JD 690E LC How do I determand if the Hyd leak is the rotary swivel or swing motor?

I bought the JD 690E LC. It has a bad hydraulic leak under the rotary table. How do I tell if the leak is from the rotary swivel in the center of the machine or the swing motor seal?

Would the machine still move correctly with some of the rotary seals leaking?

JD 690E LC How do I determand if the Hyd leak is the rotary swivel or swing motor?