Is there a easy test for cylinder bypassing..... I have a front loader bucket dump cylinder on a cat 416c backhoe (std version single cylinder) that is nice and dry but wants to dump the bucket at 70% lift height without dump control input......i suspect a bypassing issue but do not know how to test without taking the cylinder off and rebuilding it.....(4zn021xx) any suggestions...hints...etc.. thx in advance
Regarding the words "without dump control input".... are you referring to no control input by you, or are you referring to the control input the machine provides as the bucket elevation reaches the maximum portion of the range? The machine typically has a feature (eg linkage) to level the bucket otherwise material will spill over the back onto the hood. If this motion seems excessive, perhaps an adjustment will be satisfactory?
Does it settle into the dump position when holding at other loader height positions. If not it does not sound like a cylinder bypass problem. To test a cylinder for bypass on the center packing gland. Secure the bucket in mid tild and hold Congolese against the bypass. You usually don't need a lot of throttle for this. The leaking past cylinder will very quickly get warm or hot at the spot the internal gland is located. I think you have a control corrordination issue.
thx for the replys.... oceanbob......this does occur in the general height range that would require load leveling...all linkages associated with load leveling have been either disconnected or otherwise disabled...i am not aware of a specific adjustment...a load leveling fuction issue was my first thought ... old-iron-habit will do and check cylinder for warm spot........this problem seems to be associated with loader height and bucket position and not associated with control imput or position...this is a older mechanicaly spool driven control system and linkages are intact and in good shape..
You can also activate the Cly all the way in or out and remove opposite hose , plug the hose , and pressurize the hose still hooked to Cly and if oil comes out the fitting on the Cly the piston seals are bypassing. If there is no bypass check the other Cly. If it does not have bypass you likely have a weak relief valve.