How To Fix a Cracked Bumper
That’ll buff right out, after you follow these steps.
Time Needed: 2-3 days, Difficulty: Medium to difficult, Cost: $50-$250, depending on the tools you have
It’s nearly impossible to drive for any extended period of time without something damaging your car. Maybe you accidentally misjudged a turn and hit a parking pole, or maybe you were the victim of a minor fender bender. No matter how it happened, the result is the same. Your ride is messed up, and you need to fix it.
Once you get over the distress of an accident, you’ll want to get your cracked bumper fixed sooner than later. On top of being an eyesore, the crack could spread during driving, and pieces could break off. Not only that, but if the crack is on the front bumper, your gas mileage could even decrease, similar to the way it does when you have a damaged undertray.
Not to worry, though, this step-by-step guide will help you fix your cracked bumper before the weekend is over.
The Safety Brief
Safety comes first. We want you to get this job done in one piece. This job requires some grinding, sanding, spray painting, and mixing epoxy. To ensure your skin remains unblemished and intact, you’ll want to make sure you wear gloves, safety goggles and EHS/PPE rated dust masks. On top of that, you’ll want to work in a well-ventilated area. Lastly, make sure to check the laws in your state regarding the disposal of harmful chemicals before throwing anything away.
The Tools & Parts You Need
Don’t get stuck in the middle of a job without the parts you need. Gather everything required for the job before you start.
- Rotary tool with grinding bit
- Sandpaper: 80, 180, 320, 400, 600 grit. As well as 1500, 2000, 3000 and 5000 grit (for wet sanding)
- Sanding block
- Microfiber towels
- The car’s paint color in a spray can
- Acetone or alcohol
- Locking pliers
- Automotive masking tape
- Drywall mesh tape
- J-B Weld plastic bonder
- Plastic pan or non-absorbent mixing board to mix epoxy
- The car’s paint color in a spray can
- Automotive primer
- Automotive clear coat
- Disposable gloves
- Safety goggles
- Respirator mask
- Spray bottle with soapy water
The Task: How To Fix a Cracked Bumper
If you follow these steps, your bumper should be in good shape.
1. Remove the bumper.
Clean the area of the crack with soap and water thoroughly. Follow this by also using wax and grease remover. Make sure to get the edges of the crack. Dry thoroughly.
2. Grab your rotary tool and grinding bit.
Working specifically on the inside, unpainted portion of the bumper, begin to grind a v-shaped groove into the edges of both sides of the crack. Take your time with this.
3. Thoroughly sand the area of the crack on the inside.
Sand the area in as many different directions as possible. Follow though about two inches outside of the crack. The rougher the area, the better the epoxy will hold.
4. Use your locking pliers at the end of the crack.
You may need another person to help you do this. Follow this up by using tape on the painted side of the bumper to hold it all together as perfect as possible.
5. Grab your J-B Weld plastic welder.
Follow the given instructions to mix the compounds together. Use a plastic tray, or non-absorbent mixing board for this. Apply the epoxy into the crack smoothly. Make sure to fill the crack a little more than flush.
6. Use mesh to bolster the area.
Place some drywall mesh tape on the unpainted side of the bumper, on top of the epoxy, to help secure the crack even more. Apply more epoxy on top of the drywall tape. Allow to dry for at least 12 hours.
7. Confirm that the epoxy is dry.
Then remove both the locking pliers and masking tape (on the painted side).
8. Rough the edges.
Use the 320 grit sandpaper to rough up the edges of the crack on the painted side. The scratches and slight grooves will help the welding bond together. Use acetone to clean the area thoroughly and allow it to dry. Once dried, follow the instructions once again for the J-B Weld plastic welder, apply to crack and spread about a 1/2 inch out, on each side. Allow to dry per instructions.
9. Sand the body filler.
Start with 80 grit sandpaper on the area with the body filler until flush with the rest of the bumper. Clean the area with water and acetone. Follow this process, going from 80 to 180, 320, 400 and lastly 600. Finishing by wiping clean with water and acetone.
