I've been here before with this problem, now with a new twist. Vehicle
has 2.7 engine, +/- 115k miles on it. I've had an issue with
intermittent very hard steering. Changed the fluid, some relief but
the problem more or less went away until now. Had a wheel alignment
done as car was pulling to the right. Alignment seems okay but next
day the steering is like there is no power assist. Makes a noise when
you put turning pressure on the steering wheel. Opened the hood, had
the engine running and had my wife try to turn the steering wheel.
Pump seems to be running as I see oil swirling in the reservoir when I
take the cap off. Noise is coming from one of the smaller diameter
steel lines on the rack. I can touch the line and feel the vibration
which corresponds with frequency of the sound. Feels like a
restriction of some kind is not allowing proper amount of PS fluid to
pass to create assist. Happens when turning in either direction. Is it
the pump not producing enough pressure? If that'sthe conclusion,  how
can one check that definitively? Or is it a problem with the rack?
Driving it on the road is not an issue but pulling into a parking
place is like parallel parking  a duece and a half. Your thoughts/
suggestions are appreciated.