Case DH4B Trencher/Backhoe Won't Spin Trenching Chain

[r8f1k]

No change. The gauge moves just above 100 and that's it

 

[Doaaj50]

In both directions?

 

[oldnslo]

R8
Can you physically see the control shaft on the pump? It should rotate approx 15 degrees either direction from center.

 

[r8f1k]

Yep, it moves. I can see the shaft moving. Both directions, no difference. It is low on fluid, so I am going to add more before I condemn it, but I have a feeling the issue persists. Is it possible that the lever isn't turning the shaft enough? Like it is staying in between neutral and forward/reverse. I am waiting on a new control cable, hydraulic fluid, a tire and one hydraulic fitting. Once I get all of my supplies, I will give it another go. Right now the machine is in my shop and I would prefer to test everything outside. I also pulled the thermostat out and it was pretty plugged up. I want to get the cooling system nice and clean as well since there is a HUGE oil cooler in front of the radiator and I'm sure that plays a role in keeping the fluid in good shape.

 

[Doaaj50]

So there is only 2 possible explanations to what you have happening.
1. The pins (12) that attach the shaft (6) to the swashplate (11) have either sheard off or fallen out. This would cause the swashplate to remain in a neutral position, even though you are rotating the shaft.

2. There is a tremendous leak somewhere else in the system.

Are the system hoses from the pump connected to the motor?

If they are, the next step I would do is cap them and try to stroke the pump. I would do this right at the pump so there are no other potential leak paths availble. This is a "dead head" condition so the oil will immediately go over the relief valves which are probably around 5500psi. You should immediately hear the pump whine and the engine should labor. Do not fully stroke the pump since those valves aren't going to be happy with full flow going across them. I would also make sure you take out the 600 psi gauge because in one direction it will be destroyed.

If it passes this test, then the issue points more towards the trencher motor, not the pump.

 

[oldnslo]

Doaaj50,
Since you sound far more familiar with this Sauer unit would both control shaft rotate if the pins was missing on the side being driven?

Does this model have work port relief valves? Just curious since I know some Eaton units had the reliefs in the motor.

If major leak would he see charge pressure or would it drop?

 

[r8f1k]

So there is only 2 possible explanations to what you have happening.
1. The pins (12) that attach the shaft (6) to the swashplate (11) have either sheard off or fallen out. This would cause the swashplate to remain in a neutral position, even though you are rotating the shaft.
View attachment 783288
2. There is a tremendous leak somewhere else in the system.

Are the system hoses from the pump connected to the motor?

If they are, the next step I would do is cap them and try to stroke the pump. I would do this right at the pump so there are no other potential leak paths availble. This is a "dead head" condition so the oil will immediately go over the relief valves which are probably around 5500psi. You should immediately hear the pump whine and the engine should labor. Do not fully stroke the pump since those valves aren't going to be happy with full flow going across them. I would also make sure you take out the 600 psi gauge because in one direction it will be destroyed.

If it passes this test, then the issue points more towards the trencher motor, not the pump.

I would say that there isn't a big leak in the system. The reason I say that is there are 3 pumps on the drive plate. The left hand pump runs the excavator and the boom lift of the trencher. The middle pump runs the drive wheel and steering. The RIGHT hand pump, our troubled one, runs the trencher motor and the backfill blade. The back fill blade does NOTHING. I would think if there was an issue with the trencher motor, the blade would still work and vice versa. My question is, should I wait to try the system again with all the oil, or should I go back and remove the oil that is currently in the system and pull the pump out to check for the pins? Are they roll pins? Do they commonly shear or fall out?

 

[oldnslo]

Is the backfill blade operated via a hydraulic cylinder? If yes I highly doubt it is driven by a hydrostatic pump. Hydrostats require a closed loop flow path where oil flows from the pump to the consumer typically a motor and from the motor back to the pump with equal flow rates. A single rod cylinder does not provide equal flow rates from rod end to cap while operating. You would also have to incorporate a diverter valve to operate either the trencher motor or backfill blade.

 

[r8f1k]

So, my assumption is that the pumps operate a number of things, but can't do it all at the same time. There is NO DIVERTER valve. Was it removed? I have no idea. Perhaps someone declared the trencher 'dead' and decided that it could just be used as an excavator and took hydraulics out? The backfill blade has a 3 spool control, none of the controls do anything, but the lift trencher lift cylinder does work and it is plumbed on that same side. If a diverter valve is missing, where would it pull hydraulic pressure from? The left hand side pump? If so, then I assume you are splitting from backfill to trencher lift cylinder. However, I still have the issue of the trencher motor/pump. Is there a way to test the motor in place?

 

[oldnslo]

Any idea on what style or brand of motor is on the trencher? Depending on style there may be tests that you can do.

I think you either need a hydraulic schematic or will have to start tracing hoses on the pump in question. At this time We are just guessing or speculating on how it is plumbed.