Linkbelt/Case/JCB/Sumi I need hydrualic help!

[sawdustmaker]

I have a hydraulic gnome eating my lunch!
Let me start by saying I have 4500 psi from both pumps, and black smoke when it stalls the engine. The machine is a '96 3400Q link-belt with some particular hydraulic issues that i cannot find to save my life.
I have been focusing on the bucket issue since its the biggest nuisance, but ill mention all the issues since they might be related.

Bucket In/Out bogs engine excessively.
Boom up is not receiving dual pump flow.
Right track is much faster than left track with no load. (I have not checked with the pumps switched)
Neither track is very powerful even though together they easily bog down the motor up even a slight incline.

I have switched pump 1 and pump 2 outputs(and neg flow controls) with no effect.
Bucket in/out functions normally if "boom up" or "arm in" are called in conjunction.
I have switched the bucket 2/arm 2 pilot lines and the problem moves to "arm in" and "boom up" (the functions that pressurize the opposite side of the bucket 2 spool)
The pump control solenoid is working. (not sure if it reacts to load, but it does change pressures with modes)

Thanks in advance for any input.

 

[sawdustmaker]

I found some pilot line switched at the shuttle block causing the Boom 2 spool to not get any pilot pressure. This was also the reason that "boom up" and "arm in" were sharing the pilot line that was suppose to be "arm in/out". Based on the Paint on the pilot lines it appeared they had been switched since before the machine was painted in 2001.

The right track is still faster even after switching the pumps.

 

[funwithfuel]

Is your machine set up for hammer and shear ?

 

[John C.]

Travel problem is likely a swivel seal. When the travel motors go bad on those machine they get stuck in high range all the time.

 

[sawdustmaker]

It is not plumbed for any aux hydraulics.

I check pressures at the drive motors and see what I find.

 

[sawdustmaker]

That was supposed to say “I will check the pressures”

Im assuming that is how you would diagnose a leaking swivel. Correct me if I’m wrong.

If these drive motors stick in high gear when they fail, should I go ahead and pull this one before it gets worse?

 

[John C.]

I would suggest finishing your troubleshooting before removing large expensive components that may or may not have anything wrong with them. Is the weak motor the same in both directions?

 

[sawdustmaker]

They are both weak in both directions. The right one seems to be stuck in high range. When I did a pressure check I only got around 2500 psi at the pumps with the tracks stalled.

I have new issue now that “stick out” is getting two pump flow. Calling “stick out” from full in to full out will almost stall the motor. I do not know if the motor is perhaps a little starved for fuel, (I can’t find any screens in the banjo bolts) or if the computer is supposed to cut the pump back a little. It sounds the same as when tracking up an incline and it wants to stall.
It is a little funny about when it will track hard and bog the motor and when it will just load the motor and have not response from the tracks.

 

[jcb jeff]

I would do the basics of checking fuel system is all ok and engine is healthy as well.
Do a neg control pressure check this will tell you if any spools are stuck partial open or messing about i would put 2 gauges on so as you can record each service on both pumps as some combine flow.
Also check the wiring to proportional valve in milli amps as this is what changes your modes via the solenoid on the hyd pump.
Not 100 % familiar with the link belt but i guess you have the 8 bank solenoid same as case and jcb you can have a q max/ max cut should deswash the pumps to 60 %t which controls pump flow also the 2 speed travel solenoid is there as well which controls swash angle at the travel motors via a pilot line.
If your machine has got a few hours under the belt the swash plate can get worn in the normal operating area so can stick or break up.
The regulators on the pumps could also be a problem as these are not uncommon to fail.
Other things to consider are do you have check valves on the rams restricting flow .
I have had on the JCB stuff where the aux spool for the breaker although the machine never had a kit on the spool is still in the valve block and was drifting back and forth causing the pumps to drag the engine down but neg control test should show this up.
Other thing to consider the machine has not been set up in menu for kerosene engine or some one played about turning scarp mag or breaker on in the dash menu work a look as it dont cost.

 

[John C.]

The pressures for any function on that machine should be around 4,000 PSI. It sounds to me like you have big pump problems. Time to remove and check hydraulic filters for metal. Pull the suction strainer out of the tank and make sure it is clean. Is the pump making a lot of noise when you do something. Another thought concern an implement drifting down when you have it in the air. Damaged cylinders will put trash into the system cause the kind of problems you are describing.

 

[sawdustmaker]

I believe i may have found the cause of the tracking issue. Diagnostic credit goes to John C. Many thanks.

Edit: when i took the picture i had already pulled the top O-ring but the rest is untouched.

 

[sawdustmaker]

Here is a Video of how it was acting before i repacked the swivel, which was not difficult or expensive. Cost about $80 for the O-rings, packing, and shipping.

 

[sawdustmaker]

Unfortunately i have not found the issue with the bucket stalling the engine. I have plugged off the pilot line going to the bucket 2 spool for now so i can use the machine.
Also, even after putting the pilot lines back correctly, i still only have one pump flow to boom up.
Id really appreciate any help point me in the right direction getting the issues resolved.

Thanks again to John C for pointing me to the swivel as well as the plugged screen in the bottom of the lift pump.

 

[John C.]

As I recall the bucket function on those machines was supposed to be one pump while the boom function was two pump. When we installed dangle head log processor on them we switch the arm function that was two pump flow down to the bucket function and ran the process with it. You didn't need the stick to be real fast anymore so the change was quick, cheap and easy to do. It might be that some one has used the boom function for that instead. Check the routing from the main valve on down the hoses to the functions.

 

[sawdustmaker]

According to the service manual the bucket is suppose to have flow from both pumps when not under load. When loaded it shuts off the flow from the 5 spool side. There has never been any auxiliary on this machine as far as i can tell and i have checked all the lines over and over and everything is in the right place. The thing that still confuses me the most me is why it seems to deadhead the pump when the bucket 2 spool is stroked to the rear. Ill see if i can post a video of it in a little while.

 

[sawdustmaker]

Here is a video of my bucket issue with all the pilot lines hooked up right.

 

[davisgravel]

I know this is an old post but i have that same bucket issue, just curious if you ever figured out the problem?

 

[sawdustmaker]

No. Still running with a pilot line blocked off so it doesn’t stall. If anyone knows what causes this I’m still stumped.

 

[davisgravel]

Thanks for that reply, i just periodically check back here, if you do ever figure it out, please post solution here, and i will do the same. Thanks