JD310A loader bleeds off quickly when empty. But does not bleed off when loaded. loader and hoe operate slowly but have plenty of power. It will hold its self off the ground without bleeding off. backhoe never bleeds off, just loader. i have changed filters and suctioned screen. New hydraulic fluid. PLEASE HELP
Since it doesn't bleed off when loaded my guesses are piston packing in one or both cylinders, and/or a check valve or o-ring in the loader control valve. Try lifting the loader up empty, shut the engine off, slowly remove a hose from the rod end of the cylinder with a bucket underneath. If you have oil coming out of the cylinder as the loader boom drifts down, or the open hose end, you have bad piston seals. If not then the problem is in the loader control valve section somewhere, start with the check valve and plug in the two ports, bad o-ring could cause it or a check ball not seating properly.
thanks for your help i tried lifting and taking hose off with no fluid coming out as loader bleed doun but i dont see how it could because if it is bypassing the rod packing it would just pass to the other side of the piston and and all fluid would remain in the cylinder???? justt a theory maybe i am not understanding it your help is greatly apperciated thanks
don't think are understanding the previous post
ok i did as was suggested loader up engine off removed line and no oil leaked out as it bleed down so i assumed the oil was bypassing rod packing and staying in the cylinder what would cause it to come out, seems it does not matter if the rod is moving down the fluid would remain in the cylinder but just on the other side of piston as it bleeds past packing the cylinder will continue to hold the exact same amount of oil regardless of where the piston is in the cylinder,i thought it would not push it out if it is bleeding by,anyway i probably just dont understand but i did exactly what was suggested with no fluid leaking so i guess i should look at the valve now????? thanks for everyones help
yes
ok i just got the valve off and one of the orings that seals around one of the plugs was wasted does anyone know if that is a standard round oring or something different than a standard oring ( flat or has a lip or something?) thanks
Should be just an o-ring, but may be a special size and cross section. Double acting cylinders hold more oil on the open side of the piston than they do on the rod side, because the rod takes up space. If oil leaks by the piston seals there will be more oil than the rod side can hold and it will pour out of the rod end fitting. Sounds like maybe you found your problem, let us know!
ok thank you for helping me understand i didnt factor in the rod displacement it all makes sense now i will let you know what it does after i reseal the loader valve thanks for all your help
thanks for your help now i have all new seals in the loader valve but i foolishly mixed up the boom spool and the bucket spool not sure which is which??? one looks to have 2 poppets inside the spool and the other only 1 poppet in the spool hmmmm not sure also 1 spool has all round holes through it and 1 spool has a couple oval holes through it cant i looked at jd parts catalog and cant identify my spools and no part numberson my spools please help thanks