Directly under the body in the center, about 2 feet in from the rear, I noticed a small drip leak. There was a weak rubber plug that I yanked out and all of a sudden, about half a gallon of a water like substance poured out. Anyone know what this was? Update: it appears that the spare tire compartment was full of water. Any idea why or what could of caused this??? PC36100 ?
Likely to be water trapped in the spare wheel well, possibly leaking in through one of the rear light seals to the bodywork.
Take out spare wheel clean and dry the well leave rubber bung out till path of water ingress is found and rectified.
+1 The Gen II rear light assembly gasketing is, well... let's say usually functional, but on the scant side... thin, easily compressible strip foam gasketing, apparently off a roll and applied by hand... Did I say cheesy? When I had both assemblies removed, to replace '08 lights with '06 ones -- to get the black chrome brake light reflectors, I was suprised to see how different the actual paths of the gasketing was on the four assemblies. Lots of opportunities for leakage.
YES! Most probably it's a welding ... or a few! See here: http://priuschat.com/forums/gen-ii-...852-mildew-under-rear-passenger-carpet-3.html.
...this *might* help explain the hybrid battery water damage reported recently by an another owner (thread under Gen III Technical).