Why Does the Windshield Crack by Itself?
2 Answers
Here are the specific reasons why windshields crack by themselves: 1. Heating and cooling during the laminated glass manufacturing process: Windshield cracks usually occur at the edges of the glass, primarily due to the heating and cooling process during laminated glass manufacturing. This process creates internal tensile stress and surface compressive stress in the glass. The glass remains stable when these forces are in balance, but if not, it may crack spontaneously. 2. Exposure to cold water after being in the sun: If car glass is exposed to cold water after being in the sun, the extreme temperature change may also cause the glass to crack. 3. Recommended actions: If the windshield cracks by itself, pull over immediately and do not continue driving. For safety reasons, it is recommended to replace the windshield directly.
Last time I drove back to my hometown, my car was exposed to the scorching sun, and I immediately turned on the air conditioner blowing directly at the windshield. Suddenly, a palm-sized crack appeared. The mechanic later explained it was due to thermal stress—the glass couldn’t handle a temperature difference exceeding 50°C. Another time, a small chip from a pebble on the highway went unnoticed, but on a bumpy road, it suddenly spread into a spiderweb crack. An experienced driver told me that if the rubber seals around the glass edges age and let water in, freezing in winter can expand and crack the glass. The scariest was when improper window tinting caused uneven heating—my colleague had to replace his windshield because of that. Bottom line: avoid pouring hot water or blasting cold air directly on the glass, fix minor damage promptly, and now I always check the edge seals during car washes.
