2003 Grand Caravan P/S intermittent failure

Is the fluid level correct, no leaks? Sounds like the pump might be going out on you. Pumps usually only make noise if low on fluid or they are coming apart internally

Checking system pressure can help you determine the cause of the problem.

Just finished a p/s pump in a Toyota, so dont write off American cars just yet

A lack of power steering assist can be caused by problems in the pump or gear.
To do the pressure test
you must obtain manufacturer's specification for the vehicle, and a power steering gauge.
Install the gauge tool on the pressure side between the pump and the gear. Position the shutoff valve toward the power steering gear. Start the engine and record the presure in the straight- ahead position with the gauge valve open.
If the pressure reading is above specification, check for restricted hoses or a damage steering gear.
Next, turn the steering wheel full left or full right and hold the wheel against the stop for no more than five seconds. Record the maximum pressure attained and check factory specification. If the pressure is below specification, position the steering wheel in the straight-ahead position and slowly close the shutoff valve. If the pressure rises to proper specification with the shutoff valve closed, the pump is working correctly. Look for problems in the hoses or gear assembly. If the pressure does not rise with the shutoff valve close, the problem is in the pump. If the pressure is ok with the shutoff valve closed but fails to reach sufficient levels when the steering wheel is turned full left or full right, then the steering gear is faulty.

You're welcome :)