Modern cooling systems are complex.

The Boxster/Cayman cooling system has 6 vacuum operated valves, controlled by the engine ECU.
To fill the system the car has to be connected to a Porsche external computer and coolant added as instructed, with waits at certain points. The engine is then started and as heat grows the computer will instruct the technician when to add further coolant. The process takes about an hour.

I suspect that the BMW engines in the CX cars are no less complex/demanding.

DIY friendly they are not.

Peter,
66, 2016 Porsche Boxster S
No longer driving Tarka, the 2014 Plus 8...