Leaky windshields tend to occur mostly in older vehicles, but sometimes leaks happen even in a newer car. A leaking windshield is usually caused by defective window sealant, as a result of poor windshield installation or simply old age. Depending on the size of the leaking area, you can usually fix an annoying windshield leak yourself, without spending much money. If your entire window severely leaks around the edges, you may need to take your car to a shop specialising in windshield repair.
Closely inspect the inside of the windshield to locate the source of the leak. While someone sits in the front seat of the vehicle, spray water over the outside of the windshield, using a garden hose. Double check all areas of the window and closely look for water seepage on the inside of the glass.
Mark the leaking areas of the windshield using a piece of tape, if more than one leak exists. Place tape on the inside of the glass, not the outside. Spend at least five minutes closely inspecting the glass for leaks, placing tape where necessary.
Head down to your local auto parts store and purchase a tube of silicone windshield sealant. Purchase either an individual tube of sealant, or a kit, which might include a handy tool for applying the sealant.
Remove any dirt or residue from the section of the windshield where you are going to apply the new silicone sealant. Remove old leaking sealant using a razor blade. Use a rag to wipe any dirt off of the glass.
Remove the tape from one of the leaking areas and begin applying the sealant. Insert the nose of the sealant tube into the leaking crack, and slowly squeeze sealant from the tube. Squeeze out only small amounts of sealant at a time, to avoid heavy build-up of sealant on the dashboard or glass.
Allow the silicone sealant to completely dry, according to the specifications on the tube, before testing the leak.
Test the dry sealant using a bucket of water or a garden hose. Apply water to the windshield and inspect the inside portion of the glass. If leaking persists, use a professional repair service to remedy the problem.
For major windshield leaks, take your vehicle to a professional glass repair service.
Do not test the leak, or drive in the rain, without allowing the silicone sealant to completely dry.