How to Repair a Car Window Crack or Chip

Car window glass is strong, but when you're driving at highway speeds, even a tiny stone can chip your windshield or shatter a side window. If your side window gets shattered, you'll have to replace it, but windshield chips, cracks, dings, and stars can sometimes be repaired without resorting to expensive windshield replacement. Follow these car window repair tips to ensure that the process goes smoothly.

Assess Damage Size

complex windshield damage — This windshield damage is too large and complex to be repaired. Little Hand Images / Getty Images

First, take a look at the size, shape, and complexity of the damage. Simple cracks and stars will be easy to repair, but complex cracks (e.g. branching cracks or cracks with multiple jags) may be impossible to repair.

Generally speaking, cracks longer than 3 inches and stars with diameters over 2 inches will be too difficult for an inexperienced DIYer to handle on their own. Experienced glass repair technicians, on the other hand, can easily handle stars up to 4 inches across and simple cracks up to 18 inches long. However, large cracks limit the strength of the glass – a good reason to consider windshield replacement rather than repair.

Check Repair Location

Large windshield cracks — Cracks on the inside of the glass can't be repaired. Don Klumpp / Getty Images

The location of the window damage plays a role in determining whether or not you will be able to repair it. If the damage is located in any of these places, do not attempt to repair it on your own. These situations require replacement.

The inside. If the window damage is on the inside rather than the outside of the car, the only way to repair the glass would be to flip your car upside down, because gravity doesn’t work that way.
The driver's view. If the damage is in the driver's view, do not attempt to repair it. Even a professional repair may cause distorted visibility. Driver safety is not worth any “savings” gained by avoiding windshield replacement.
Inaccessible or hard to see. If you can't see the damage, you can't repair the damage. If part of a crack disappears behind a molding, for example, it cannot be appropriately repaired, and the window should be replaced.

Keep It Clean

A long windshield crack. — If you wait too long, contamination and temperature touchstone may cause cracks to expand. Farmatin / Wikimedia Commons

Another consideration is the cleanliness of the break. If the break is fresh, cover it immediately with clear tape until you decide to repair or replace it. The clear tape will prevent foreign material from getting lodged in the crack.

If the crack is old, it may be too late to attempt a repair. Over time, dust, dirt, and water enter the crack, causing it to worsen. Daily temperature changes cause the glass to expand and contract, making the issue even worse.

Prevent Damage From Spreading

using a bridge to repair windshield damage — This car glass repair bridge precisely positions and holds the epoxy resin tube for a clean repair. BanksPhotos / Getty Images

There are a few different approaches to DIY car window repair. You can acquire a DIY kit for stars, pits, and small cracks, which should include most of the materials needed to complete the repair. However, you might also be able to get away with full-DIY solutions, sourcing your own parts. Here are the basic steps for any car window repair, no matter which approach you take:

Clear debris. If you’ve taped over the damage, remove the tape and use a pick to remove any loose glass. Use compressed air (the office equipment spray cans are a great portable choice) to clear dust and debris from the break.
Clean around the break. Use an alcohol pad to clean around the break. Do not clean the break itself. If alcohol accidentally gets into the crack, you may be able to use compressed air to dry it out.
De-stress. Use a 1/16-inch diamond-tip drill at the ends of the crack or at the center of the star to de-stress the damaged area. Drill only until you get through the first layer of glass. Use compressed air one last time to remove glass dust from the hole.
Bond. Most car glass repair kits include a “bridge,” which forces a syringe of epoxy against the glass and into the break. Follow the instructions in the kit. This usually includes a sealing ring and a locking syringe that can apply pressure and vacuum. Pressure forces the resin into the cracks, while vacuum pulls bubbles out of the resin. For DIYers, cyanoacrylate (also known as “super glue") may be good alternatives. Cyanoacrylate (not the gel-type) works well on cracks, while acrylic works well on stars.

Remember to prioritize your safety, and always replace a window if the damage has weakened or destabilized it. However, depending on the extent of the damage, you may be able to save yourself a few hundred dollars by fixing a broken car window yourself. DIY car glass repair kits cost around $25, and hiring a glass repair professional costs around $50.