[Bimmer750i]

So after having my 2014 750i 4.4 for 6 months,
I took off the plastic turbo cover under the hood and saw a reservoir.
I opened it and saw it was empty.
I started digging around in my owners manual and there was no mention of this thing anywhere.
After a online search I discovered that it was a coolant reservoir for the turbo coolant pump.
I added yellow concentrate.
My questions are ,is it suppose to circulate(I can't see it moving coolant)?
Secondly how can I tell if my pump is bad?
I heard that the pumps were prone to failure.
Why is there not a level sensor in this tank?
By all accounts,bmw manual doesn't know it has this pump.
Any info could be helpfull,please and thank you.