After sitting for a month, the steering on my 89 240 now binds when beginning to turn and varies in stiffness. It has improved somewhat but is still very stiff and binding, particularly when starting out. Revving the motor does not affect the symptoms, so I doubt it's the pump. There are no noises or leaks and the steering has always been responsive and tight. I have never changed the power steering fluid and the color is very brown. I suspect it's in the rack and wonder if changing the fluid would help. If its not the rack are there other components that could cause this?