I just cant seem to do any maintenance correctly today... So I wanted to replace my coolant today. Looked on here for the DIY found a few that were similar but not the exact same. Figured it was simple enough and went to it...

I have an 07' X5 4.8L

I took the splash guard off

Put a bucket under the blue plastic radiator drain plug

removed the plastic drain plug and let the coolant drain out.

Put the plastic plug back in, and refilled the coolant, gave it a couple minutes to fill cavities in radiator and then topped it off again.

Went for about a 10-15 minute drive and I noticed my front driver brake was squeaking. I just put new pads on it last night so I figured I got a spot of grease or something on the rotor and that it would go away with time.

I pull back into the garage and noticed that its leaking coolant/has coolant all over the front drivers suspension and that's whats causing the brakes to squeak

Thought, "I must not have tightened the drain plug all the way and its leaking"... So I take the splash guard off again and its bone dry and perfectly tight...

The leak is coming from somewhere in the engine bay but I cant see exactly where. I THINK from under the expansion tank? The coolant level went from "MAX" to "MIN" in about a 10-15 minute drive. So its leaking pretty good...

I topped it off again and its parked for the night. Could someone who knows more than me tell me where I screwed up and perhaps a starting point on how to fix it? I'm worried it's overheating for some reason and I cracked the expansion tank

Go ahead and let me have it, I deserve it today.