Electric motor noise when put in drive

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Humming when at a stop or under acceleration?
Actually it happens when I shift gear from p to drive or reverse, you start hearing so sort of electric buzzing, or a vibration and pump noise. It was there when we got the car but now it it is louder.

The sound comes from the front hood and when the car is not in motion.
I get a loud humming or buzzing noise from what might be a pump when I get shift to drive. Can someone help?
Could it be the vacuum pump for the brakes? Does the noise go away after a few seconds, but return when you pump the brake pedal?
Could it be the vacuum pump for the brakes? Does the noise go away after a few seconds, but return when you pump the brake pedal?
I doubt it is the vacuum pump for the brake.

Actually I was thinking of the cooling pump on the coolant circulation. But what confused me is it goes away after a few seconds. Not sure now if it is electric humming or buzzing, or it is from battery coolant pump. Does anyone one know how the cooling pump is located at? And how does it look like? Part #?

Does anyone have a manual?
Well, there are 3 coolant pumps. one seems to run all the time that the car is turned on, or is charging. When coolant pumps cavitate, they make a rattling sound, like BBs in a can sound. If you search my name and "service manual" you should find a post that has a link to a google drive service manual.
Thank you Heima for valuable info, I tried to search it, unfortunately I couldn't find it.

But how could the pump cavitates if the fluid level is full. Or is there a chance for air to be trapped in the coolant system and not to bleed itself?

Is there a procedure for bleeding?
Do you suggest to change the coolant, the car has around 45000 miles?
Yes, air can get trapped in the many feet of coolant lines.

There are two ways to get the trapped air out of the coolant lines:
1. Use a coolant vacuum purge tool.
2. Use Forscan to run the pumps at 50% with the valves at the middle (0) position as seen in Forscan.
I do both 1 and 2 simultaneously.
I do not believe it would be necessary to replace the coolant, unless something happened to contaminate the coolant, such as mixing the wrong coolants together. Ford advises to replace the coolant filter when the coolant is replaced. It is beyond me why there is a coolant filter.

Here is the link for the service manual:

I just downloaded it and was able to install it no problem.
It is beyond me why there is a coolant filter.
Because the battery is stupidly expensive and clogged cooling channels would be a nightmare.

I know there shouldn't be anything in there, but even a hose replacement that has some loose rubber bits would be a problem. Add in the fact that diverters can crack and impellers can shatter inside the loop (I've had both, yay) I'm VERY thankful they included it.
Maybe so, but Tesla doesn't have a coolant filter, nor a battery desiccant (which Mercedes had added to the Tesla HV battery in the B250E) I don't think the Chevy Spark EV has a coolant filter, and it uses similar cooling plates as the FFE. I suspect that such parts are used as excuses to deny battery warranties if they are not replaced when specified to do so.
I'm not saying they couldn't get by without it - but they were low volume first gen tech demo platform conversations that doubled as compliance cars for California, there's a bunch of stuff that could be way better. A better-safe-than-sorry coolant filter in front of the battery is pretty low on that list. Not sure there's even a replacement interval on it, is there?