well when oil gets into water it turns into a cream, and it can be the head gakest with apin hole in it as i know worked on a car with, but if it has a car can get years before anything happens coz it dont show up inless u test it,
well it cold be the head gasket has a pin hole init so over time bits of oil can get in the coolent, but if it is it well take so time to become anything bigger so should be ok but i would flush the radiator and pipes though. one question has the head gasket been changed before do u know ?
its easy to do it ur self or if u get a garage it would be about 200, i wouldnt pay anymore an that realy in less u love the car lol i wouldnt get one off ebay inless its a shop coz wot people do is clean old ones up and sell them