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Stuck spool valve on I-600 backhoe mounted on HD4

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Daelric View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Daelric Quote  Post ReplyReply Direct Link To This Post Topic: Stuck spool valve on I-600 backhoe mounted on HD4
    Posted: 06 Oct 2021 at 7:25pm
Hi all,

So after doing a bunch of maintenance on my recently acquired machine (doing a bunch of fluid and filter changes) I went to use it today and ran into a big problem.

Note: prior to doing all the fluid/filter changes I did play around with the machine a bit and did a good 2-3 hours worth of work with the backhoe digging up stumps, so this problem wasn't something I just hadn't discovered yet... this happened just now and it was functioning properly for me beforehand.

Also note that although I tried to do a full fluid/filter change where I could, there's no known filter to change out for the hydraulic system yet (as per Orangeman's list of filters for the HD4) so I didn't do anything to the hydraulic system other than top it up to the mark with 3 liters of 10W30 oil.

I went to do some more stump work today and I wasn't even 5 minutes into it when the dipper arm kept coming in even though I let go of the control rod. It came in all the way and you could hear that the system was still pulling on it even though it was fully brought in. A quick look around revealed that the control rod, although I let go of it, didn't go back to the 'neutral' position, and I can't force it back that way either. It would appear that the dipper spool valve is stuck in the 'pull in' position.

Now, I consulted the service manual and it sounds like I need to pull out the spool valve to free up whatever is blocking it. My question is, how in the world do I accomplish this! There doesn't seem like there's enough room, and despite having the service manual, the instructions for pulling a spool valve sound pretty complicated.

I'm wondering if there's an easy way to accomplish what I need to do, and any advice will be much appreciated.


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DiyDave View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DiyDave Quote  Post ReplyReply Direct Link To This Post Posted: 06 Oct 2021 at 8:53pm
loosen up the hoses, on the valve in question, to relieve pressure.  Then I'd try tapping it out with a hammer and punch. Just don't go ape with the hammer licks.  If that don't do the trick, I'd look for a relief valve that's stuck shut.  Be careful with hydraulic fluid that's under pressure!  I'd jack or block up the affected cylinder(s) to keep them from dropping, too.  Remember gravity still works as it always does...Wink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Daelric Quote  Post ReplyReply Direct Link To This Post Posted: 06 Oct 2021 at 9:29pm
I should have mentioned in my original post, is there a good way to access this control valve block that I'm not aware of? Because right now this thing seems next to impossible to get to without taking the hoe right off the HD4, which isn't really an option for me.... This photo was taken on my back looking up at the control valves from underneath. There doesn't appear to be any panels or anything I can remove to gain access as the rear of the backhoe frame is all one big welded-together piece.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Daelric Quote  Post ReplyReply Direct Link To This Post Posted: 08 Oct 2021 at 10:51am
Forgive my ignorance, but this one is driving me a bit batty. Trying to Google this isn't proving helpful. Can anyone help me out by informing me how to go about removing this style of linkage? I can't figure it out, partly because it's pretty hard to get at and get a good look at. These are where the control levers for the backhoe attach to the spool valve. I'm trying to remove the control levers to give myself more space to work and to facilitate removing the spool.


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Daelric View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Daelric Quote  Post ReplyReply Direct Link To This Post Posted: 08 Oct 2021 at 10:53am
The smallest piece of metal appears to be a retaining clip of some sort... I imagine with that removed I can just pull the pins out and remove. But it there a certain/special way this retaining ring/clip should be removed, or should I just haul on it until it comes off?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ray54 Quote  Post ReplyReply Direct Link To This Post Posted: 08 Oct 2021 at 1:49pm
Looks like a master link from a roller chain. Which I have seen on many control valves.


One end is slit using a small pick lift and pull it out over the end of the pin. It is spring steel so will bend. Then push the other side off the pin. Now slide it to the other end. The grove in keeper gets bigger and will come over the pin.


Would not surprise me that you will need to put new o ring on all the places that have them. Not rocket science but needs to be done with care. 


Try search terms such as "resealing a hydraulic control valve" or replacing o ring in valve.  Also see if you can find anything about master links in roller chain.  As I don't claim to be a descriptive writer and give good directions.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DiyDave Quote  Post ReplyReply Direct Link To This Post Posted: 08 Oct 2021 at 5:30pm
X2 on the roller chain master link.  I use a flat bladed screwdriver with the blade just a little wider than the  gap between the legs of the clip, just twist and pull on the screwdriver, and one of the legs will hop out of the slot in rides in.  In some instances, you have to bend the shaft of the screwdriver, to get it in where you want it.  Thank God for that drawer fulla cheap screwdrivers...Wink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Daelric Quote  Post ReplyReply Direct Link To This Post Posted: 09 Oct 2021 at 7:21am
Thanks to the tips here I managed to disconnect all that linkage finally! It was a bear to get the rod out holding the control levers as well, but it came eventually.

