[BMWfan73]

New to me 2015 35i, 69K miles. I'm the second owner and the car is immaculate. However, with the notorious water pump failures, I have been checking on things in preparation for when it's my time. To my knowledge, the pump and/or t-stat have never been changed on the car. I don't know for certain because I purchased the car from a non-BMW dealership and the carfax service records were thin, basically nothing noted past the original warranty services. I decided to check out the coolant tonight and test it since I don't know if it's ever been changed or not. Now, my understanding is that the BMW coolant is blue, but when I used my tester it is a very light green, almost clear with a tinge of green/yellow color. Looks like extremely watered down mountain dew or gatorade. See photos. Any ideas? Should I just keep running with it until the pump goes and then have it flushed and refilled with the blue BMW or flush it now and start over?

[pungo]

Green coolant was probably used to top off the blue coolant, or after a repair, very common for an all purpose shop to add green universal coolant. Since there are 4 balls floating, you have freeze protection. Who knows when the pump may go, I've seen many N55 with 100k+ miles on the original pump. If it were mine, I'd flush it now since you don't know what they put in it and fill with BMW coolant, it's not expensive.

[Opie55]

I agree with pungo - I'd flush it. I have my doubts that was even BMW blue topped off with universal green. It does not seem to have retained any blue color at all, yet it's a very weak green so it's not all universal coolant. It almost looks like Xerex, which is the approved Mercedes coolant replacement and has a very light yellow color.