I was changing out my battery and noticed a puddle of water on the battery tray. Removed the tray and noticed all the harnesses under the tray are wet. I was having some grounding issues and this may be the culprit.
I've removed the plastic piece attached to the windshield and noticed the seal is all mushy and there was a break (see pictures). Replaced the whole seal with a thick layer of butyl tape temporarily. After I reassembled everything back, I hosed down the windshield but noticed it is still leaking. Not sure if the seal I'm using is just not effective or if this water flow is by design. Anyone know where I can purchase the same seal used in the plastic piece.

 

Either buy a new piece or go to the junkyard.

 

looks like this is by design (according to users over at the g35 forums), if anyone is washing their car, can you check your battery compartment for water. especially the battery tray.