What is this bolt?

I have 08 std which did the same thing the dealer tried cleaning out the thread, put in a copper washer and retentioning it, it still leaked the dealer then contacted the Aussie distributor and on their advice removed and bolt cleaned it and applied a sealant, after a while and it has not leaked but the distributor said they would replace the lower engine case which is what the bolt is holding to the upper case there was a suggestion that it may be poreus, only time will tell. the sealant idea was to elimilnate any chance that it was leaking throught the tread