David,

Can you elaborate a little more on the term air? Is it air bubbles (a few mm long one after another) or is it thousands of tiny air bubbles that appear foamish? I know that metal geared pumps can create that foamish type appearance when running, especially if the the pump pumps the fluid faster than it can draw. If you can easily remove the festo fittings and re-test I would start there and then work your way to the pump. Any pictures? Good luck. Ken