Have L39 and use it to operate a soil sampling tool on the front quick connect that has a hydraulic cylinder and hydraulic hammer to push/hammer the soil probe into the ground. I plug the hydraulic hoses in series with the return from the backhoe to power the probe. When in use I put down the stabilizers to provide a stable platform. On my last job the stabilizer controls started to leak and they got hard to operate. I would push the lever up to raise the stabilizers and it was real hard to push and sluggish to operate. If I worked it a couple of times it would work like normal. Had the same problem with both stabilizers. It was like pressure was building up behind the plunger valve making it hard to operate until I moved it a couple of times and then was ok. Any ideas on whats going on? Its leaking out the top of the valve piston so I am thinking an oring or something. Just doesn't make sense that its happening on both sides.
Backhoe stabilizer problem
- Thread starter sgrol
- Start date
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Farmerford
Platinum Member
- Joined
- Dec 9, 2006
- Messages
- 733
- Location
- Columbus, Georgia
- Tractor
- Kuborta B2400, L2900, L4330; Caterpillar D3B, John Deere 455D
I suspect the backhoe valves are not designed for substantial pressure in the "out" or "tank" circuit; that is, they do not have a power beyond circuit. When you shift the valve you added for the front-end tools it creates pressure in the backhoe valve tank circuit, which is usually sealed from leaking by o-rings around the ends of each spool. The stabilizer valves are leaking because the o-rings are not designed to seal agains full system pressure (which is what occurs in the backhoe tank circuit when you fully shift the front valve and then stall the tool). The stabilizer spools are "sticky" because the pressure has extruded the o-rings partially out of the o-ring grooves and probably damaged them in the process.
The mystery is why the other backhoe valves (swing, boom, stick, bucket) are not having the same problem. That suggests my analysis may be wrong, but I can't think of another reason for the problems you are experiencing.
One solution is to move the connection for the front valves from the backhoe "out" circuit to the front end loader "out" circuit; the FEL valve should be a power beyond valve that is designed to be upstream of another valve (the backhoe valve), while the backhoe valve is not so designed.
Let us know what you find out.
The mystery is why the other backhoe valves (swing, boom, stick, bucket) are not having the same problem. That suggests my analysis may be wrong, but I can't think of another reason for the problems you are experiencing.
One solution is to move the connection for the front valves from the backhoe "out" circuit to the front end loader "out" circuit; the FEL valve should be a power beyond valve that is designed to be upstream of another valve (the backhoe valve), while the backhoe valve is not so designed.
Let us know what you find out.
Removed the upper sealing oring on one of the stabilizer piston valves (just under the wiper seal). It was split circumferentially. That would explain the leaking out the top. I suspect, and will check tomorrow, that the lower oring is also faulty allowing fluid under the piston and making it hard to push in since pressure would be on the under side. I had also suspected that there was more fluid leakage on the bottom of the valve than the top. Stay tuned...
Stonehaller
Platinum Member
You will have problems with how you have connected your soil sampler. You should install a selector valve on the high pressure side so you can feed either the back hoe or the soil sampler. You can tee in the sampler return to the back hoe return. You could use a simple manual selector valve like this
Surplus Center - SAE 16 40 GPM SINGLE SELECTOR VALVE CROSS VS4BKLF9
Or 12 volt operated valve like this one:
Surplus Center - SAE 12 15 GPM 12 VDC HYDRA FORCE SELECTOR VALVE
Make sure whatever value you use is rated at least 11 GPM and 2750 psi, which is the rated flow and relief pressure for the main pump on the L39.
Surplus Center - SAE 16 40 GPM SINGLE SELECTOR VALVE CROSS VS4BKLF9
Or 12 volt operated valve like this one:
Surplus Center - SAE 12 15 GPM 12 VDC HYDRA FORCE SELECTOR VALVE
Make sure whatever value you use is rated at least 11 GPM and 2750 psi, which is the rated flow and relief pressure for the main pump on the L39.
Stonehaller
Platinum Member
As a further note, the return line on the backhoe handles flow from both the main hydraulic pump and the swing pump. So at 2700 RPM there will be 11 + 6.2 = 17.2 GPM in the return line. If you connect your sampler to just the main hydraulic pump like I suggested, then your sampler will only get 11 GPM. But again, you cannot connect in series on the return line without damaging the seals in the backhoe.
Thanks for the replies guys. I replaced about 6 or seven damaged orings in stabilizer and backhoe circuits. After reading the replies, I now understand the problem. When I operate my hammer (or bottom out the cylinder) there is 1500+ psi of backpressure on the backhoe valves. Looks like the pressure has taken a toll on the orings. I like to have max flow since I'm pushing a 4" cylinder up and down and the more flow the faster it operates. So hooking into the return downstream of the backhoe takes advantage of having both pump's flow. Plus, I still have operation of stabilizers that I use to transfer tractor weight to front. I believe I will upgrade to viton orings. If that doesnt work, I may have to go with the selector valves or t into the frontloader circuit. Just don't know the pump flow for the front end. I suspect it is the same pump as the backhoe operation pump (without the added flow of the swing pump).
Stonehaller
Platinum Member
I don't think viton seals will help. The valves are just not designed to have that much pressure on the tank line.
The main pump (11 gpm) powers the loader and power beyond from the loader goes to the backhoe or 3 point lift. If you really need more than 11 gpm, you could combine both the swing pump and main pump on the pressure side but you should have check valves, at least in the swing pump line to prevent the main pump from back feeding it. The swing pump relief is 2500 psi which is lower than the main pump so you should have an additional relief set lower, maybe 2000 psi after you combine the two. Maybe your sampler already has a relief built into it since you mention it runs at 1500 psi. If that is the case then you probably do not need another relief.
So to make this work, you would need a selector valve to switch the main pump flow that feeds the backhoe between the hoe and the sampler. You could probably just disconnect the swing pump line from the hoe, since you are not using the hoe, and connect a line from the swing pump connection on the back of the tractor, through a check valve, to the pressure circuit after the selector valve that feeds the sampler. Tee the return line from the sampler and additional relief if you add one to the return line from the hoe. Note that when the selector valve is set to feed the hoe so you can use the stabilizers, the swing pump is still powering the sampler so you could move it simultaneously (but much slower) with the stabilizers if you need for setup. Once you are setup, switch the selector valve to feed the sampler and you get flow from both pumps.
The main pump (11 gpm) powers the loader and power beyond from the loader goes to the backhoe or 3 point lift. If you really need more than 11 gpm, you could combine both the swing pump and main pump on the pressure side but you should have check valves, at least in the swing pump line to prevent the main pump from back feeding it. The swing pump relief is 2500 psi which is lower than the main pump so you should have an additional relief set lower, maybe 2000 psi after you combine the two. Maybe your sampler already has a relief built into it since you mention it runs at 1500 psi. If that is the case then you probably do not need another relief.
So to make this work, you would need a selector valve to switch the main pump flow that feeds the backhoe between the hoe and the sampler. You could probably just disconnect the swing pump line from the hoe, since you are not using the hoe, and connect a line from the swing pump connection on the back of the tractor, through a check valve, to the pressure circuit after the selector valve that feeds the sampler. Tee the return line from the sampler and additional relief if you add one to the return line from the hoe. Note that when the selector valve is set to feed the hoe so you can use the stabilizers, the swing pump is still powering the sampler so you could move it simultaneously (but much slower) with the stabilizers if you need for setup. Once you are setup, switch the selector valve to feed the sampler and you get flow from both pumps.