10. Now it’s time for a primer.
Begin by taking your piece of paper, and curving it on top of itself without bending. Tape the paper to the paint, with the curved end of the paper placed about 0.5 inches outside of the area you’ve been working on. This is to help feather the primer and avoid hard lines. Get your primer ready and begin spraying a light base layer in back and forth motions. Avoid staying in one spot for too long. It’s always a good idea to follow the instructions on the paint can. Once dried, you may need to apply a second layer. If so, make sure to keep the coat very light. Allow to dry again. Remove the paper masking.
11. Wrap your sanding block in the sandpaper.
Begin sanding outward into the good paint. Avoid spreading too far out—two inches is just fine. Avoid pressing too hard while sanding. You want to allow the sandpaper to do the work. Finish by cleaning the entire area thoroughly.
12. Grab a ruler and pencil.
Mark a dot about 1/4 inch from the end of the crack. Drill a small 1/8-inch hole at the marker through the bumper. This is optional according to some, but this process relieves tension and prevents spreading, so that you won’t have to do the entire job over again. Don’t worry—it’s not noticeable until you’re up close.
13. You’re on the home stretch and ready for spray paint.
Use the previous curved paper technique to mask the area. Read the instructions on your paint can, and begin applying to the area. You want to apply light, even coats to avoid paint running. Once dried, it should look matte. Which means you’re ready for your next coat. You’ll want to follow the painting procedure three times.
14. Time for a clear coat.
To avoid orange peeling, you’ll want to do this handy trick. Take your clear coat can, and submerge it in the hottest water you can get from your sink for a few minutes. This gives you a better spray pattern. Dry the can, and begin spraying. You’ll want a relatively light coat, but full coverage. Allow to dry. Do this three times, with the final coat being *slightly* thicker while still avoiding paint run. Allow to cure via the instructions on your can. Remove the masking paper. Depending on the size of the crack and how thorough you want to be, your job can end here. But if you want the bumper looking as perfect as possible, continue with the final steps.
15. Grab your sponge, spray bottle with water, and 1500 grit sandpaper.
Wrap the sponge in the sandpaper. The sponge helps to even out the pressure applied when sanding and helps form with the curves of the car. Spray down the sandpaper, and the entire area as much as you can. Begin sanding by using long, up and down motions, while moving along the entire area. You’ll want to go a little into the old clear coat. Don’t stay in one area for too long. Once finished, clean and dry the area. The area should start to look a bit hazy. Follow the same procedure going from 1500 grit to 2000, then 3000 and 4000.
16. Reinstall your bumper.
Finish the job by polishing the entire area. This will make your bumper look as close to normal as possible.
You did it! That was some tough work. Don’t forget to brag to your friends about how you did this all by yourself.
FAQs About Fixing a Cracked Bumper
We can’t read your mind, but we want to try to answer any questions you have before you start the job. We’ve selected common points of confusion from our experience, as well as commonly asked questions from popular search results. We answered those questions below.
Q: Are there alternative methods to fixing a cracked bumper?
A: This is just one of many methods. You may have heard of the zip tie method in the drifting community, which is a quick and fast approach to get the car back on the road as fast as possible. Some methods take longer, cost more, or look less pretty.
Q: How long will this fix last?
A: If completed correctly and carefully, this should fix your bumper for years to come. Naturally, though, you should avoid any collisions or love taps with your garage door to keep the bumper intact. Also keep in mind that other factors like extreme weather could affect the crack.
Q: Should I just replace my cracked bumper instead?
A: That’s always an option, but it could cost you significantly more. Most replacement bumpers come unpainted, which increases the cost.
Learn More From This Helpful Video Tutorial
Car Bibles editors understand that not everyone is a text-based learner. For those kinesthetic people out there, we have your back with a video showing you exactly how to fix your cracked bumper. We pulled it from one of our favorite, most trusted sources and it’s a great additional resource. This video uses the same process as the one in this tutorial, with a few steps missing. We recommend using it more as a visual aide to complement our guide.
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