Symptoms
- Crack visibly longer than when first noticed
- Crack may branch or split into multiple lines
- May worsen quickly with temperature swings or bumps
- Visibility may become affected if it crosses the driver's view
Likely causes
- CommonExisting chip or crack under stressOnce glass is compromised, vibration, temperature change, and flexing of the body can extend the crack.
- CommonTemperature extremes (hot defrost on cold glass, etc.)Sudden temperature changes stress the glass exactly where it's already weakened.
- PossibleContinued driving on rough roadsVibration and flexing of the body can gradually extend a crack over time.
- Less commonNew impact near the existing damageA fresh rock strike near an old crack can cause it to jump in length suddenly.
What to do
- Avoid extreme temperature changes on the glass; use gradual defrosting rather than full blast on a very cold windshield.
- Avoid slamming doors or the trunk, since the pressure change can sometimes stress an already-cracked windshield.
- Get an assessment from an auto glass shop as soon as possible; length and location determine whether repair is still possible.
- If the crack is in the driver's direct line of sight or longer than about a foot, plan on replacement rather than repair.
- Check your insurance policy for windshield coverage, since replacement costs can be partly or fully covered depending on your plan.
- Have the windshield replaced by a reputable shop, and avoid car washes or highway driving for the time recommended afterward while the adhesive cures.
Tools and parts
Windshield replacementSearch: “windshield replacement for [year make model]”
When to call a pro
See an auto glass shop promptly; on many newer cars, replacement also requires recalibrating a windshield-mounted camera for safety systems, which needs proper equipment.
Safety
Use caution
A crack that impairs the driver's forward visibility, or one that's grown significantly, is a safety issue; get it repaired or replaced before continuing regular driving.