Case DH4B Trencher/Backhoe Won't Spin Trenching Chain

[oldnslo]

I can buy a gauge and work from there.

R8
If you install a gauge and this is a hydrostatic drive you should see charge pressure anytime the engine is running. Charge pressure typically is between 150 & 350 PSI. When you try to operate the trencher pressure should rise to relief setting if the trencher motor is not turning. Reverse the direction and gauge should drop to original charge pressure.

 

[r8f1k]

One thing that I have done as of today, is I changed all the filters on the machine, topped off the fluids and checked to see if there is any change. So far, none. However, I cracked the hydraulic line that runs to the hydraulic drive motor and turned on the trenching chain. NO REAL PRESSURE change at the motor. Is it possible that the pump is no good OR is it in RELIEF? I can hear it sort of 'engage' and chatter a little. There are a couple relief valves on the side of the pump, could they be loaded with trash? If not that, is it smart to pull the pump, take it apart, clean it and try again? How hard are piston hydraulic pumps to rebuild?

 

[oldnslo]

R8
Silly question but with fitting loose at the motor did you try operating in both directions?

Is the chatter you hear coming from the pump area? Can you feel the pump case to see if it gets warm or hot quickly when trying to operate? Does it chatter in both directions?

The relief valves are probably work port reliefs for forward or reverse so if chatters in both directions doubtful would be relief valves but anything is possible.


Dismantling and repairing piston pumps complexity varies with different manufacturers and control style. Main thing in cleanliness when reassembling.

 

[r8f1k]

I did try both directions, no change.

Chatter comes right from the pump. I don't run it too long, afraid to burn up what I already have. Chatters in both directions, not louder in one way or the other.

I'll pull the relief valves out and give them a wipe down.

Never pulled apart a hydraulic pump, not sure how to order new 'generic' parts which I assume is something you can do. I am a high school auto shop teacher and I have tore into lots of engines, transmissions, etc. and unusually you can buy generic bearings, seals, pistons, rings, valves, accumulators, etc. once you have measurements. Is there such a thing for hydraulic pumps? If so any good websites to order?

 

[oldnslo]

Seals and bearings should be standard sizes but the rotating group or pistons and cylinder barrel assembly are specific to a manufacturer. If you can find a make and model then parts should be easier to source. I will do some digging through my old stuff to see if I can find some service info for Eaton - Vickers products.

 

[r8f1k]

Thank you!!!!! I appreciate the help!!!!!

The pump I have has a tag on it:
18-2081R LH
87-11-80260

I think it is Case part number:
H672705

 

[oldnslo]

R8,
attached is parts break down on a Sauer Sunstrand (now Danfoss) series 40 pump. This will hopefully provide a visual aide in how these model pump is assembled. Other brands would probably be similar but none of the rotating group would interchange.

Hope this helps Vs hinders

 

[r8f1k]

I'm pretty sure that the pump that is in this machine is a gerotor type pump, anyone know where to get generic parts for a pump like that? I'm going to pull it out next week. I took the rear trencher boom off, trenching chain, etc. I need to rebuild the hydraulic cylinder that lifts the trencher, so I took all that off to make it easier.

 

[oldnslo]

R8
Are you talking about the hydraulic motor on the trencher or the pump being driven by the engine?

 

[r8f1k]

I'm talking about the hydraulic pump that is driven by the engine. I'm sure I can come up with generic o-rings, gaskets, but not the gerotor assembly.