When the seal surrounding your windshield is faulty or damaged, it will begin to leak. The leak will not be noticed from the outside of the vehicle. You will see it from the inside, as a drop of water from the top or a little puddle on your dash after a good rain or after you wash the vehicle. If the leak is small, you can fix it yourself, but if the leak is bad or does not stop after following these steps, you will need a professional's help.
Wash your vehicle or wait for it to rain to locate the exact spot in the seal that is leaking. Find the drip on the inside of the windshield.
Dry the windshield, both inside and out, using a clean, dry towel or soft cloth. Do this to remove all water which will interfere with the adhesive adhering to the glass properly on the inside and to prevent any more water from coming in through the leaking spot from the outside. Put a small, 1/4-inch-long piece of masking tape where the leak is, centring the centre of the tape with the exact spot the drips are coming from.
Locate the tape that identifies the leaking spot. Get a tube of windshield adhesive ready by cutting off the end tip of the tube, 1/4 inch from the tip, using a utility knife. Cut the tip off at an angle for easiest application. Remove the tape from the windshield where the leak is. Hold the tip of the tube exactly where the tape was and squeeze the tube, allowing a 2-inch-long bead of adhesive to run along the seal in the seam where the windshield and seal come together.
Use the tip of your index finger to smooth over the adhesive. Wipe off any excess adhesive from your finger onto an old cloth or grease rag. Use your finger to push the adhesive into the seam, which will ensure that it bonds with the windshield itself, and with the seal around the windshield where it is leaking.
Allow the windshield adhesive to dry overnight before touching it. Remove excess adhesive, using a utility knife with a straight blade. Check to see if the leaking spot of the windshield's seal has been repaired by washing your vehicle, spraying the windshield completely and looking inside of the vehicle in the spot where the leak was. Apply another layer of adhesive following the same steps if the windshield is still leaking. Take your vehicle to an auto-glass repair shop if the leak persists, as you may need to have your windshield resealed.
Use a flashlight to help you see the leaking spot better.
Wash hands promptly after using adhesive.