Thanks for the detailed description!

My respect for doing this in -15 degrees Celsius. I would not do ANYTHING on my car in such conditions unless the risk of having unmovable car would be imminent.

Actually - my radiator also has this pink/white crust on 2 places but as long as I do not need to fill anything in the reservoir I do not care. Well... once I started to think about changing the radiator (just to be sure) but that A/C radiator next to it scares me. I still cannot imagine how to take the engine radiator off without harming the A/C one, even with your DIY.