Try this even if your rack is quite "sticky". It won't work if the rack is leaking. If the pump is making noise, replace the pump and try the steps below.
First the theory, the pump overheats the fluid which then fails
as a lubricant, causing the pump to wear putting particles in
the fluid which wreck the rack. The solution is to overkill the
problem. Get higher temperature fluid, filter and fluid COOLER.
The best fluid that is easy to get is Mobil 1 ATF. Power steering
filters are a little harder to find but several are out there.
(try IPD, the VOLVO people) Use a cooler off the trans of an auto
XR, PS cooler off a big 'ol lincoln, or anything from the yards.
Put the filter and cooler in the return line. The cooler fits
nicely in the bumper in front of the tire. After putting the parts
on, there is 2 ways to flush the system: one cheap, fast, and
tricky; the other not.
Elegant Method, remove the return line off the reservoir,
and plug the end of the reservoir. Place the return line into
an oil drain pan.
Pull the coil wire off, so it wouldn't start, put the pedal to the floor (to disable the injectors) and crank the motor while turning the wheel back and forth. Then get out, refill the reservoir, and do it again, until the fluid comes out clean. You can do this by yourself, just keep an eye on the reservoir.
Use a gallon of cheap ATF, ran that through, then put in the good Mobil 1 ATF at the end. No sense wasting Mobil 1 during the flush phase.
Method 1 is to fill the pump with Mobil 1 and put the return
line in a 1 gal or so pan. Turn the steering wheel full lock.
Start the motor and while your friend is turning the wheel lock
to lock you are pouring fluid into the pump resivour. Keep turning
and pouring until a pint or so of CLEAN fluid comes out the return
Method 2 is to fill the pump with mobil 1, start the car and
turn the wheel lock to lock. Fill the resivour as required. Drive
around the block both ways to turn the wheel some more. Use a
"turkey baster" to suck out ALL the fluid from the resivour
and refill with more mobil 1.
Repeat until the fluid is clear. In a week or so check the fluid and if dirty at all, repeat until clean. After a few months repeat again.
For both methods, check fluid clarity every year and replace if dirty.