Ford 1998 Windstar Owner's Manual page 286

While the engine idles, turn the steering wheel back and
2.
forth several times. Make sure that the cap assembly is
installed at this time.
Then turn the engine off.
3.
Check the fluid level in the power steering fluid reservoir.
4.
The power steering fluid cap
If the power steering fluid is low, add fluid in small
5.
amounts, continuously checking the level, until the fluid is
between the minimum (MIN) and maximum (MAX) lines on
the dipstick. Do not overfill.
Make sure the cap is free of all dirt prior to re-installing to
6.
prevent pump damage.
Maintenance and Care
287