Case DH4B Trencher/Backhoe Won't Spin Trenching Chain

   / Case DH4B Trencher/Backhoe Won't Spin Trenching Chain #1  

r8f1k

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Tractor
Farmall 100, Allis Chalmers D14, International Super MTA, IH 560, Mahindra 4510, Gehl 4500, Clark CY45, JD 800, JD 60
I just acquired an older DH4B, Mitsubishi diesel, runs fantastic, backhoe works, but the trenching chain does not. If I pull the lever to move the chain forward or backwards, it will move JUST SLIGHTLY. Maybe one tooth, then stop. You can hear the hydraulic pump working, but nothing is happening. The linkage on the pump is free and you can see it move no problem. On top and on bottom of the pump looks to be two compression style clamps that turn a rod that passes all the way through the pump. They look like they can be adjusted, but I am afraid there is something more going on here. I have plenty of hydraulic fluid and the engine revs up just fine when more RPMs are needed. I should also note that the push blade in the front does not move at all. It is almost like there is no hydraulic pressure going to the valve body. I am wondering if I am missing a hydraulic line altogether. Any ideas would be great.

*Update, I disconnected the hydraulic pressure line to the trencher hydraulic drive motor, when I did that I can turn the digging chain around a whole lot more. When I pulled the hose, water came out of the hydraulic motor, it is January up here in the north and I was wondering if the motor was full of ice. Gonna let it thaw out in the shop.
The thing that I am wondering, is that I am seeing on the parts diagrams a 'selector valve' for the hydraulics. With the trencher not working AND the back fill blade not working, could there be a selector valve that I am missing? Is the hydraulic system split 50/50?*
 
   / Case DH4B Trencher/Backhoe Won't Spin Trenching Chain
  • Thread Starter
#2  
Checking the internet, I found my model and I see in this photo another hydraulic lever that I don't have. Is that the SELECTOR? My machine has been painted a second time and all the labels are gone.
 

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   / Case DH4B Trencher/Backhoe Won't Spin Trenching Chain #3  
Can you follow the hoses from to the pump to see what they connect to? This should provide a starting point on what valve or valves are in that circuit. From your initial description of the pump control I am wondering if that is a hydrostatic drive with no directional valves in the trencher circuit.
 
   / Case DH4B Trencher/Backhoe Won't Spin Trenching Chain
  • Thread Starter
#4  
I can try, it is a NEST of hoses. There are two pumps on the back of the engine, I can hear the one on the right start to click when I engage the lever. I hope it isn't bad.......The machine is a hydrostatic drive for propulsion, not sure if it is for the trencher.
 
   / Case DH4B Trencher/Backhoe Won't Spin Trenching Chain #5  
Can you tell What the lever that operates the trencher connects to? A directional valve or pump control linkage?
 
   / Case DH4B Trencher/Backhoe Won't Spin Trenching Chain
  • Thread Starter
#6  
The trencher control is a cable driven lever, forward, neutral and reverse. The cable pulls on a shaft that runs up and down in the center of the right side hydraulic pump behind the engine. I assume it is simply changing the direction of flow to the hydraulic motor under the seat. I wonder if I disconnect or make the fitting loose at the motor and see if I have pressure, that will determine if the problem is the motor or the pump?
 
   / Case DH4B Trencher/Backhoe Won't Spin Trenching Chain #7  
If directly controlling pump sounds like hydrostatic drive. This requires a closed loop to prevent damage to the pump. Disconnecting one hose to the motor will allow to escape this loop and if enough oil escapes will damage the pump. The fact that engine grunts and chain moves a little points towards pump trying to work.

Do you have the capability of installing pressure gauge in the lines at the motor? This will tell you if you getting pressure to the motor.
 
   / Case DH4B Trencher/Backhoe Won't Spin Trenching Chain
  • Thread Starter
#8  
I can buy a gauge and work from there.
 
   / Case DH4B Trencher/Backhoe Won't Spin Trenching Chain
  • Thread Starter
#10  
Fluid level is just above the FULL line. I drained all the old fluid out before trying to start the unit up, I wanted to make sure any trash, water or sludge that was in the system was removed prior to circulating it through the system. Took about 13 gallons to fill it up, not including what was still in the hoses.
 
 
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