After installing the water temperature gauge a few days ago, I pulled out the sending unit today to do some work on the housing. I was surprised that the new brass sending unit had some green funk on it. I use BMW approved coolant which is blue in color, end it was replaced within the last six months.
What would cause this and what’s the best way to do a coolant flush?
Edit: is the coolant reacting to the brass through the small current at the sender?
