Case 680k Backhoe

[swax]

My 680k has an hydraulic problem. When the front bucket is on the ground the backhoe is weak. It will only have good power if the front bucket is off the ground.

 

[AJ.]

Are you sure the levers for the front bucket are returning to the neutral position when you raise the front of the machine,the loader has priority over the backhoe,if a lever was not returning to neutral properly it would be robbing the hoe of power,there is one pipe adaptor should the o'ring blow on it the pressure to the hoe falls,rather than try and explain it is marked in the parts drawing above,the main valve could have an issue,use a deep socket to remove it without altering the setting,but to save yourself getting oil in your face ckeck the levers or more importantly the valves that they attached to are returning to neutral esp if you got return to dig etc.
AJ

 

[swax]

AJ, I did suspect the loader valve as being in need of service. I do have the service manual and the area you suggested was the most likely suspect. I purchased all new o-rings and rebuilt it several years back but problem was not solved. I must raise the front bucket off the ground in order for the stabilizers to lift the machine off the ground. However I am sure the front bucket valve is in a neutral position when problem occurs.I do have the return to dig control but never used it. It does seem like a simple problem but thus far hard to find. Thanks

 

[AJ.]

I understand your problem a little better now,you are saying that the stabilizers won"t lift the machine if the front bucket is on the ground,when the bucket is down the lift is much greater than when the wheels have the weight and act like a pivot,you need to check the pressures on the machine,all backhoes will lift the back up quicker if the front bucket is up,if you have a guage put it on and see what the pressures are like.
AJ

 

[swax]

Wow I never would of thought that? The front bucket lifting capability is excellent.So their are two hydraulic pumps on this machine. I do have a pressure gage for hydraulics so I could test that. Actually if I new it was the hoe hydraulic pump and the problem would go away it would not upset me. Just so you understand what I am saying : With the front bucket down machine may get rear tires an inch off the ground with a strain. Front bucket up any height off ground machine rear well go up to fully extended stablizer cylinders no problem.
Thanks