How to Fix Hairline Cracks in Car Windows

Last Updated: October 26, 2022

Like windshields, car windows are highly susceptible to nicks, scratches, and hairline cracks. It can be tedious to repair a car window yourself, but it’s easy enough with the right gear and a few hours. Read on to learn everything you’ll need to do to get your windshield back into tiptop shape.

1

Check your windows.

Inspect all windows on your car including the back window and windshield. There may be additional cracks that require your attention.

2

Buy a bridge kit.

Bridge kits have everything you’d need to repair your windshield. Bridge kits have suction cups at each end of the bridge that latch onto the window and are the best option for hairline cracks on vertical car windows. These kits are available at various auto supply, hardware, or retail stores.

3

Clean the crack.

Get rid of any dirt, loose glass, or other debris. A metal probe works best for the cleaning process.^{[1]
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4

Add end cracks.

Use the metal probe to create bull's-eye cracks at each end of the hairline crack. Gently tap the metal probe so that the inner plastic layer of the glass is not damaged. This prevents further widening or spreading of the crack.^{[2]
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5

Put resin in the injector.

Follow the instructions to load-up the injector. Load the specified amount of resin into the injector as instructed on the bridge-kit packaging.

6

Put the apparatus over the crack.

Position the bridge apparatus so the injector is directly above the crack. Secure the suction cups in place. Add resin into the crack using the injector or use the pressure and vacuum controls of the injector to suck air out of the crack while forcing the resin in. When the crack has been filled with resin, remove the bridge from the window.^{[3]
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7

Wait for the resin to harden.

Let the windshield sit in the sun to harden and dry. Windshield repair kit resin does not air-dry; it requires UV light from the sun or an artificial UV lamp to adequately dry.^{[4]
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8

Apply resurfacing resin.

Use a generous amount of the second resin to maintain the repair. Use a cellophane patch, and cover the area that you just applied resurfacing resin to. Expose to direct sunlight or UV lamp, and allow the area to dry. After it is dry, remove the cellophane patch and gently scrape off the excess resurfacing resin with a razor blade to make it level with the surrounding glass to complete the car window hairline crack repair.^{[5]
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9

Clean the window.

Use a glass cleaner to clean up any remaining debris. Once the resin is dry, cleanup should be a breeze.

Community Q&A

Question

How do I fix an improper repair on a windshield crack?

Community Answer

If bigger than a quarter in diameter you're supposed to take it to a shop for replacement. I've tried the crack repair stuff before on longer cracks, and used some at each end to hopefully stop the spreading. It didn't last too long for me.
Question

My car windshield got a crack on my way to work by a truck loaded with sand and stones; the stone fell on my window and it cracked. How can I remove it (an easier and cheaper way)?

Community Answer

If it's bigger than a quarter, you have to get it replaced, because the "filler" stuff doesn't usually work, and it usually spreads too. If smaller in diameter than a quarter, there are some kits at auto parts stores, Amazon, even Walmart had one a while back. It takes a try or two to get it right if you've never done these before, but you can do it.

Warnings

If the crack on your window is longer than 3 inches (7.6 cm) then a windshield repair kit will likely not work for you. In this case, it is best to contact a professional.

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Professional resin injection methods usually provide better results than a do-it-yourself kit.

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