I bought a '01 with 128K recently from a family friend. he had it detailed before trying to sell, so everything was cleaned up when I acquired. About a week after purchasing there was a drip off the front tow hook on the drive. Leaking fluids is one of my pet peeves, so I crawled under there. Traced it back to the power steering reservoir. Thread searched on here and determined that the supply and feed hoses have a tendency to leak on this age vehicle. I bought the hoses from a Toyota house that deals over the internet ($60) and replaced.
Before I got to that point, I took the thing to the car wash and hit it hard with the engine degreaser on the fluid reservoir, the rubber hoses up top, the pump and all the frame that was wet with the fluid. I waited a day and then started checking where the fluid was coming from and determined the crappy clamps and old hoses appeared to be the likely suspects.
I removed the battery from the X to give me more room to work, but still this is a tight area. I used the worm-gear clamps on the new hoses, and took it again to the car wash to remove the fluid that went everywhere during the removal. I had my large, flat drip pan under the X to catch the drips, but it was/is a mess getting this off, even after draining the reservoir with the turkey baster. Checked it again every day for a week until I was satisfied that problem was gone.
This is my first Nissan, after owning Honda's, Toyota's, Jeeps, GM products.
I did the thermostat on the X and then the power steering hoses, and my opinion is that Nissan's (or at least the X) is about the tightest workspace vehicle I've tried to turn wrenches on.
One thing I did learn the hard way was that the reservoir will come out of it's mount by pulling it straight up without removing any bolts to allow you to get to the hoses on the bottom. Likewise you can clamp the hoses on it before you put it back home....heck of a lot easier than trying to remove/install the clamps while it is mounted.
Good luck to you !
PS ....I noticed my pump has just a little bit of whine to it, do you have that too?