Helping a friend out with his older case machine. Serial jjg0165745. All his hyd cylinders seem to drift down on there on, all cylinders have already been resealed except outriggers , but they seem to work fine an not drift down. Sometimes the front loader will hold on its on an sometimes if ya hit the bucket tilt the loader mite start to drift again, can’t really pin point the issues due to the rear hoe functions drift down slowly aswell when sitting an running, an front loader will not pick the machine off the ground either . Never seen an older machine do this, normally it’s either the rear or the front control valves acting up but never seen both together. Any ideas
Hey Chris; have you checked the main relief pressure on this machine?
No sir we haven’t, I have purchased a service manual of it. Just twiddling thumbs waiting on it. Was hoping someone else had seen my issues with the cylinders drifting down. What’s got me puzzled is the fact that the rear hoe is firing it aswell. An it’s a complete differ valve body an circuit ?
True the BH valve is separate but they use the same main relief which is in the loader control valve.
Not sure what a Super King is. 580 Super K is closely related to a 580K? Most models are Construction King. That said, I wonder about port reliefs. Your relief valve is limiting oil pressure flowing into a cylinder. Once raised, the valve closes. Oil in the cylinder is constant. For example the boom; it might take 3500 PSI to raise the boom with a heavy load in the bucket. Then you extend the dipper, & raise the crowd. Pressure inside the cylinder rises sharply because of leverage. 580K has a bypass valve built into the piston in the boom cylinder. Other models have port relief valves in the control valve. If these valves get a tiny bit of debris in the seat the component will sag.