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Discussion Starter · #1 ·
Our JD 7400 can't lift the 678 corn header all the way up ,our dealer can't seen to find anything on how to get the pressure up in the header ram , the pressure is only at 600 psi ,should be at 3000psi , had the valve off ,checked everything i know off , hoping some of you guys can help me , been a long time reader of this forum.
 

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Had this problem on 7500 it only worked until oil got hot and then had to jerk back and forth on hydro and get chopper bouncing for it to lift the header. Boss said we were to busy to shut machine down and fix until the final drive bolts let loose and wheel fell off. I believe that we replaced the valve that's inside right frame and fixed the problem. Sorry don't remember part name.
 

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Pressure relief valve. Ours was faulty the other way one time. Charged the entire machine with full pressure from the pump. It wasn't relieving the system at the 3000psi. Wreak havoc on hydraulic system.
 

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Discussion Starter · #4 · (Edited)
@Hilltop1 that's we have to do jerk the machine back and forth, would that pressure relief valve be right where the header valve is, on inside of the right side, cause our dealer can't seen to tell us where that valve is, or is the header valve together with that pressure relief valve or is it that value block near the engine on the right side
 

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DE19756 or DE19755 one of these should take care of it. search in the where used to see where they are located. hard to know which one with out the schematic
 

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I think inside right frame rail someplace, maybe behind the blower??? I don't remember exactly. I think one time we hit it with a hammer and it worked one time. A half hour before wheel fell of 7500 from bouncing the motor let loose in 7800. It was not a good day that day.
 
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