Water oil pollution

Greetings from Guatemala I have in repair a Subaru Justy 1994 Motor 1000cc 3 cylinders. I contaminate the water with lifting oil the cylinder head thinking about the packaging of it but finds no problem in the packaging. It has an engine front cover where the water and oil pump is. Ask there is the possibility that water with oil is contaminated by that place.

Hello, look if you have an oil or refrigerador intervener this goes in the oil filter if it carries it, bridge the 2 sleeves and test