pjc

Thanks, billford, very helpful. Reading those procedures, it certainly seems the two coolant systems are independent. I'll report back after I do the work in a week or two.

New member here. Greatly appreciate the help provided by forums like this. I'm preparing to do a coolant change on my daughter's 2012 Fusion Hybrid. As far as she knows it's never been done before. She's not the original owner, but she has owned it since before 100K miles, which is the recommended change point. We're now at 128K. The coolant is not exactly dirty and has no signs of oil contamination, but it's cloudy enough to confirm that it hasn't been changed in a long time, if ever. I've read the discussion above, but it doesn't tell me how to completely drain the two systems (engine; motor/electronics), or indeed, whether the two systems are, in fact, connected. Is the radiator petcock the only drain point, or is there a second drain for the motor/electronics system (and if so, where)? Even if the two systems are in some way connected, logically there must be a valve that separates them some of the time since they operate at different temperatures and pressures. Of course, such a valve would probably be open at cold temperatures, which would allow a single drain point. Knowledge is power, and I want to be a Marvel superhero before I start the job. pjc