2020 CX-5, 2.5 L AWD non-turbo; 93k KMs = 58K miles

Currently has a quiet, constant, high-pitched whine / hum noise noticeable upon start up, idling and after shutting vehicle off. Began about a week ago. Noise is present before and after short or long trips. I thought it might be a cold winter thing affecting a fan as temps have hit - 25C = -13F and now recently around 0 C = 32F but engine can be cold or operating temp. Cannot hear it inside while driving / accelerating or decelerating. At first I thought it might be engine fan cooling off but it occurs upon start up from cold.

Replaced rear diff and front transfer case fluids 8 months ago (9K K = 5.6K miles). This noise is new and I can't quite tell where it's coming from. Car is operating normally. No other unusual or noticeable changes.

Thoughts / ideas on where to start diagnostics? I'll try to add a sound bite.

Thanks.

 

"start up, idling and after shutting vehicle off"
A noise is not something that can really be diagnosed on a forum.
Sure, you'll get a bunch of "it could be this or that" but do you really want to run through them all?

For example: this time of year I use to start my BMW K1200GT motorcycle every couple of weeks in my garage to keep things lubricated while waiting for the snow and ice to leave.
One day I had a terrible rattle and squeak on start-up. Then I blipped the throttle and two mice and sunflower seeds flew out of the exhaust and hit my garage door.
They had built a nest in the catalytic converter. I have also twice found mice and chipmunks under the engine cover on my CX-5 in the fall and winter after it had set for only a couple of days.

I'm not sure why you are thinking diff/transfer as they don't run after shutoff.

 

I had to chuckle at that. Death by garage door impact. Or at least injury with a blunt instrument.

Agreed, sounds are difficult. I mentioned the diff because apparently it's a cause, but in hindsight, only when in motion which is not in my case. I will try to upload audio.

 

Normal start up sounds of most all Skyactiv 2.5 gas engines that are all normal..
This is cold start outside temperature 39F engine cover removed

https://
VID 20210803 121551614

 

Tools need many times to pin point sounds origin

 

is it coming from one of the front headlights? Or more from the rear? I had to replace the headlight fan and the differential on my 2022.

 

Oh no...reminds me of the South Park episode and Cartman's Alien probe....

 

Love calisto's screwdriver extension.
If your mechanically inclined you could try taking off the serpentine belt and running the engine for a very short time and if the noise is not there you then have to play a bit turning all things driven by the belt like the alternator etc.

 

My 2024 CX5 has a similar noise, the noise sounds like a small fan running and I can only hear it while standing at the front of the car. This noise last about 20 seconds after shutting engine off. Cold or hot weather short run or long run make no difference, every time you shut engine off the noise happens. And it is not the fuel pump,

 

I always enjoy when out of the blue another member claims to have the same sound....

So you all know it winter you are using your defrosters so when you shut off the engine the fan will run for a very short while/ My point is that reading "i have the same whatever (any subject on any given thread) is more or less not helping the OP that started the thread and has the question? It is rare that 2 people can have the same "issues/problem ( I choose those exact words) because of all the variables between owners.

IMHO lets solve one members that is asking the original problem first and then other might pop in with their similar issue or start their own thread about a possible issue or question on their Mazda?