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Discussion Starter #1
Ok so i have a Yanmar 336D with a front end loader. The spool valve was worn out and some parts were broken or missing so i replaced it with a new one. This problem happened with the old spool valve as well so i dont think its the valve itself. Basically unless the 3 point is raised to its maximum height to the point where you can hear a change in engine tone the loader will not work! When i max out the 3 point i can see the input hose going into the loader spool valve pressurize and the RPM drops a little even when im not controlling the loader. If i lower the 3 point just a little bit the engine goes to normal idle but the loader has no pressure and the bucket will just drop no matter what position you move the control lever in just as if the machine was turned off. Please help! i really want to get this fixed. The bucket also seems to go very slow but right now that's the least of my worries! :dunno:

Thanks
 

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It's plumbed incorrectly.

Hydraulic valves are plumbed in series when the circuit is open centered. In one valve set, out of that set and into the next set, and out of that one and back to tank. You have a T in front of the valves and are trying to feed both at the same time. That only works if one valve is stopping oil flow (your 3PH with the valve in the UP position) so that the oil is forced to go through the loader valves.

Lose the T and plumb as above. You also need a power beyond kit for the first valve set in the series unless there is a relief valve at the pump.
 

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Discussion Starter #3
I have a power beyond kit installed and there is an adjustable relief valve on the spool. There is 3 lines hooked to the spool other than the lines for the bucket and boom but it was like that from the factory. There is not a T connector or anything on it, just 3 ports other than the loader control ones.
 

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Where does the fluid come from?
 

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Which valve block is first the 3PH or the FEL? Is the 3PH a position control type, or just a lever that returns to center when you find position? Can you separate the two systems?
 

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Discussion Starter #6
Which valve block is first the 3PH or the FEL? Is the 3PH a position control type, or just a lever that returns to center when you find position? Can you separate the two systems?
Im pretty sure the 3 point is first, it looks like the pressure line runs form the pump into a block with a switch you can adjust for faster or slower operation of the hydraulics and then lines come out of it to the loader. As far as the 3 point i am not 100% sure, its just a lever with no markings on it that you raise or lower and it holds that position.
 

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Im pretty sure the 3 point is first, it looks like the pressure line runs form the pump into a block with a switch you can adjust for faster or slower operation of the hydraulics and then lines come out of it to the loader. As far as the 3 point i am not 100% sure, its just a lever with no markings on it that you raise or lower and it holds that position.
There's the "T".

Which lines go where from that block? Hopefully it has designators cast into it beside the ports. Does it have a tag with a manufacturer, or at least a part number cast into it?
 

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Discussion Starter #8
There's the "T".

Which lines go where from that block? Hopefully it has designators cast into it beside the ports. Does it have a tag with a manufacturer, or at least a part number cast into it?
I took some photos today, hope they help. I think both lines are going into the spool valve from the block, i forgot to look before i left this morning.

IMG_20130516_093705.jpg

IMG_20130516_093712.jpg

IMG_20130516_093719.jpg

IMG_20130516_093750.jpg
 

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The ports on the valve are lined up in 2 rows across the valve. One row has 5 ports, including the ones on either side. From left to right in the pic:

1. Power beyond.
2. Return line.
3. Work port 2-A.
4. Work port 1-A.
5. Supply line.

Where are the other ends of the hoses at 1, 2, and 5?

Where they should be is:

1. The 3PH valve.
2. The reservoir, or a T at one of these; the reservoir, the pump inlet, the return line from the 3PH valve.
5. Pump outlet.

I can't find any information from that tag other than it might be the pump. If the small lever is in fact on the pump, it may be a variable displacement vane pump. Of this, I am unsure without confirming data, and may be totally wrong with the sparse data available.

The lever may also be on a flow control valve, which brings to mind:

- Where is its source of fluid?
- Where does the fluid go?
 

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Discussion Starter #10
The ports on the valve are lined up in 2 rows across the valve. One row has 5 ports, including the ones on either side. From left to right in the pic:

1. Power beyond.
2. Return line.
3. Work port 2-A.
4. Work port 1-A.
5. Supply line.

Where are the other ends of the hoses at 1, 2, and 5?

