Tractor Repair: International 560 hydraulic problem, lever valve, double acting cylinder

Question
Dear Sir,

 I have owned this 1960 International 560 for about 3 years.  It has a Koyker quick attach loader and a double acting cylinder on the rear for 3 point lift.  It has a 3 lever valve for bucket lift and tilt and rear 3 point lift.  Last year I began having trouble with the hydraulic system.  It would take 5 minutes or so to 'prime' and then would be ok as long as I didn't wait to long before using hydraulics again.  If I waited too long or let it idle it would lose prime and I would have to wait again.  I put up with it as I was not using the tractor much but now that has changed.  Just recently things changed.  Now I have instant hydraulics all the time but I can tell the pump is putting out high pressure all the time and whatever kicked it out after the lever went back to neutral is not working anymore.  This puts a continual load on the motor and I'm sure is not good on the pump.  I'm not a novice at mechanical repair but not an expert either.  I would like to attempt fixing it myself to save money if I can get a diagnosis.  It has good hydraulic power when I need it.  Is it time for a pump replacement or is there a diverter valve in the system thats bad?  I also replaced the hydraulic filter and cleaned the screen last year.  It was pretty dirty.  I have ordered a service manual on it but haven't received it yet.  I thank you for your time on this.  If I can't fix it at least I can talk intelligently to the service man when I take it in for repair.  Its a great tractor and deserves some attention.  Mark.

Answer
Hello,


  I don't know why it doesn't take time for it to prime now, I can't think of a reason why that would change, but the hydraulics staying on high pressure is a separate issue.  Make sure all the levers are returning to neutral.  The main cause of staying on high pressure is the rear hitch not cancelling out when it is raised all the way up.  Usually a worn or bent linkage.  It's definitely not good for the pump to be on high pressure all the time.  It can cause the oil to overheat and also wears the pump out faster.  Losing prime sounds like a suction leak problem.  Either the filter cover or a bad o-ring on a pump suction tube.