So I have a 1991 accord and my back seat always getting wet and i cant seem to find the leak. Its not the tail lights or the trunk seal and I don't have a sunroof either I removed the drain plugs in the trunk so it's not pooling up and splashing forward when I drive. I have removed everything from the trunk and removed the back seat also found drain plugs under the back seat and removed them so the water that comes in will drain out plz help me out i think its the back window or something but idk anyone else have the same issue

 

Lay a hose on the roof and wait for it to trickle through. Easiest way to pin point it IMO. Make sure to blow all the water out and dry it up completely before attempting to fix/seal whatever it is.

-Amp

 

If a window has been replaced, it may have not been installed/sealed correctly. I would suggest removing the back seat and interior panels around the seat. Look for any dirt traces from water leaking in and any rust spots. The hose is the easiest way to see where water may be intruding. You may be surprised at where/how the water comes in. Check inside your rear wheel wells for any rust or holes.