Stuck trying to fix hydraulic problem

[Chaslynch]

Hi, I have recently bought an old Kubota k008, the blue model made around 1999.
I did notice the blade was drifting down slightly in the couple weeks I have had it, but now it has completely failed and will not come back up.

As you operate the lever you can see the pipes move and it does try to move up at idle, as soon as you turn up the throttle it looses the little power it has and falls to the floor.

This model has expanding tracks which must be on the same circuit as the dozer blade, there is a switchover lever for them.
The expanding tracks seem to be fine, as does every other ram on the digger.

Initially I took apart the dozer ram and had it rebuilt with new seals, this did nothing to fix the problem.
Next I took apart the switchover lever block, but again this seems fine.
I'm concerned it will be a problem with the rotary joint , or the valve block.

But I don't want to mess with anything unnecessarily, and I'm already heading down that road.
I simply don't have the money to get a fitter out,

I would love some guidance on how to diagnose the faulty component,
If anybody could share some wisdom I would really appreciate it.

[Muz]

Welcome to the forum a simple hose joining would have proved the ram wasnt at fault, but hey .. you've passed that stage and at least eliminated that part of the problem so that leaves you with a damaged seal in the orbital valve, or a problem with the spool. However on this machine theres a third component, as youve seen, the changeover valve that puts the tracks out which is in the same circuit as the dozer ram, because the track extension is not loaded like the weight of a dozer blade to fall down, that part of the circuit would seem fine, so .. keeping things simple at first as always, you want to check the changeover valve , and make sure it is actually switching off completely and that the lever is allowed to travel all the way up or down without impingement , if it seems fine you may also need to block it off and take it out of the circuit to 'prove' that its not allowing oil to bypass.. you'll need to get some BSP caps to seal off the feed hoses to do that I'm afraid, but they are pennies, before you start digging deeper. I notice on some of mine that when the tracks reach the end of their extension, the dozer takes a wee dip, so pressure must be escaping somehow, though, in all the blue ones Ive owned, Ive never had to repair an orbital valve when I owned them .. but if you're sure the changeover valve is ok it would seem the orbital a likely candidate

[Chaslynch]

Hi muz, thanks for taking the time to reply. I have 4 questions , as you can probably tell, this is my first machine and it's a steep learning curve for me.

1 . How, for future reference would I tell the dozer ram was ok by joining the pipes, am I missing something simple here.
2. The changeover valve looks fine and all working, I was surprised how simple it was inside. But how would I take it out the circuit? Is it just by joining the feed pipe , to the other 2 pipes ,one after the other?do I join the pipes with a fitting.
3. Do you know off hand the size of the BSP caps (and straight connector?) I would need, ?
4 do you know of a way to prove if it is the lever control valve or the rotary joint,?
Thanks for the help it's a step in the right direction.

[Muz]

Hi muz, thanks for taking the time to reply. I have 4 questions , as you can probably tell, this is my first machine and it's a steep learning curve for me.

1 . How, for future reference would I tell the dozer ram was ok by joining the pipes, am I missing something simple here.
2. The changeover valve looks fine and all working, I was surprised how simple it was inside. But how would I take it out the circuit? Is it just by joining the feed pipe , to the other 2 pipes ,one after the other?do I join the pipes with a fitting.
3. Do you know off hand the size of the BSP caps (and straight connector?) I would need, ?
4 do you know of a way to prove if it is the lever control valve or the rotary joint,?
Thanks for the help it's a step in the right direction.

Its just basic plumbing .. you just have to block off feed pipes to work your way back to the problem ... the selector valve for tracks is the only unusual part in this equation ,, and a guage is helpful sometimes to observe pressure dropswhen plumbed in line

[2414.ginger]

Just a quick question from the idiots point of view (mine), if it's the orbital, wouldn't the escaping oil that doesn't get to the dozer, then power up something else, like a track or indeed the expanding tracks? or would it just return to tank?

