How to Fix a Leak Around a Car Rear Windshield

by Kate Evelyn

Having a leak around a car rear windshield can be very annoying. If you don't take care of it quickly, your car interior can get soaked during a torrential rainstorm. During a smaller storm, it can get just wet enough to leave a lovely mildew smell and get water spots on the upholstery. That makes it important to fix the leak when you first notice it, before it has a chance to get any worse.


Step 1

Locate the source of the leak. Ask a friend to pour a gallon of water on your rear windshield, moving the jug from left to right across the top, as you sit in the rear seat of the vehicle or in the hatch. As the water runs down the windshield, determine the spot where it starts coming inside the car. If the first gallon doesn't cause a leak, refill the jug and repeat as needed or use the garden hose.

Step 2

Take your screwdriver and gently pry the rubber window trim away from the windshield near the source of your leak, being careful not to bend or nick it. Check the channel (the metal well underneath the trim) for cracks or rust. Also inspect the bottom of the windshield's glass for nicks, chips or cracks.

Step 3

Wipe out the channel with a cotton rag dipped in rubbing alcohol so you have a smooth surface to work with. Sand off any rust with 80-grit sandpaper and wipe out any fragments. Fill the channel with polyurethane sealant using your caulking gun, leaving an eighth of an inch of space at the top of the channel to accommodate the trim. Before the caulk has a chance to dry, replace the trim you lifted up. Secure it in place with duct tape. The pressure on the caulk will help stick it back to the window, leaving it lying flat.

Step 4

Allow the caulk 30 minutes to dry, then remove the tape. Repeat the water test from Step 1 to ensure that you've taken care of the problem. If not, add more caulk and try again.

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