More then likely this is the pump failing. These noises are normally caused by two things, either air in the system or a failing pump. If there is a leak allowing air in the system then this would cause a whine and could cause the pump to fail. However, your fluid being full points to a pump itself.
If this issue has just started or started getting worse then I would go ahead and replace the pump if the fluid is full. The only other thing you will want to check is if the fluid is foaming or bubbling when you turn the wheel back and forth. If it is, then it may have a leak where it is pulling air in and the foam you are seeing is the air escaping through the reservoir.
Let me know if you have questions. Thanks
Images (Click to enlarge)
Wednesday, May 6th, 2020 AT 4:24 PM