I just noticed a rattle/humming sound when starting my 2015 Toyota Highlander. It happened 3 times, all in the last week or so. It could be cold-related (around freezing temps). It sounds like some electric motor, similar to what a large computer fan would do. From the cabin, it was clearly louder than the rest of the car engine. Car heating and fan was off.
I immediately parked, and it continued for about 5 seconds, when I stopped the car, after cutting the engine. So, I ruled out:
- rattling object in the car
I assume there is some pump or other component that could produce this sound. Pump that maintain oil pressure, maybe ?
I'm wondering what those components could be ? How critical could such a sound be, e.g. how urgently should I go back to the mechanic/dealership ? There are no check-engine lights or anything else indicating a problem.
Edit: regular V6 engine, not hybrid or anything.