CarbineElement

My 1986 mustang is having an interior water leaking issue where water enters from outside the car during rain and leaks inside from behind the dash and straight into the floorboard on both the passenger and driver side.

Has anyone had this happen to their cars and could help me in any way? The only way I can think to even identify where the leak is coming from is by leaning the entire dash forward, but I wanna see if somebody has any advice before I start that project.

I removed my carpet for this reason and I have to fix it before putting the rest of the interior back together and it’s very annoying. Any help at all is appreciated