Something leaking at the steering rack

Fountainhead

I've read that you don't want to adjust that nut unless you have factory training and / or some method to verify the adjustment is within tolerance.
I have no leak significant enough to warrant messing with it, but mine is wet and dirt adheres to it. I just wipe it off every couple of months.

I've also read on these forums that Nissan incorporates speed adjusted Power Steering that tightens or loosens the turning resistance depending on speed of the vehicle.