When mine stopped working it would also leak out immediatley after filling also. My issue was a hose had pulled off a nipple on the bottom of the tank. The tank is easy to get to. About 6 phillips head screws and one 10mm bolt I think is what I had to take out to allow the front driver wheel well plastic to pull back far enough to get in there and inspect/plug hose back up. After that it held fluid and worked fine. Mine has never been in a crash though. Hopefully you dont have a crack in it, or if you do maybe you can seal it up with some epoxy.

Also the little lines that come out of the driver side under the hood and run up the underside of the hood are known to dryrot and crack from all the heat cycles and age. Another easy fix if so.

 

I will get under the car and check her out soon. Thanks for the insight.