i changed my water pump like, two months ago. :P
so unless the installation was wrong and the water pump gasket is leaking... (pero in my experience when the water pump was leaking, ANG BILIS mawalan ng tubig, as in one day lang)

i've found a small leak (at least i think it is..) on my IAC valve. this is probably what's causing the erratic idle.. will try to change the hoses.