Case DH4B Trencher/Backhoe Won't Spin Trenching Chain

[r8f1k]

Not sure. I have not pulled the spool apart. All the levers move, but I have not pulled the valve cap. Is it possible that the same thing is wrong with the trencher? Could that spool have a stuck valve? Or is that a different style valve?

 

[laurencen]

I have seen where the spool floats in the valve, the spool can stick in which case it does not move with the levers or not full stroke

 

[MTGreen]

Did you check to see if the relief valve is stuck open

 

[r8f1k]

Here are the photos of the spool in question. Here is a list of the problems I have found.
1) When used, NOTHING happens. Another user indicated that the spool might be plugged up or stuck. I began pulling the unit out and I saw something odd. All of the OLD fluid in the machine was RED. All of the NEW fluid is CLEAR. When I disconnected the lines that went to the cylinders, only RED fluid came out. When I pulled 'IN' hose, clear came out. That narrows it down to it having a blockage of some kind.

2) Pulled the spool out, tried to cycle through all three functions with air, not much happens. If I put air into the 'IN', and I cycle the spool closest to the 'BYD' port, SOMETIMES air will come out of the top port. I'm not sure what to do to clean it out. Any help on that would be great. Given that some of the fittings are RUSTY, how do you get them out?

3) One strange thing that I have a feeling about is the 'BYD' port. I can't get fluid or air to come out of the 'OUT'. There is only flow through the 'BYD' or 'IN' ports. If that is the case, the 'OUT' port has a hose going right to the trencher MOTOR. If this spool is blocked, could that mean that the motor will not work without a proper path of fluid? Is this the hang up with the whole trencher?!!!

 

[oldnslo]

There should not be any directional valves in the trencher motor circuit if it is being driven by the Sunstrand hydrostatic pump we have discussed in previous posts.



Depending on trencher motor style they might have run some tank line flow through the trencher motor case for cooling and flushing. Not common practice but possible.

 

[r8f1k]

Did you check to see if the relief valve is stuck open

Which relief valve, I do not know how to identify a/the relief valve

 

[r8f1k]

Does anyone have a recommendation for cleaning or clearing out a spool like this? Replacement is going to be difficult given that it sits down inside of the side of the excavator. Most newer spools have levers mounted much closer to the body itself. This unit has levers that sit 'higher' up. I'm not opposed to rebuilding the unit, I just don't know where to start......I don't really want to heat the unit up to get out the large flathead screws on top, but I guess if I have to, someone will chime in.

 

[oldnslo]

R8
Do all the spools move when you move the levers? If yes then the only repair would be seals on the ends under the covers and clean the centering spring mechanism.

On the rusted screw plugs. Remove one of the hose fittings and look down inside the port. I suspect those just may be plugs in auxiliary ports.

 

[r8f1k]

I don't think they always move. I have them soaking right now in my solvent tank. I will test again today with air and report.

 

[laurencen]

would those large screws above spool be pressure relief or restrictors to slow movement? I would take lots of pictures and take it all apart, soak in Diesel for a couple days, brass brush to remove gunk, use a brass bore brush in the valve body, thinking its totally gummed up inside