Where they should be is:

1. The 3PH valve.
2. The reservoir, or a T at one of these; the reservoir, the pump inlet, the return line from the 3PH valve.
5. Pump outlet.

I can't find any information from that tag other than it might be the pump. If the small lever is in fact on the pump, it may be a variable displacement vane pump. Of this, I am unsure without confirming data, and may be totally wrong with the sparse data available.

The lever may also be on a flow control valve, which brings to mind:

- Where is its source of fluid?
- Where does the fluid go?
I know the reservoir line just goes straight into the trans-axle housing. The supply line and power beyond im pretty sure just go into that block at the rear. That block is not the pump, the pump is at the front and has 2 hard steel lines going to it and back to that block assembly. Is it possible the supply line and power beyond lines need to be switched? Would that cause this issue?
 

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Discussion Starter #11
Ok, took a few more pics. Both the Power Beyond and feed lines go into that block bolted to the 3 point hitch cylinder assembly. I labeled one of the photos, hopefully it will help. In the second photo i have some sort of handle you can turn to thread in and out, what is this? Third photo is just of where the out line goes from the spool valve into the trans axle housing. fourth is just another photo of that block/valve assembly again.
mtfhydopic1.jpg
IMG_20130516_183538.jpg
IMG_20130516_183548.jpg
IMG_20130516_183123.jpg
 

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Did you ever try to navigate from one city to another in an area that you are totally unfamiliar with by using only the individual city maps on the back of the state highway map? It doesn't work. You need to see the state map to find the relationship between the 2 cities and other intervening complexities.

Pull back with the camera for a broader picture showing the relationship between the 3PH valve, that unknown block, and an easily recognizeable portion of the tractor, preferrably including either the pump or the loader valve set, or at least a good portion of the lines involved.

The round knob is, I believe from my tractor, a rate of drop control and lockout for the 3PH cylinder. Raise the 3PH and close that valve partially and lower the 3PH and it will lower slower than normal. Close it completely and the 3PH stays up no matter what you do with the control valve lever for it. Speaking of which, is that the lever beside the unknown block in picture #2?

Again from picture #2, is the steel line curving around the lockout valve the supply line direct from the pump? How does the fluid get to the unknown block so that it can get to the loader valve set?

Gotta figure out the purpose of that unknown block! Any suggestions?
 

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This is a positional 3PH, just like the big tractor. I drove Ag tractors with loaders and 3PH in my youth but can't what you did when changing from one to the other. I thinks Bob's on to something; lift the 3PH, lock it in postion the that knob, and then try your FEL.
 

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Discussion Starter #14
Pull back with the camera for a broader picture showing the relationship between the 3PH valve, that unknown block, and an easily recognizeable portion of the tractor, preferrably including either the pump or the loader valve set, or at least a good portion of the lines involved.

The round knob is, I believe from my tractor, a rate of drop control and lockout for the 3PH cylinder. Raise the 3PH and close that valve partially and lower the 3PH and it will lower slower than normal. Close it completely and the 3PH stays up no matter what you do with the control valve lever for it. Speaking of which, is that the lever beside the unknown block in picture #2?

Again from picture #2, is the steel line curving around the lockout valve the supply line direct from the pump? How does the fluid get to the unknown block so that it can get to the loader valve set?

Gotta figure out the purpose of that unknown block! Any suggestions?
Ok so i took some more photos, the tractor has a very tight operator station so its difficult to see everything in the photos. The block is bolted directly to the 3 point so it may very well just be part of it. Also if you click this PDF link and start at figure 73 you will see a breakdown of the hydraulic system on a few of the pages. I did not get to try closing the lockout valve yet, i will try today.

http://downloads.pfgaustralia.com.au/intranetwebcache/Parts/Parts Manuals/Yanmar/Y00T2140.pdf

IMG_20130518_100010.jpg

IMG_20130518_100028.jpg

IMG_20130518_100045.jpg

IMG_20130518_100052.jpg


Thanks for all your help so far! I am hoping to have the tractor ready by next week as i have A LOT of brush to move!
 

