2001 BMW 325i Q&A
2001 BMW 325i Question: AC not holding freon. Could it be the O Rings?
Yes, along with any other point in the system that holds refrigerant. It will be cheapest in the long run to have the system tested for leaks. If you charged it with a refrigerant with dye, you may be able to find the leak point with a UV light. - United Auto Service Center