Tractor Repair: HI 300 U Hydraulic prob, crank case, hydraulic pumps

Question
QUESTION: i have a gas 300u  has been sitting a while runs well  
having a prob with hydraulic system building up to much presure   will plow seals in pump and dump fluid into crank
case any ideas will be helpful
         thanks  Matt

ANSWER: The pump is probably worn out, causing too much oil to bypass and over pressurize the seal.

---------- FOLLOW-UP ----------

QUESTION: when i bought the tractor about 15 yrs ago this same thing happened  i changed the seals  fluids  allwas well  didnt use a great deal  parked for  last 8 yrs  started now and then    this last time i started it it firstblew oil out of the gasket beteen the hydraulic pump and the distributor  moved the up down leaver and it stopped leaking  used the tractor a little  brushhoging  parked it next time i stated it it dumped the fluid in the crank    i thought may be the by pass in the up down leaver was sticking  or may be a relife valve not opperating correctly   if you still think the pump let me know   thanks again  matt

Answer
It sounds like the hydraulic levers may not be cancelling and returning to neutral, causing it to stay on high pressure all the time until you moved the lever.  But even so, staying on high pressure should cause the relief valve to blow and not cause any damage to the pump.  Although the relief valve blowing constantly can cause the oil to overheat.  If a relief valve would stick and not relieve the pressure at all, it either splits the pump in half or blows a hose because the oil has to go somewhere.  The hydraulic pressure should be checked with a gauge to make sure it is correct.  If the relief is opening but at too high of a pressure, it can shorten the life of the pump or cause it to leak.  I have seen hydraulic pumps leak oil into the crankcase when the seal was the only thing wrong with it, but that is extremely rare.  It is normally caused by the pump being worn out internally, and the excessive clearances  allow more oil to the seal than it can withstand, pushing oil past the lip of the seal or pushing the seal right out of the pump.  In that case, replacing the seal is only fixing the symptom and not the problem, and it will happen again.  The pump should be disassembled and checked, and if the gears have worn a groove into the inside of the pump housing, the pump must be replaced.