Metallic Grinding Noise After Starting

[PersephoneJade]

Hey all, I'm back! I figured since my last thread apparently got a lot of views that I would start another for a new issue I am having. /joy

So... I have a '05 Murano SE and now has 92k miles on it. I was most recently on this forum for help with an engine rattle. After a very long time and numerous visits to different mechanics that particular issue seems to be resolved.
Recently there was a whine (not the rattle from a previous thread) in the engine that we couldn't place. Took it to a recommended mechanic and they said that it was something in the transmission but nothing that they would worry about.
Last week, while backing out of the driveway I heard a grinding noise (whine still present) coming from the engine when I turned the wheel and accelerated to drive down the street. It was alarming, but as soon as the car straightened out it stopped so I thought maybe I had cranked the wheel too much.
A couple days later I started the Murano and heard the same grinding noise (a couple seconds after releasing the key) but this time the car was parked. It lasted maybe 30 seconds and then stopped, but the whine remained. The grinding noise also only happened after the car had been sitting over night outside.
Even though it was not quite due for an oil change, we did the change this weekend anyway. If it matters any, we use full synthetic 5w30 oil - and of course the filter is new. Upon the oil change, the whine in the engine went away but the grinding noise stayed.
Starting yesterday, the grinding noise started happening on every start and lasts longer on the over-night starts in the morning. As the engine warms the noise volume decreases and will eventually go away but this takes 10+ minutes in the morning.

There are no engine lights and after the grinding noise goes away, the engine sounds normal. Other places I have looked at online have suggested the power steering pump and that the steering fluid may be low. Is this possible for the noises that I am experiencing on just starting the engine without turning the wheels/steering wheel?
I am looking for some suggestions on avenues that I can check into before taking the Murano back to a mechanic or having to travel at least half an hour away to a Nissan dealership - and I am not even sure they have a service department which means a 2 hour one-way trip to a dealership with a service department.

If additional details are needed, please ask. I am anxious to figure this out before something happens that would require thousands of dollars.

Thanks again!

[PersephoneJade]

I had someone else confirm the power steering pump/fluid is the issue. Today I checked the fluid level and found it to be incredibly low. I filled it to the correct level for the temperature of the engine, and when I started it the noise was gone. Until now I never knew that PSF was used as a lubricant when starting an engine. The engine sounds as it should now, and hopefully I will not have any troubles for a long time.