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Much better! Thank you. The PDF helped a lot, too. It remains to be seen how much it helped.

The "unknown block" is the 3PH control valve. The plumbing is the source of your problem. What to do about it, I'm not certain without knowing the circuitry inside of the darned thing.

The parts diagram 42 (page 73) does not coincide with the pics of your tractor. The shifter housing is turned 180* and the case regulator, which includes a relief valve is nowhere to be seen in your pics, but the diagram indicates that it should be in the same location as the 3PH cylinder housing and control valve. Confusing!

In any event, that round control handle in front of the cylinder housing is a shut-off for the cylinder proper. Close it and oil can neither enter nor leave the cylinder. The small lever on top of the control valve controls the rate of return for the cylinder.

Since reversing the order of flow to where the loader is first in the circuit is a non-runner due to specialized fittings on the 3PH control valve and a lack of specific circuit information in the 3PH control valve, we're reduced to experimentation. The "T" connection that I referred to earlier, is in that valve and needs to be changed to a flow through connection.

The power beyond line from the loader valve is redundant. Either connect it with a "T" to the return line to dump back to tank, or remove the power beyond fitting and plug the port. At the 3PH end, plug the port that was used by the power beyond line as a first attempt at making it work correctly. I don't think that it will change the situation, but I don't want top make more than one change at a time.

I have a sneaking suspicion that you will have to find a power beyond kit for the 3PH valve and install it in the port currently occupied by the power beyond line from the loader valve set and move the loader supply line to that port and plug the port that it currently occupies. But, I can't prove it.

The current flow path is from the pump to the 3PH open center valve and directly to tank when that valve is centered. When that valve is in the lift position and the hitch is lifted all the way, the oil normally goes over the relief causing the reduction in rpm that you currently experience, and allowing oil to flow to the loader as the path of least resistance..... I have several scenarios running through my head right now, and the one that I just typed isn't making hydraulic sense. I'm missing something...

I'm going to let the hind brain chew on this for a while. I'll get back to you later.
 

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If this was my tractor I would do what it takes to put the loader control first and use the power beyond to the 3ph (cut the steel line, insert hose with QD's; so you bypass loader valve if you take loader off tractor). This may not be the original way the circuit worked but would be better. The loader was an add-on and the OEM worked with what they had.

Ask your question at the big boys section and see what they say.
 

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I agree with both suggestions. I was trying hard to keep the original configuration, but can't figure out how without that little bit more information about the valve circuitry.

I will make one more suggestion. Disconnect the supply and power beyond hoses at the loader valve set and put the ends in a clean bucket. With the 3PH valve in the center position, start the engine at idle and observe which, if either, hose flows oil.

That one will be your supply hose and the other is redundant. Take it out of service as I suggested earlier, including removal of the power beyond plug from the loader valve set.

If that doesn't work, either cut the line from the pump and make the loader first in the circuit or take it to the big boys forum, as Hydronerd suggested
 

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Discussion Starter #18
Sorry guys i have been so busy lately! I want to thank you all for the great help and insight..... The one thing about the tractor that completely baffles me is the fact that the loader is a factory loader and came with the tractor when it was purchased new. The factory spool valve that was on it had 7 lines connected to it..... i think i need to find someone with the same machine that can send me pictures or something. Thanks again guys i will let you all know what i did when (if) i figure it out finally!
 

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The correct number of lines on the loader valve set is 7... if the loader is first in line for fluid from the pump. Othewise, it is 6.

Someone has done some replumbing to put the 3PH first in line for fluid.
 

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Any news? I noticed there's a Yamar heading under the CUT section.


... The one thing about the tractor that completely baffles me is the fact that the loader is a factory loader and came with the tractor when it was purchased new...
They likely designed the tractor first with just the 3ph, then designed the FEL as an option and didn't want different hydraulics on machines with the FEL (except the hyd's needed for fel).
 
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