2005 Ford Freestar coolant leak

Sorry I am french so I will try to explain the best that I can. I buy a 2005 ford freestar with a 4.2 on it. He lost some coolant just when is hot and just a little so I check it and it look like it came from the front passager side, near the crankpully. So maybe the waterpump but non, she is ok. So I cannot really see but it look like comming from the place where we put the oil filter (or up) do it's possible?Do there is some coolant on this place? Is it a oil cooler? Do the engine imself can be broke crack or something even if it run well?And if not what it can be? Thanks before