Hey
so decided to change my oil in my manual transmission (98 x3). took the wheel off and opened the drain plug....nothing comes out

uzzled:
open the filler hole and about 500ml of fluid drains from the filler plug...nothign else...
how do i get the rest out....i take it the drain plug is blocked? any ideas and one experienced this before? heard of this before?
asap help apreciated...as car is outa action