Hydroulic question ?

I am posting this for a friend who is having some issues with a 310a (not sure on the year model) John Deere backhoe .
The backhoe has sat up since last winter and the hydroulic system was doing fine at that time , but now it wont even lift the loader bucket 1 to 1-1/2 feet of the ground and barly has enough strengh to lift the hoe or the out riggers . It acts to me like it might have air in the system , but the pumps not making noise like air in it . The resivior is full (in fact over full) and he said it was hard to steer as well .
Is there a bleeder on one of these hoes that I can let the air out of if any , or is there some other way to do it besides cracking the lines ?
Could it have lost prime or something ?
Can a filter get stopped up that fast ?
All advice is welcome !
Thanks in advance , Dozer Guy

He has a stoppage in his system somewhere. Generally hydraulic systems are self bleeding. When a cylinder compresses or "goes in" the oil is pushed back through the return line and dumped back into the hydraulic tank where it's cooled and then sucked out again when a cylinder is expanded or "goes out".

He could have a faulty pump, dirt, rust or other debris in the hydraulic oil could have plugged up a spool or valve or he could have a kinked line somewhere. Seeing as it's affecting the boom and the outriggers I would start looking from tank to the pump to the cylinders. Make sure everything is clean (take it apart and clean it).

I'm not a mechanic but I hope that helps out a bit. There's far more lads far more experienced then I on this board that will help you i'm sure.

Good luck!

Could be the pump was gone bad or the pump drive has stripped or the pressure relief valve is hung open or the relief valve spring broke. Lots of or's there but its hard to tell at distance. I start with a pressure gauge on the line from the pump into the valve body to check pressure when you open a valve.

Something else I rememberd him saying , He said that the 310a engine would not start without a bolt being loosind on top of the hydroulic pump . Not sure if it has anything to do with the problem or not but I would just mention it just in case .
Thanks for all you advice guys ,
Dozer guy

Not sure if the 310 system is the same as my 410, but if it is it sounds like the pump isn"t going into stroke completely?

Closed-center variable displacement pump goes out of stroke when there is no demand for fluid. De-stroking valve in the pump controls this function. Mine also has a de-stroking solenoid that opens when the starter button is pushed.

Check the operator"s manual...does the shuttle control have to be on forward or neutral( with engine clutch engaged)? The 410 has an engine driven hyd. pump that is charged from the trans. pump. Is the 310 the same or is it mounted inside the trans/diff. housing? Seems like the 310"s had to have the engine clutch engaged or else you would only have a few seconds of operation before the accumulator emptied and everything slowed or stopped?

My flow divider has stuck on occasion, also. When that happens, either I have no loader functions and no power steering but the hoe works OR the hoe won"t budge but I will have loader and power steering. Never had is stick in the middle( yet). Suspect that might cause a very limited flow( if any?) to everything?

My 410 be a test port on the pump. Stick a 0-3000 psi gauge on it, run it at 1500-1800rpm and watch the needle while someone attempts to clcle the loader, hoe and steering. Gauge should only show charge pressure until a control is cycled then it should jump up to full system pressure until the control is released when gauge should then return to charge pressure.

Hope I"m not forgetting something? A full set of manuals is a must for these machines. Good luck.