Tractor Repair: 1956 international tractor, seal leaks, model tractor

Question
When I run my tractor for awhile and then stop. The Hydraulic fluid runs into the oil. Could you tell me what I need to do to stop this?

Answer
  I don't know what model tractor it is, 1956 must be the year.  Whatever model it is, it probably has an engine mounted hydraulic pump.  If the pump seal leaks, hydraulic oil will go into the engine oil.  The seal will have to be replaced, or if the pump is worn out, the entire pump will have to be replaced.