What causes water to leak into the interior every time it rains heavy in a 1993 2 door Sunbird?

Answer 1

your seals could be dry rotted or they came loose some where around the windshield. does it have a sunroof? No sunroof. What about firewall rust? Common problem with sunbirds/calaliers, due to poor door seals, I had both a sunbird that did that all the time as well as a buddies cavalier that did it. Remove the wipers, remove the cowl screen directly under the wipers, and check each corner. Bet you they are rotted. Wait until your interior light comes on when you close your door and go out when you open them! Try and seal up the corners way under the windsheild. Absolutely! These cars were very leaky for water. Trunk, doors, door seals, window seals, tailights, you name it. My suggestion is, get someone to sit inside the car (with all carpets pulled up) and turn a hose on it, heavy, then look for leaks. There is some really cool kind of glowing stuff you can use with a blacklight or UV light or something and it allows you to trace where water leaks are in cars and such. Real CSI kinda stuff. Don't know what it's called but try Googling it for Glow and Leaks and you should find something. The hose on a nice bright sunny day though is how I found mine. When you find the leaks, caulk the heck out of them!