I went and bought the Harbor Freight Cooling Pressure tester. The black adapter worked perfect. Put 12 psi (cap pressure) and it held with no leaking. I even removed the oil cap if that makes a difference.
Is it possible I just have a bad cap and the PO put oil in the overflow tank by mistake?
What are your thoughts guys?
https://youtu.be/5IYbhv-xGpw