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Thank you in advance for any insight you may have and help…

Thank you in advance for...
Thank you in advance for any insight you may have and help you can provide. I have a 2006 287B xps high flow with a hydraulic issue when applying light pressure to the right hand joystick that controls the lift/tilt functions. When applying slight pressure to the joystick to perform a function slowly , the motor bogs tremendously! The issue is present when trying to lower the arms or curl the bucket in either direction, however it does NOT happen when lifting the arms. I have replaced the right side joystick assembly, pump control valve and the lift relief valves. At the pump compensator valve test port, I have nearly 0 psi with joystick nuetral which I've researched and concluded was good from a previous post. At the main inlet to the valvebody I have 375psi of standby pressure at idle which I've read should be around 350-420psi. When trying to perform the lower and tilt functions slowly, pressure builds to 3800psi as the pump strokes. During the lift function, I have under 2000psi and it functions smoothly. If you have any information that could help me I would appreciate it.
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Answered in 1 hour by:
3/9/2018
Mechanic: catmastertech, Technician replied 4 years ago
catmastertech
catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 4,041
Experience: Field service technician for CAT 19 years.
Verified

Hello,

I would check the leveling valve. It sounds like you have trash in the valve and it is restricting return flow from the cylinders.

This is normally located in the rear of the machine on the right side near were the cylinder lines come inside the frame.

The leveling valve is used to hold the load level while raising the arms. It sends some flow to the tilt cylinders during lift but, should not effect lowering.

However, when it is damaged or has debris in it, it can restrict flow both ways.

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Customer reply replied 4 years ago
I know exactly where it is located, I will go remove the diverter valve now and reply back to you with my findings shortly. Thank you.
Mechanic: catmastertech, Technician replied 4 years ago

Ok, thanks. If you need further help, please post the complete serial number with your reply.

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Customer reply replied 4 years ago
Catmastertech,
I removed the diverter valve and disassembled it. I found no contamination or stuck parts. I have reassembled it and put it back on the machine with no change in operation. Any more ideas? Serial is ZSA04142.
Mechanic: catmastertech, Technician replied 4 years ago

Have you checked the lift cylinders for damage?

Inspect the hole the cylinder is installed and look for any debris packed in the hole. If you find anything the cylinders could be bent.

Use a straight edge and check the rod and tube for bends.

catmastertech
catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 4,041
Experience: Field service technician for CAT 19 years.
Verified
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Customer reply replied 4 years ago
the lift cylinders appear to be in good condition. The machine has roughly 2700hrs on it. I have jumped the seat sensor so I can turn the key to run position and disable parking brake after running machine, under no engine power the arm comes down smoothly. Another symptom that might help you diagnose my problem is that when I lift the arms and return joystick to neutral the arms drift down. When I function the joystick to lower the arms, the pump strokes then I return the joystick to neutral and the arms drift up? I don't know if that will help you or not. This machine has really got me stumped so I appreciate any input you have.
Mechanic: catmastertech, Technician replied 4 years ago

It still sounds like a problem in the leveling valve. It contains some small orifices and they could be plugged.

If you did not remove the solenoid, remove it and check the stem inside it to see if it is stuck. This has been known to happen.

Does it change operation when you turn the leveling on and off?

I have been looking for some details on the valve but, the manual has no description beyond a simple schematic.

You might have enough room to bypass this valve by using a union fitting to connect the line from the valve and the one to the cylinder.

Then see if it is still present.

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Customer reply replied 4 years ago
I did remove the solenoid valve as well when I had the control block on the bench. From what I have found, the coil is energized when key is on and leveling valve switch is off inside cab. When the switch is turned on in the cab it de-energizes the coil.
I will note I took a plastic pen and pushed down the stem in the solenoid to make sure it wasn't stuck. While it was out of the control block assembly, I connected the coil to the wiring harness with key on and placed the solenoid valve inside the coil. The coil was magnetic so I know that's working, however the valve stem did not have much noticeable movement under magnetism. It was easier to push the valve stem in with the pen tip being under magnetism vs not, however it would not hold in the totally open position. I'm not really firmiliar with that type of a solenoids operation, does that sound normal or does it sound like a problem?Also turning on the leveling control vs off, it makes no difference in the operation. I tried that also.
Mechanic: catmastertech, Technician replied 4 years ago

I cannot say for certain how that particular solenoid operates but, I an use to the stem have a little slack when it is out and the oil is cleaned off.

Since it does not change the operation of the machine, I would try another solenoid.(###) ###-####CARTRIDGE AS-VALVE is the solenoid stem. Coil is separate.

I will post details on the leveling valve if you do not have a manual.

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Customer reply replied 4 years ago
I will see if my local cat dealer has one on hand tomorrow and report back to you with the result of a new solenoid. Any service information you can provide is greatly appreciated as I don't have the $800 service manual!
Mechanic: catmastertech, Technician replied 4 years ago

Yes, it is expensive but, you seem to be on top of the repairs already. A manual would keep you out of the shop for most repairs.

