Yanmar YM336D Slow Loader - Pressure Relief or Bad Cylinders or ?

[jsdepottey]

I searched and couldn't find anything relating to this so I apologize if I missed it. My loader moves so slow that it's getting on my nerves!! It takes 23 seconds to raise from the ground to full boom lift position. I installed a gauge to see what the pressure was during the cycle. Pressure rises to 500 psi on the rise until full up position - SLOW. When I reach full up position the pressure slowly rises and reaches ~2100 psi. According the manual that's within the main pressure relief valve. When moving the boom down, the pressure relief starts screaming a little over 500 psi and seems to slow the down speed too. It takes a approximately 13 seconds to lower.

Since I've had the tractor the loader has been SLOW. The loader valve was broken when I got the tractor so the loader would drift all the time. I got a great deal on a replacement so I changed it. No improvement. The tubing on the loader was smashed pretty bad so I thought that it could be restricting the flow so I replaced the tubing with hoses. No improvement. I've read multiple people having problems with QD. I have removed them from the boom circuit. No improvement. I've changed the hydraulic fluid, cleaned the sump screen and eliminated the filter on the suction side of the pump. No improvement.

Any advice? Thanks in advance.

 

[J_J]

Have you done any test to see if the cyl and valve are good?

The speed of a hyd component is directly related to GPM's, so if the pump is working and the cyl are good, there appears to be a restriction in the flow path.

Have you tried new hoses between the cyl and valve.

Are you sure there are no restrictor fittings. Some people install them by mistake.

Do you know the pump rated GPM capacity?

Have you disconnected a cyl hose and determined if the valve is passing the pump flow.

A flow problem could be any number of things. Pump weak, crushed hose or tube, restrictors installed, return path fowled. Should be no or very little back pressure on the return line.

Could your 3pt lever be in the raised position causing the relief valve to operate?

A hyd shop can do a flow and pressure check.

Are your hyd components matched for GPM's? You know, pump, hoses, valves, etc.

Using your know pump GPM, have you figured the cyl cycle time?

 

[jsdepottey]

Thanks for the suggestions. Responses added below.

Have you done any test to see if the cyl and valve are good?

The speed of a hyd component is directly related to GPM's, so if the pump is working and the cyl are good, there appears to be a restriction in the flow path.

Have you tried new hoses between the cyl and valve.
The valve and hoses are new 3/8".

Are you sure there are no restrictor fittings. Some people install them by mistake.
I have not replaced the tubing from the hydraulic pump to the splitter valve by that appear to be factory installed.

Do you know the pump rated GPM capacity?
Its basically a JD 1050 Tractor somewhere in the 8-10 GPM?

Have you disconnected a cyl hose and determined if the valve is passing the pump flow
Not sure what you mean here. I have not measured the GPM from one of the hoses. I was worrying about starving the pump..

A flow problem could be any number of things. Pump weak, crushed hose or tube, restrictors installed, return path fowled. Should be no or very little back pressure on the return line.
I can see the return from the loader valve and it appears to be an in restricted flow coming back when lowering the boom. I have not replaced the return hose but its oversized and has good flow.

Could your 3pt lever be in the raised position causing the relief valve to operate?
I don't think so. When not operating the loader the pressure on the gauge is very low.

A hyd shop can do a flow and pressure check.
I may have to resort to this but I don't have a trailer to take it there. Have to borrow one.

Are your hyd components matched for GPM's? You know, pump, hoses, valves, etc.
I think they are. The 3/8 hose and loader valve should be more than capable of taking the flow rate.

Using your know pump GPM, have you figured the cyl cycle time?

No but a JD 1050 with a loader says it should have 4-5 second cycle time. I would take 10 seconds compared to my current 23.

 

[jsdepottey]

Here's a copy of the hydraulic circuit from the manual.View attachment YM336 hydraulics with loader.pdf.
Could it be the lowering valve (Q)?

 

[rScotty]

The YM336 is related to the JD1050, but is generally more sophisticated. The 1050 seems more related to the older gear-type YM330. The YM336 uses a proportioning valve to divide the hydraulic flow between the various circuits. Not my favorite way to dispense flow; I think they were looking for fuel efficiency and it does do that.
YM336 power steering is internal and designed so that the power steering circuit always gets priority. That's where I'd look first - at the proportioning valve. I think it is adjustable. That's after double-checking that the loader control valve isn't wrongly set up for a closed circuit hydraulic system.
When you have proportioned branch circuits like these one does you can't rely on psi alone because flow is what does the work. Diagnosis is always a wierdo on parallel circuits anyway.... and inserting flowmeters into each circuit is too expensive to contemplate.
I'd check the proportioning valve and then see if actuating the power steering farther slows the loader....get some clues as to where the flow is going. Then try to watch psi on several circuits at once.
luck, rScotty

 

[J_J]

I believe you have a restriction in your lift hoses. whether it is a QD or a restrictor fitting.

How fast is your bucket curl?

Try switching hoses from lift to curl and see if there is any difference.

Your relief valve should not scream on the retract stroke until you have fully retracted the cyl.

 

[jsdepottey]

Thanks rScotty. The manual tells me how to adjust the pressure relief on the priority valve for the power steering but I didn't see how to adjust the flow yet. I'll keep digging to see if there is an adjustment. Jim

 

[jsdepottey]

J_J The problem existed with my old loader valve and smashed hydraulic lines to my cylinders. I have replaced the loader valve because it was broken and drifted. At that time, I also replace the smashed hydraulic lines with brand new hoses and fittings all the way to the cylinders. That didn't solve the problem either. I removed the QD's from the lift cylinder circuit too just to remove another variable and stilled didn't solve it.

My bucket curl probably takes 3-4 seconds, I haven't timed that one. The cylinder are much smaller and shorter stroke so it doesn't seem as bad. How much time should it take? I can't remember if I have the same problem with the curl and the pressure relief going off.

The pressure relief going off on the retract makes no sense to me either but I have very limited experience with hydraulics. I think on the retract the loader valve should be dumping directly back to the sump with no restrictions. The pump should have it easy just letting the boom down instead of lifting it on the way up.

Thanks for your insight. I'll keep trying to troubleshoot. Jim

 

[J_J]

Is there perhaps a mechanical binding on the bucket hinges.

You might remove the cyl ends to the bucket and see if you can push and pull the bucket by hand.

To make the relief go off in curl, there has to be some kind of resistance/load on the cyl .

 

[jsdepottey]

I got a chance to go out and work on the tractor tonight and found a major issue. I disconnected the "out" from my loader valve to confirm there wasn't any restrictions in the hose back to the sump. I was able to see the hydraulic fluid flow out from the valve using the bucket curl but nothing from the boom unless I pushed into float position. I'm starting to figure out why I got such a good deal on the valve. Not sure why the valve would be configured this way. It's a Husco valve, I'm not sure if I can have the spool piece changed or if I have to get another valve. Hopefully tomorrow I can get out there and swap the curl and boom hoses and see if that improves the speed of the boom.