Bought my 11/2016 MS 75D In August 2020. The same buzzing when awake has always been there since I got the car. Only stops when the car sleeps.
I work in power plants, and to me this sound is the same sound a hydraulic pump makes, so I assume that there is cooling pump running all the time (when awake)
I am attaching an audio file I made in the frint RH side wheel well while I wake the car up by opening the app.
The buzzing in the last ~10s of the clip continues anytime the car is awake.
After a few months of owning the I had a loaner, a 2018 MS 100D and it did not make the same loud buzzing.
So when I took the car in for FSD upgrade I pointed out and they ran cooling system tests, told me everything is running as it should and there are no issues.
However the vampire drain when the car is awake is quite large and I can tell a big difference in the warmer months vs cooler months (I'm in FL)
Range loss in the summer time, when temperatures are in the 90s daily, is 5-10% /day. 10-20 miles a day.
Basically it will be 3-5% loss from when I get to work to when I leave, and when I'm out of town and can't charge overnight, it will be another 3-5% loss from evening to morning. Since I've had the car over a year I have noticved that in the cooler months (november-april) vampire losses are minimal, so I definitely attribute it to the car staying awake longer in the summer to run this coolant pump.
Unrelated to this thread, but I have the front RH speaker making a buzzing soundm, and the pitch of that sound matches the coolant pump sound.
So far 2 different service centers can't identify the speaker buzzing issue because it is intermittent... I almost believe that there is a grounding issue with this coolant pump, but that's my opinion... I have attach a video of the sound from the front RH side wheel well to the speaker.
Buzzing
Wake up sounds and buzzing
external buzz to speaker