See the link below for the leveling valve details.

https://drive.google.com/open?id=1VysmYHhC9PfrVk4RQlN3UII4TxluZWlr

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Customer reply replied 4 years ago
Hello catmastertech,
I have replaced the cartridge valve on the work tool positioner block but it did not fix my problem. Another symptom I have noticed is when the lift cylinders are struggling to lower or retract, the tilt cylinders begin to extend. With the arms all the way down and bucket curled back(Tilt cylinders compressed), if I perform the lower function it transfers the fluid somewhere and extends the tilt cylinders. Do you have access to a hydraulic schematic that may be able to help me?
Mechanic: catmastertech, Technician replied 4 years ago

Do you have additional lock valves installed on this machine?

It is not common for them here but, they are an option in the EU.

You said earlier the lift cylinder lowers fine with the engine off.

Have you tried disconnecting the coil? any change?

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Customer reply replied 4 years ago
No I do not have additional lock valves that I know of. I was hoping to see where line C from the work tool positioner valve goes and how it transfers into the main valvebody. It appears a small piece of the c clip that's on the lower spool in the work tool positioner may have broke off and entered the valvebody from line C.
Mechanic: catmastertech, Technician replied 4 years ago

Have you tried capping of lines C and D?

They are just tee'd into the tilt lines. I don't know what will happen but, might show something different.

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Customer reply replied 4 years ago
I have not tried that yet, but it has came across my mind in order to rule out the work tool positioner. The hardest part for me in order to do that will be getting ahold of the proper plugs and caps! I'm going to review the snippets you have sent me and try to figure out the most probable spot that a piece of that clip could be lodged in the valvebody also.
Mechanic: catmastertech, Technician replied 4 years ago

You will need two -06 size ORFS caps and plugs for the tilt lines and two -10 ORFS caps and plugs for the lift lines if you want to remove it.

If you can fabricate a -10 ORFS male end hose, then you can remove the valve completely.

Here are the CAT part numbers for ORFS caps and plugs.

6v9831 -10 cap

6v9830 -08 cap

6v9829 -06 cap

6v9510 -10 plug

6v9509 -08 plug

6v9508 -06 plug

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Customer reply replied 4 years ago
Catmastertech,
I appreciate you finding out what fittings I needed to bypass the work tool positioner valve. I finally got two 6orfs plugs to plug the tilt lines and had a hose made to connect the lift line together today. I have totally removed the work tool positioner and have isolated the tilt and lift circuits at that point, yet the problem still persists. When I apply just enough pressure on the joystick to perform the lower function as if trying to lower the arms very slowly, the hydraulic pressure at the main inlet to the valvebody builds to ~3500psi as the pump strokes and engine bogs. Note, the arms are not moving down at this point, however the tilt cylinders begin to slowly extend. I'm thinking the problem is in the main valve or the shuttle valve at the bottom of the joystick. Any thoughts? Again, thank you for the support you have been able to provide.
Mechanic: catmastertech, Technician replied 4 years ago

WOW, this one is getting weird. I must do some extra deep research to find how this machine is made. I find three different schematics for this machine and don't see but a couple of changes.

One thing, no skid steer uses a variable flow pump. All are using a gear pump for implement and high flow pumps.

Only one version shows using a resolver on the implement joystick and it is to trigger high flow. This is connected to tilt rack back pilot line. However,

I am not clear on how that might load the pump so much.

Are you saying this only happens when feathering the hydraulic controls or does it even occur during full lever movement?

A different main control valve is also shown. Can you find a part number on your main control valve?

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Customer reply replied 4 years ago
This one has my brain scrambled! Correct, It only occurs when feathering the control, if you use full lever movement it seems to overcome the issue. I will go try to locate the control valve part number and get it to you.
Mechanic: catmastertech, Technician replied 4 years ago

I must correct myself. Some machines are using variable displacement pumps.

Do you see a part number on your pump?

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Mechanic: catmastertech, Technician replied 4 years ago

Have you tried adjusting the pump standby pressure and checking the margin pressure?

Is this machine marked "XPS"? If so, have you done the pressure testing for XPS?

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Customer reply replied 4 years ago
The machine is "XPS high flow" and I have not done any pressure testing with it. I have adjusted the standby pressure to ~375psi. It was up around 1100psi when I started my pressure testing, somewhere in my research I found it should be 350-420. I do not have the service manual with the proper testing and adjusting procedures.
Mechanic: catmastertech, Technician replied 4 years ago

I see this uses a special "load sensing" relief valve. It has some quirks with the setting and that could be your issue seeing the pressure jump when feathering.

I also found the pump compensator has know issues too but, they are described as "weak" operation.

I will attach the testing information for the margin pressure setting.

It will take me a few minutes to pull it together for you.

Here is the link to the testing guide.

https://drive.google.com/open?id=1eggew98PeSL9fHkNCVfwWMD3anBurDYB

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Mechanic: catmastertech, Technician replied 4 years ago

Those are the correct schematics of your xps valve and pilot

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Customer reply replied 4 years ago
Thank you for being so helpful. I will perform these test and hopefully report back with good news!
Mechanic: catmastertech, Technician replied 4 years ago

I hope this helps narrow down this problem. I am sorry I didn't catch that first.

Most of my work on these has been the smaller and older models. The newer machines are out in my area but, I am not called on them much anymore.

Just keep me posted and we will figure it out.

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