Cadillac Repair: Power steering, power steering pump, shaft seal

Question
I have a 94 Cadillac Deville,4.9 liter engine.The power steering pump was making noise and leaking slightly from what seem to be the shaft seal. There was also an error code in history, saying that the power steering pressure switch was open. I replaced the pump, I did not flush the lines or empty the reservoir. I am still hearing the power steering whine.Do I need to flush the old fluid? Or is something else going on?
    Thanks
        Terry

Answer
You should always flush the system before installing a new power steering unit.

However, Most people do not and it is not unusual for a new power steering pump to make noise until it purges out all the air from the system which may take 2 or 3 days. Just keep driving it.