Boomer 8N Loader won't lift unless bucket is curled back

[LD1]

Sounds like you have cylinder seals blown out or a broken rod. Just fixed the same issue with a 310j backhoe, Running both sides of the hydraulics will increase flow in the system and overpower the fault momentarily. The best way to test is to set the rods at mid travel, hold them up with heavy jacks/another machine, tree stumps, etc (any way you can do it safely). cap the lines to the cylinders and remove whatever is holding it. You will get some initial drop of a couple inches from introducing some air into the system but it should hold stead after that initial drop. If it falls completely you will need to have the cylinders re-packed at a minimum.

Bad advise, and incorrect information for testing loader seals.

It looks like some of you guys know your hydraulic a lot better than I do. To quickly address some of the questions, it has 129 hours on the tractor. The loader was purchased with the tractor when new and is the special red 250TL that was painted red and stickered to match the tractor. I don't think it was used or anything like that. It is an 09 but I bought it from a dealer 3 years ago with 12 hours and that had to be the last one anywhere that hadn't sold. I hadn't used the lift too hard until I had a hole dug for a basement pour that made a huge pile of clay that needed moved after they were done. Until a couple weeks ago when I replaced the leaking hose, I had never disconnected the quick connects and last night was the first time I have ever removed the loader from the tractor. Pressure gauge finally came in and I went to tractor supply and picked up some fittings to get some readings. 2500 PSI at all quick connectors when circuit was activated. So I probably didn't have it set up correctly because next I put a "T" fitting on for checking pressure along the different points. As soon as I put a T in the line, the pressure reads about 300-400 psi. This is the first clue on what is going on. Anyways, After messing around with it and "checking pressure" at several points, I took off the line and put the gauge on the end of the hose supplying the right cylinder (I was curious if hydraulic hoses swell up and pinch off supply like a rubber brake line does) like and so the gauge terminated the lift line (plugged it off) so I could get a pressure reading. I guess they don't but I was stumped and looking at everything I could think of. When I started it up that time, I pulled back on the joystick and the loader lifted up (with great surprise I might add) with just the left side cylinder connected. Anyways, I pulled the loader off to get to the cylinder attachment points and removed that lift cylinder. There is something inside rattling around so I am guessing that something let loose and that is where the problem lies. I don't have another day off until next week so I'm taking the cylinder to the New Holland dealer and they are going to check it out for me. So, discussing it with a friend, why would it still lift when you had it curled all the way back and the best guess and our conclusion is: no clue, but maybe since both are draining, it caused some pressure to build up allowing the other cylinder to do the lifting. Pure speculation. But I now know that there is a problem in the right lift cylinder and things make a little more sense.

Late to the thread, but it sounds like you have a broken piston, or at least a nut that has fallen off the bottom of the piston that holds that rod on.

Why your curl was having an influence on the loader lift....yea thats odd.

Waiting to see what you find inside that cylinder.

 

[cougarmandan]

Cylinder is toast is what I am told. They just said the rod separated from the piston is what they said. The piston is stuck inside, the walls are scored beyond use from the rod scraping them and it "looks brutal inside". So they have ordered a new one. I personally think the nut came off the shaft allowing it to slide out and in of the piston hole allow it to fill and that explains the having to go all the way down to put the rod in the hole before it would go up. The curl thing is super confusing. The best I can figure is that the curl would overwhelm the to tank flow causing to drain slower and pressure to build up on the good side but just a guess. I'll pick it up sometime this week and have it in my hands.

 

[oldnslo]

Hopefully the attached valve schematic will help explain what was happening with your FEL. This is based on having a directional control valve with the series circuit like what is used on some Kubotas.

 

[PJ The Kid]

LD1 what do you recommend for testing internal seals? That is how I have always done it, and how I learned from other heavy equipment mechanics. It checks to see if the seals are bypassing. I will admit, I had one that the nut had come loose from the rod and let the piston come off, that would work fine inder pressure, but as soon as the valve was neutralized it would drop.

