grandpa Love

Well-known Member
John from LA and I worked on this hydraulic issue on my 640 the other day and one picture we didn't have an answer for. Is fluid supposed to leak out of the small hole? It leaks a little until something comes out and it stopped leaking. Also ,new today, I left bushhog raised about 12 inches off ground and it held there for 24 hours. None of our other tractors will hold up for even a few minutes with tractor off. But......it would not lift any higher until we bled a bunch of air out of pump. Where in the heck is the air getting in at ? Not losing fluid anywhere. I'm lost. Thanks.
a174637.jpg
 
That hole is the small end of the unloader valve. It is metal to metal "seal" (no o-ring or such, just a very small clearance), so should expect some very small leakage. Where does air get in? On the suction side of pump, starting at hydraulic sump, you have the tube thru the transmission/bell housing, the gasketed interface to the manifold connecting to pump, the same at manifold/pump interface, the shaft seals in the pump itself.
 

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