I've had my 2014 WRX for about a month and just the past two days I noticed a fairly loud "hum" coming from the engine bay during initial startup. It lasts for about 10-15 seconds, then shuts off. I think it is coming from this component (see red arrow in picture), which has an electrical connector on it. Seems to be some sort of pump or fan or something like that. But I haven't heard it running for the past 3 weeks. It just started yesterday.
It has been VERY cold around here for the last 3 weeks... around 0 degrees F. But the last 2-3 days have actually warmed up quite a bit and it was 45 degrees today. Normally I would expect "weird noises" on the COLD days, not the warmer days.
Also, this only seems to happen after the car sits all day or overnight. I do not hear the noise if I let it rest for an hour and then restart the car, for example.
Can anyone tell me what part this is and what it does? Why would it be running now, just all of the sudden?