If the reservoir is full and the pump still whines, I'm thinking your pump is going out. Time to replace it. But, to purge it, make sure the reservoir is full and then turn the wheel lock to lock a few times.The power steering fails at what seams at idle and low rpms. The fluid checks out fine but the pump whinds like there is air in the system. Has this problem occurd to anyone?
Answers on how to purge power steering system?