Kestas,

Thanks a lot for your opinion. I'm not sure about calcium deposits. I don't see anything strange in the radiator but since it's been runing on tap water for too many years I just suposed there must be some calcium. Water in the system looked 100% clean before the oil contamination. How can you tell if there is calcium or not? By looking inside the hoses or something like that? All I see inside the hoses and fittings is oil contamination. BTW, our local tap water is potable and soft with neutral PH.

I think I'll remove the termostat and do a flush with comon detergent first and if everything looks clean after that, I'll put some new coolant and leeve it like that.

BTW, the part that caused the oil contamination is called the intercooler or does it have a different name?

Thanks again,

Juan