Go Bottom226d Hydr Problem
 | DaveA
Join Date: Posts: 1 
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2004-04-04 82104
1987 226d w/Yanmar bucket loader. Loader wont operate unless there is a load on the 3pt hitch. If the load on the 3pt hitch is released, the bucket stays in position..until you operate the control lever, then it just drops slowly.
Any suggestions on how to narrow the problem down before I bring it to someone else to fix it?
Thanks
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley 
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2004-04-04 82130
I'm guessing that the loader only lifts when the 3ph is in lift mode and with a fairly heavy than is in the loader. I wondering if it has always done that or it's a recent problem and if the bucket cult is affected?
If so it sounds like a parallel hookup in the high-pressure line, which creates a condition where the both loads will move but the lightest moves first. A hookup to the loader with a t-fitting in the high-pressure line would do that. A blown diverter valve or one in mid-position (if the tractor has one) as well as various failures in the loader valve are possibilities. ....
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| daveaa
Join Date: Apr 2004 Posts: 3 Henniker NH
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2004-04-06 82341
I'm guessing the main or safety relief valve ar hung up? Does that make sense? ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2004-04-07 82370
Yes a relief-valve makes some sense but more info is needed from Dave to sort it out.
The key is that the loader only lifts when a load is on the 3ph, and I'm assuming that's only when the 3ph is in lift mode. If the loader valve has a single return port then oil from a relief high-pressure line in the loader valve would go into the return line and on to the 3ph. If the 3ph is in neutral or lower the oil simply goes to the reservoir. However, the return is blocked when the 3ph is in lift mode which would hook up the lift and loader cylinders in series and the 3ph would lift unless its weight exceeded the loader.
The system relief and loader PB valves that have two return lines have independent returns to the reservoir so that wouldn't happen. Another possibility is that the loader valve isn't PB rated was operated at the same time as the 3ph was in lift and carrying a heavy load. That can ruin a loader valve. ....
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| daveaa
Join Date: Apr 2004 Posts: 3 Henniker NH
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2004-04-09 82582
Tom is right...the loader only lifts when the 3pth is lifting w/ a heavy load. Without a load on the 3pth, the loader doesn't work even when the 3pth is lifting. So, does that mean it's the loader valve? Is there a way to check? ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2004-04-10 82619
Morning Dave. I did write 'series' when I meant 'parallel.' Sorry if that confused the explanation for you or anybody else. This is too long but I don't know how to make it much shorter.
If the tractor has always done this since you've had it there is the possibility of a wrong hook-up. The hook-up would be about the only thing easy to check out.
I think I recall that these tractors do not have a manifold block for auxiliary hookups such as loaders. When people add loaders they usually splice fittings into the high-pressure line that runs to the 3ph. A t-fitting in the high-pressure line where one leg goes to the loader and the other to the 3ph would operate as you describe.
Old farm tractors before power-beyond hydraulics had this type hook-up but used a diverter valve rather than a t-fitting. That gives a choice between 3ph only or loader only operation. A diverter valve that was in the centre may leave both legs partially open and that would be the easy fix.
I'd trace the line from the pump. If you find a block then it has a diverter valve that likely has a slot screw head on its face. That's the valve control and it should be fully one way or the other. If the line goes to a t-fitting then the hook-up needs to be redone. If the line goes to the loader valve inlet and the outlet continues on to the 3ph then the problem is likely the loader valve.
A standard hook-up for the open centered system on the tractor is to have the loader valve in series and ahead of the 3ph. That is called a power-beyond application and the valve is supposed to be power-beyond rated. A single return port valve may or may not be PB rated and that may be the problem. A valve that isn't PB rated used in this type setup is risky and should be replaced whether it caused the immediate problem or not.
A hydraulics shop should be able to identify the valve and know if it's appropriate for the application, and if it's broken know if it can be rebuild or needs replacing. ....
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| daveaa
Join Date: Apr 2004 Posts: 3 Henniker NH
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2004-04-10 82660
Thanks Tom... This is a new problem.. No t line, the pump has an auxillary port for the loader valve....your explaination leadds me to belive it is the laoder valve. I'll remove that and bring to the hydraulic shop.Thanks for the help and I'll let you know the final fix!
DaveAA ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2004-04-11 82709
The loader valve seems a good bet but I'm not certain it's a sure bet. If it comes to replacing the valve a PB valve assembly with a float feature on one valve would be standard. There are a few more features available that might be of interest. First might be an extra control valve section for a rear outlet. A control valve with a regenerative feature for fast dump also might good. There are a few other features a shop would know about.
I'm still curious about the hook-up. I haven't heard of a pump itself that has two outlets although that doesn't mean much. There's no reason why a diverter or other valve couldn't be built onto the pump body. My Ford pump does have a priority valve that runs the power steering built onto the pump and that may seem like a second outlet. There's almost certainly something more than just a second outlet.
A second curiosity is whether the loader valve has one or two outlet lines? If it has two it's a PB valve and one line likely runs directly to the cases. The other would return somehow to the high-pressure line that feeds the 3ph. I'm curious where the second line or a single return line goes.
Another part of your description is that the loader lowers slowly. I wonder if it lifts slowly and the bucket also is affected. Slow lowering could result from damage to the valve that partially obstructs the return side of the lower circuit (assuming that it has double acting cyinders). It could also result from an obstructed feed to the loader from this 'auxiliary port' that likely has valving that hasn't been identified.
It's important to know if a relief valve squeal is present. There also are some simple checks that could be done such as reversing the cylinder lines on the lift valve and swapping the bucket and lift cylinder lines. I'm not sure the info would be of much value to you though. ....
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