the epoxy. If you don’t get the mixture right, the epoxy might not hold.
Some epoxies harden in as fast as five minutes so work carefully but quickly. Depending on the epoxy, it might take longer to fully cure. Make sure to mix the epoxy parts together thoroughly so it hardens properly. For larger cracks, use mesh tape across the crack to make a sort of backing for the epoxy, and apply the epoxy in layers rather than in one large glob.
The second plastic trim repair method is plastic welding. For this, you’ll need a specialized plastic welder and, if the gap in the trim is very large, a plastic filler rod that uses the same plastic as the original trim. The idea is to melt the plastic back together using copious amounts of heat, delivered through the metal end of the plastic welder. This closes the crack by forcing the plastic to fuse to itself. If the gap is large and you don’t have a matching plastic filler rod, you might need to cut a bit of plastic from a less conspicuous part of the trim and weld that into the gap. Use the extra plastic as a filler.
Once you’ve patched up the plastic trim, you’ll likely find that it looks a little rough or untextured. That’s where sanding and painting come in. Patching up plastic trim won’t give you perfect results right after the patch. You need to add a little more effort into making the repaired area match the rest of the trim.
Before you start sanding, spray down the plastic with a white guide coat to easily spot any damage. You can do this to the whole piece of plastic or just the repair area depending on how much of the trim you want to paint. Sand down the area you want to paint with 320 grit sandpaper and clean it again with wax and grease remover. Use two coats of spray-on adhesion promoter to soften the plastic and help the new paint stick. Then, pick a textured automotive aerosol paint like a truck bed liner or a light grain paint for the final 8 to 15 layers.
Make sure to pick a paint that matches the rest of the trim in your vehicle. When picking the paint, check the trim in multiple places around your vehicle and on both of its sides. Sometimes the trim on one side is more faded than the trim on the other side. You can add another colored layer on top if you want a non-black trim.
When picking paint, check if it matches with the rest of the trim in your vehicle. Sometimes the trim on the other side is more faded than the other.
–Anthony Harlin, ASE Certified Master Automobile Technician
If your plastic trim is entirely crack-free and you’re only looking to restore its color, consider using a heat gun or torch to draw out the oils and return the trim to its original shiny state. This will damage the plastic though, so as an alternative you might want to use trim dressings or restorers. Painting over the entire piece of trim as we outlined earlier is also a good option.
Whether you’re looking to repair a hard-to-find vintage trim piece or simply saving some money on a costly replacement piece, knowing how to repair automotive plastic trim can be very handy. We hope this guide’s helped you understand the process better.
Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.