When digging with the backhoe on my JD 310D the front loader arms will leak down (or up actually) and if I keep digging 10 more minutes the loader bucket will actually raise off the ground. Machine has 8,500 hours. No external leaks at the control valve. Any one have experience with this problem?
Sounds like a worn spool or the bore in the valve body, or a hairline crack in the valve body, or the spool not centering due to a broken or weak centering spring or linkage sticking or out of adjustment.
I removed and disassembled the loader control valve. I found 1 o-ring completely destroyed (photo shown) and two others damaged. They are all internal o-rings on check or release valves. I'm replacing all o-rings. I'll let you know how it works after the fix. The actual symptoms are the loader boom rises and the loader bucket curls up while the hoe is being used but nothing happens while the hoe is not used.
Very interesting Deon, I hope that fixes your problem. Very typical of o-rings, heat and age makes them get hard as a rock, that's when they begin to break apart. Bad part is the condition of those o-rings are an indicator of the condition other o-rings are on the machine. Nothing you could have done to avoid it, just a result of time. Keep us updated.
Willie59, Yes I agree. The nice thing is that all the check valves, poppets & spools look like new. I know that if this work out, I will be replacing all o-rings on the backhoe control if it starts acting up. I really enjoy this old machine but it's much more fun when all works the way it's suppose to. I've got one other issue I haven't yet resolved. Maybe you can help me with. My brake pedals are high and firm in the morning. Once the machine is warmed up the pedal usually needs to be pumped once to bring the pedals up. Once the pedal is up the pressure seams to stay while I keep my foot on the pedal. If I release it I need to pump once again to bring it up. The adjustment at the brake disk on the 3 cap screws are as per the manual, just 1/3 of a turn slack.
I do declare, not certain what would cause that problem. I don't know a whole bunch about the 310, but I'm near certain that Deere machines like that get brake pressure from the hyd system, not a brake fluid reservoir system, so they have an unusual master cylinder setup. Have you tried bleeding the brake system to see if that helps?
Got it. Replaced each and every o-ring and the spool dust seals and now the loader stays where I put it. I took the opportunity to drain the hydraulic tank and have a look at the pickup screen. It was clean as a whistle but I rinced it in varsol anyway and blew it dry. Now I feel it works like new. Best part is all the parts cost a total of $20.00.