I'm at a point now where I'm feeling quite discouraged, as access is a real problem. I now need to get the bullet-shaped cap off, but it's super awkward to get to with the hoe attached to the crawler.

I'm thinking more and more that I need to stop messing about and take the backhoe off the crawler for this job. With the right wrenches I could probably reach up from underneath enough to get the cap and pressure relief valve out, but the chance of dropping something or otherwise not taking adequate care are very high due to the position I'm in underneath trying to reach up to this stuff. With the hoe off, I'd at least have all the room required to manoeuvre.

I just don't know what's involved with taking the thing off and, more importantly, how in the world I would get it back on again afterwards.





Edited by Daelric - 09 Oct 2021 at 7:24am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KRAKMT Quote  Post ReplyReply Direct Link To This Post Posted: 09 Oct 2021 at 7:59am
I pulled my valve body on my 715 backhoe and had it rebuilt last year. Was a couple hundred dollars well spent and gave me some peace of mind.

Mine had three bolts, took 5 hands and was heavier than heck but it works.

Working in that tight space would cause me to lose wrenches and my temper.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Daelric Quote  Post ReplyReply Direct Link To This Post Posted: 09 Oct 2021 at 8:31am
Originally posted by KRAKMT KRAKMT wrote:

I pulled my valve body on my 715 backhoe


Were you able to get it out without taking the backhoe off the machine?

I'll have to check clearances but I'm not even sure if I could do that with all the hoses detached and out of the way. It's really tight in there.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KRAKMT Quote  Post ReplyReply Direct Link To This Post Posted: 09 Oct 2021 at 4:59pm
it wasn’t bad on the 715b.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jim.ME Quote  Post ReplyReply Direct Link To This Post Posted: 09 Oct 2021 at 5:15pm
The cap at the bottom of the housing directly under that stuck spool is not a relief valve cap.  The cap on the bottom should be covering a centering spring arrangement for the spool.  If that spring broke or the screw (or what ever holds it) came loose it could be jammed up in the cap preventing the spool from moving back down.  


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Post Options Post Options   Thanks (0) Thanks(0)   Quote DiyDave Quote  Post ReplyReply Direct Link To This Post Posted: 09 Oct 2021 at 8:27pm
Cap is usually fine thread, too, IIRR. get it loose, then carefully remove by hand.  I've seen people burn, bend up or drill a hole in sheet metal that's in the way, to pull just one spool.  Don't be one of those people...Wink

Edited by DiyDave - 09 Oct 2021 at 8:29pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Daelric Quote  Post ReplyReply Direct Link To This Post Posted: 10 Oct 2021 at 11:22am
So, with everyone's advice on this forum and a couple different ones, I managed to get the spool out.

The first major breakthrough was figuring out that I can remove the seat, and then the bracket that the seat is attached to, which removes the back wall that was obstructing clear access to the valve block!


With that out of the way I could relatively easy get in and see what I'm doing.

I took the cap off the dipper spool and found what looks to be a pretty grungy screw.


I had to hook the linkage back up to the control level in order to be able to get the screw off without spinning the valve, but when I did get it off it was a spring assembly that was extremely dirty. And the spool itself still in the valve block wouldn't budge.

At this point I decided to take apart the spool next to it (bucket spool) to see if there was any difference between a 'working' spool and the faulty dipper spool. Sure enough, it was much cleaner looking (although still a bit grungy) and to my surprise, I was able to pull the entire thing out without taking the spring/screw off.

I reattached the screw to the dipper spool and tried pulling it, but no go at all. I ended up having to tap it out with a hammer and punch, which eventually worked, but holy was it ever stuck. At this point my guess, based on how the parts looked, is that water got int he system and was left too long, causing internal parts to rust and corrode to the point that the pitting and bubbling made it difficult for the thing to freely move back and forth. Even though it was working fine before, it was only a matter of time.

I ended up taking out every spool.


And then I decided to take off the entire valve block after pulling all the spools and disconnecting all the hoses.


At this point I'm going to take the whole thing apart and give it a good cleaning scrubbing.

What would be the best cleaner/solvent to use for this job?

Also, I'm left wondering what to do with the whole system at large. I'd hate to clean this thing up and then just throw it back on without doing anything with the rest of the system in case there's junk elsewhere that could get caught up. I need to take the pump apart probably and clean it too, as well as the diverter valve etc.

What would be the best way to flush everything out of the system after doing all that? I might as well do an FULL SERVICE on the hydraulic system after going this far!

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