I see what you mean, but how did the oil blast away metal? If the oil got past about 500 degrees F, it would start to vaporize. This is far below the melting point of any of the metals involved.
By purging, you mean working out the air bubbles? From what I can tell from the Hydro Gear manual, you just have to run it for a little bit to work out the bubbles. If this is true, surely they would have worked themselves out, right?