 

[LD1]

LD1 what do you recommend for testing internal seals? That is how I have always done it, and how I learned from other heavy equipment mechanics. It checks to see if the seals are bypassing. I will admit, I had one that the nut had come loose from the rod and let the piston come off, that would work fine inder pressure, but as soon as the valve was neutralized it would drop.

A loader WILL NOT drift if seals are bad. You CANNOT compress a hydraulic cylinder even if the seals were completely removed.

Note: this does not apply if the cylinder drift is EXTENDING the cylinder. Like a bucket drifting open and pulling on the cylinders.

There are a few ways you can test, and all require a certain level of safety because pressurized fluid and suspended loads via hydraulics are inherently dangerous.

One way would be: With the loader elevated some, take a wrench and loosen or remove the ROD side fittings. IF the seals are good, minimal oil should come out. Sure a few drops will come out due to residual pressure and oil in the line. IF the seals are shot, Oil will bypass them seals and come out that rod port while the loader simultaneously starts to drift down.

Another way can be done on or off the tractor. Fully extend the cylinder. (if done on the tractor this will raise the loader ALL the way). Now remove the rod side hose again. Now try to raise the loader MORE. The loader wont actually raise since its full up (or cylinder fully extended). But what you are doing is putting full pressure behind the piston. If the seals leak by, oil will come out rod port. Its important you start with the cylinder FULLY extended for this test. Because if you dont, when you do this test the cylinder WILL fully extend and all that oil that "was" on the rod side will be purged out and make a mess.

This is basic hydraulics. And its astonishing the number of people that dont understand. OR the number of times I hear someone blaming cylinder seals even when they have no bearing on the problem. Some get the concept, some dont.

 

[PJ The Kid]

So you're saying that blown piston seals will not let the fluid bypass the piston and allow movement. It is not compressing, it is bypassing. I recently repaired a crane that with both the up and down sides blocked off it would let the crane fall under its own weight, re-packed and it worked perfectly and would hold with both sides capped off. Think of a syringe. with the seal plug installed put your finger over the end and try to move the plunger. You may get some flex (mostly due to materials) but it will not move. Now cut a slice in the plunger and try the same thing.

 

[100 td]

A loader WILL NOT drift if seals are bad. You CANNOT compress a hydraulic cylinder even if the seals were completely removed.

Sorry, you can extend and/or retract a cylinder if the seals are bad. If the seals are perfect and no fluid can bypass, then you can not.(If the valve is perfect or the cylinder is capped)

 

[100 td]

This is basic hydraulics. And its astonishing the number of people that dont understand. .... Some get the concept, some dont.

You nailed it!
EDIT: So did PJ

 

[LD1]

No, you cannot retract a cylinder if the seals are bad. Period. Those that claim you can, do NOT understand basic hydraulics.

Extension is different.

 

[oldnslo]

No, you cannot retract a cylinder if the seals are bad. Period. Those that claim you can, do NOT understand basic hydraulics.

Extension is different.

To expand on what LD1 is saying the following criteria must be met.
1) The cylinder must be a single rod cylinder.
2) Both ends of the cylinder must be full of oil.
3) There is no external leakage path from the cylinder.

If these conditions are met then you can NOT retract this cylinder even with no seals on the piston. (NOTE: The cylinder will move slightly due to the oil compressing slightly.) The reason for this is the difference is the difference is volumetric area of the cylinder.

Example using a 3" bore 1 1/2" rod 18 inch stroke cylinder

3" bore x 18" stroke = 127.23 cubic inches volume cap end of the cylinder

1 1/2" diameter rod 18" long = 31. 8 cubic inches. rod volume

127.23 - 31. 8 = 95.43 cubic inches Rod end volume. You can NOT fit 127 cubic inches of oil into 95 .4 cubic inch space.

Like LD1 states: you can extend this cylinder since the smaller rod end volume will fit into the larger cap end volume.