Hi everyone. I am attempting for the first time to replace my water-cooled alternator on a 2001 x5 4.4i. Can someone please explain to me why the instructions I’m finding online state that the coolant needs to be drained first? What will happen if I just change the water cooled alternator without draining coolant?

If I’m supposed to drain the coolant first, instructions state there are 2 drain plugs. I found the one under the radiator but where is the one on the engine block and how do I tell if it’s the drain plug?? Is it easy to get to? If not easy any suggestions?

Thank you
X5 DIY Beginner