Loss of coolant - water pump?
My 2005 9-5 with 45k miles lost some coolant and I had to refill the expansion tank. Not much but still enough to cause concern. I noticed traces of orange coolant on the oil filter and oil pan. There isn't enough loss to notice coolant on the ground after it has been parked.
There sometimes is a faint burnt coolant smell when you open the hood. But not like when the coolant bypass valve was failing on a previous 9-5. And the traces of coolant near the oil pan and filter makes me believe it is not the CBV.
My first guess is the engine coolant pump. Or could it be something else? It is difficult to see in that area so I am not sure how to check.