Turn the heat up to max when you do this so the coolant in there gets circulated.

When you have the radiator out, hose the A/C condenser out from the engine side towards the front of the X5. Likely lots of "stuff" will come out.

Buy BMW coolant (or equivalent like Mercedes Benz) not some cheap crap or orange stuff that is supposed to last 100k miles. Get the factory type as it is most compatible with the plastics BMW uses (high recycle content, easy to recycle stuff).

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Kirk
Las Vegas
2016 X5 40e Mineral White/Black Dakota Leather, ZLL, ZCW, ZDA, ZDB, ZPP, multi contour seats, rear side window shades, HK stereo
2011 E90M3, 6-speed manual