Coolant question
 

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?

http://forums.pelicanparts.com/uploa...1656987712.jpg
http://forums.pelicanparts.com/uploa...1656987712.jpg

You should test the ph level in your coolant. They make color paper test strips

Try Evans coolant?
https://www.amazon.com/Coolant-EC53001-EC42001-Performance-Waterless-Gallon/dp/B014HC8HO2/ref=pd_lpo_2?pd_rd_i=B014HC8HO2&psc=1

For my old El Camino, I flush and replace the coolant every other spring. The radiator has virtually no corrosion visible, and the water pump lasts about 70,000 miles. It is free to replace for me since I bought a lifetime guarantee water pump 29 years ago.

I have a pressure coolant flush and refill setup.

As you well know, 6 month old coolant and a new sensor should not be looking like that. Is that sender a BMW branded sender, or some aftermarket one of the "wrong" material?

I drained and filled it about one and a half ago, when I replaced all of the coolant hoses, thermostat, water pump, etc. And then replaced coolant again in six months ago when I need some bottom in engine work.

In the old days, they have a kit that you tied into the heater hose and flushed the engine that way. Looking online, there are several brands of coolant flush. Obviously, I would want one awards with plastic and aluminum.