Case DH4B Trencher/Backhoe Won't Spin Trenching Chain

[r8f1k]

Large update. I installed the new hydraulic pump, I plumbed the motor spool to the hydraulic motor, filled the system back up and SHE WORKS!!!!! The chain spins, the hydraulics do what they are supposed to do. I don't have the digging chain back on, but the drive chain works perfect.

I only have one other issue and the the front backfill blade, still does not work. I dug into the unit pretty far and I found that the steering pump and the backfill pump are the same. Both features take pressure from the same pump, one works, one doesn't. So, I think the spool is no good. Not really interested in tearing into the spool again. I am thinking that if I get the system nice and hot, I wonder if the spool will loosen up enough to do something. If not, I think I will have to swap it out.

I also had a terrible thing happen upon the first start up after a couple weeks of sitting. I started it up, ran for about 10 seconds and I heard a loud ping come from the front of the engine and I saw the upper radiator support bolt fell out of it's hole and the fan hit the bolt, making a tiny hole in the radiator. Over 4 hours of sitting, it made a puddle the size of a silver dollar. I am thinking that I best off putting some stop leak in it, use it for now and look for a rad. There is a shop not too far from me, but I just got this thing together and I would like to run it for a while and then take the radiator out in the late fall once the machine is put away for the winter.

 

[Mike1955]

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?*

From your description it sounds like a shard is slipping inside a sprocket

 

[4570Man]

I haven’t read the whole thread but my Vermeer has a diverter valve to switch flow from the digging chain and the plow vibrator. Only one of the 2 can be used. If it was set to the plow vibratory the digging chain can’t move. It also has a diverter valve on the blade. It’s a 6way blade but only has dedicated 4 way function. The other 2 functions share a diverter with something else.

 

[Fixastuff]

I haven’t read the whole thread but my Vermeer has a diverter valve to switch flow from the digging chain and the plow vibrator. Only one of the 2 can be used. If it was set to the plow vibratory the digging chain can’t move. It also has a diverter valve on the blade. It’s a 6way blade but only has dedicated 4 way function. The other 2 functions share a diverter with something else.

What vermeer to you have? I have a rt650 plow/trencher.

 

[4570Man]

What vermeer to you have? I have a rt650 plow/trencher.

V4150.