Plane mad Harry

Hi, I've got a 2002 Impreza WRX and want to know if the iacv has water from the cooling system running around it, because I want to take it off and clean it but when I loosen the screws a trickle of water comes out, if it has got water running through it how difficult is it to bleed the water system afterwards, I've worked on other motors I've owned but was wondering if the cooling system on a Subaru was different.
Thanks In advance.