Abstract: Method and apparatus are disclosed for separting a refrigerant from oil and/or impurities contained in components of a compressor cooling system. When retrofitting a compressor cooling system using a CFC refrigerant into use of a chloride HFC refrigerant, the mineral oil mixed into the CFC refrigerant has to be seperated. It is thereby a problem that the oil is spread in all the components of the system and that existing cleansing technique is not efficient, since it does not cleanse all the components as the technique used involves that some of the components are by-passed. According to the invention these problems are solved by temporarily connecting an oil removal device in series with the compressor cooling system without having to by-pass any components. The compressor cooling system is filled with refrigerant, e.g. R134a.