2005 f350 with 93 Cummins 12v powersteering problems

I have a 2005 f350 that I had my mechanic put a 93 12v in last summer with a DCS kit. I had the powersteering pump start leaking so I put a new one in it. Filled it, bled the system and it would puke all the fluid out after driving for 10-15 minutes. I even took it back to my mechanic and they put it on the hoist and cycled everything back and forth and bled things on the hoist but it still pukes all the fluid out after driving for 10-15 minutes. I'm just wondering if anyone else has had similar issues or knows what would cause this?