Ford 1996 Windstar Manual page 339

Do not let the reservoir for the master cylinder run dry.
This may cause the brakes to fail.
Power Steering Fluid
Check the level of the power steering fluid at least twice a
year (i.e., every Spring and Fall).
To check the level of your power steering fluid:
Start the engine and let it run until the power steering fluid
1.
reaches normal operating temperature. The power steering
fluid will reach the right temperature after at least five
minutes of idling or at least one mile (1 km) of driving.
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.
Servicing Your Windstar
RWARNING
339