[AndrewMawson]

When I had a K008 (now sold) the changeover valve handle was extremely vulnerable being just where left boots tend to go. When I got it the lever was actually broken with the result that when operated it didn't move full travel. Iirc it is only a little oval hole that locates it on the spool, and that was wallowed reducing movement even further. It got fettled 😀

[Chaslynch]

Ok guys , back again.
I did Various tests today , proving that the ram and changeover valve are working.
Next I have to look at the control vaves or orbital joint.
Not being able to narrow it down I tried the control valve very carefully took it apart after reading as much as possible to try not to cause any more problems.

Anyway I got the valve out, but I can't see what could be wrong with it. There are just 2 o rings, one at either end.
How do these fail? What should I be looking for?
Thanks

[Muz]

Anyway I got the valve out, but I can't see what could be wrong with it. There are just 2 o rings, one at either end.
How do these fail? What should I be looking for?
Thanks

All it takes is a small score on one . or the surface or shaft they mate on , or more commonly for them to go hard, and not seal effectively, they should be soft and pliable.

[Muz]

Just a quick question from the idiots point of view (mine), if it's the orbital, wouldn't the escaping oil that doesn't get to the dozer, then power up something else, like a track or indeed the expanding tracks? or would it just return to tank?

Yes you would think so, and indeed I said that earlier where you dead end the extension ram and it makes the dozer one move as you do so and also some of these valves have a drain line that allows oil to vent from the valve.

[Muz]

Ok guys , back again.
I did Various tests today , proving that the ram and changeover valve are working.
Next I have to look at the control vaves or orbital joint.
Not being able to narrow it down I tried the control valve very carefully took it apart after reading as much as possible to try not to cause any more problems.

Anyway I got the valve out, but I can't see what could be wrong with it. There are just 2 o rings, one at either end.
How do these fail? What should I be looking for?
Thanks

The next option here is to remove the dozer ram from the orbital valve flow and check it outside of the valve, all you would need to do is isolate the feeds going into the valve and connect them directly to the dozer ram , it would mean you need some extra hoses though to do this, but it would eliminate the orbital valve or prove it is the culprit, because its a fair job to do those seals

[Chaslynch]

Hi, right advice has been followed, thanks for the input.
It was showing the rotary joint as the problem, so I have been working on getting to it through the week.

Finally got it out and apart a few hours ago.
There are 7 o rings inside, I'm 99 Percent sure there should be 8, but I will find a diagram to check that.

2 of the o rings are chewed up badly, and they are all very brittle, there's little bits of them broken off inside.

Also, I found a large washer in the bottom of the digger which I think should be part of the joint which has been left out at some point, but again I will check that.

I have taken some pictures , is there a way to upload them
So all in I suppose that is a positive situation as that should be the fault
I have still got a lot of work to do putting it back together but I feel like I'm getting somewhere now.

[ianoz]

Mate , Once Muz reads your post , he will ok your photo posting rights .. new members can't post photos or links etc straight off . keeps the spammers at bay.

[Chaslynch]

Ok mate, that makes sense, thanks

[Muz]

Ok thats good you've isolated it .. you are a full member here so posting pics is all go

[v8druid]

Hi muz, thanks for taking the time to reply. I have 4 questions , as you can probably tell, this is my first machine and it's a steep learning curve for me.

1 . How, for future reference would I tell the dozer ram was ok by joining the pipes, am I missing something simple here.
2. The changeover valve looks fine and all working, I was surprised how simple it was inside. But how would I take it out the circuit? Is it just by joining the feed pipe , to the other 2 pipes ,one after the other?do I join the pipes with a fitting.
3. Do you know off hand the size of the BSP caps (and straight connector?) I would need, ?
4 do you know of a way to prove if it is the lever control valve or the rotary joint,?
Thanks for the help it's a step in the right direction.

Hi
you'll have two pipes going to the change over valve .... and 4 coming out ..... 2 go to the blade cylinder and the other 2 to the track extensions.

connect the two feeding the valve to the pipes connected to the ram and you will have taken the valve out of circuit.

as a matter of interest are the track extension/retraction functions working ok???