Oil & Fuel LA680 Spool Valve LEAK (spewing oil) Problem

[npaden]

Well, I never figured out what was causing my problems with my L4200 last year, but it has been working well for the last several months so I'm hoping it was just some bad fuel or something.

The new problem is that this weekend doing some brush clearing hydraulic fluid started spewing out of the top of the control valve whenever I tried to curl the loader bucket. Nothing physically contacted the valve that I am aware of, but after cleaning it up you can see the O-ring poking up out of the control valve. I can lift the bucket up and down with no issue and curl the bucket down with no issue, but if I try to curl the bucket up oil SPEWS out the top of the control valve and the bucket doesn't curl up even with nothing in it.

Looking at the parts diagrams there are o-rings and wipers and a complete seal kit that I can order, but reading older posts, I'm worried that the o-ring really isn't holding back any pressure and there must be another issue inside the valve. Looking at the rod that moves up and down inside the cylinder I don't see any knicks or dents anywhere on it that is exposed.

I highlighted the area that is leaking in the diagram:

Is this something that I can order the kit and just change out the o-rings or is this something I will need to take to a hydraulic shop for a rebuild? If so, on a 13 year old machine that seems to have had a fairly hard life prior to me owning it is it a good idea to replace all the o-rings on the control valve or just the one that is currently leaking?

Thanks, Nathan

 

[npaden]

Well, I went ahead and picked up a seal kit, the local dealer actually had one in stock!

I'll attempt to replace the seals tonight and let everyone know how it turns out.

 

[npaden]

Good news, I replaced the seals and everything went fine.

Bad news the bucket still won't curl!

Turns out the valve cylinder that I replaced the seals on controls the boom. I just assumed that it controled the curl since when I tried to curl the bucket it spewed hydraulic oil out the top of that cylinder. There was no doubt that the wiper was toast in that cylinder though and I guess when it was trying to curl it found the path of least resistance and came out the top of that cylinder since they are connected.

When trying to curl the bucket, hydraulic oil weeps out the other valve cylinder but nothing excessive. The curl cylinders on the loader seem to be fine, I can't see anything visually wrong with them. It still curls down, just not back up, although it is up against the stop all the way down now and I can't get it to curl back up even a tiny bit now.

Any thoughts?

Thanks, Nathan

 

[npaden]

Well, I swapped the curl and the boom hoses and the bucket curled fine and dumped fine as well so the cylinders on the actual loader aren't an issue.

I lifted the boom up (it was now hooked to the suspect control valve) and it got about 1/2 way up (with nothing in the bucket) and BOOM, hydraulic oil spewed all over! After inspection it turned out to be a hose that feeds the control valves. It popped off at the quick connect and split the hose near the control valve for good measure.

Then I could lift the boom fine, (with some oil pouring out the massive rip in the hose) but it wouldn't go down at all. I disassembled the suspect control valve and as I was taking it apart I could move it slightly and get the boom to come down very slowly. I never could get it to go all the way to the ground so when I took it apart the last bit I got a nice puddle of hydraulic oil under the tractor.

The suspect control valve looked fine upon closer inspection. The o-rings were all in decent shape, but it seemed like there was nothing stopping the o-rings from traveling up and down the rod. Of course I might have just not noticed it until after I had the rod completely pulled out of the cylinder.

I'm debating putting a seal kit in just for grins and seeing what happens. I'll be very gentle and hopefully won't pop another hose.

Is it a lost cause and I just need to bite the bullet and buy a new valve cylinder? I looked it up and it is $440 at Coleman Equipment - http://www.colemanequip.com/Kubota_Parts.asp?page=&q=75540-61400

I've heard a few folks talk about having a hydraulic shop rebuild them. Is that a viable alternative?

Any suggestions?

Do I need to move all this to the hydraulic forum?

Thanks, Nathan

 

[KennyV]

Hello Nathan ...
Just came across your problem and can not look into it at this time, it will be Wed evening before I will be able to get back to this, hopefully someone will get back before then... KennyV

 

[npaden]

Well, after a big scare, I think everything is actually working and no leaks!

I changed the seals out in the other control valve cylinder, (pretty easy actually) and put the new hydraulic hose on and put everything back together today after work.

Started her up and the hydraulics were completely dead. The 3 point lift didn't work, and nothing on the loader worked. Pretty scary.

I did think of all the hydraulic oil on the floor, so I ran out and bought some more hytran fluid (I ended up buying a brand at Autozone that said it was equivalent to Kubota UDT, is it bad to mix hytran oil). I added about 2 gallons and didn't ever notice the sight glass move, but I thought surely I must have added enough and I started it up again and the hydraulics were still completely dead. I started to feel sick. I knew that it couldn't have leaked 2 gallons since it was working last night. I started adding some more and noticed the level start to register on the sight glass. At about 2.5 gallons I was almost to the middle of the sight glass and I started her back up. (At the time I bought it, I was thinking the 5 gallon pail was overkill but that's the only size they had it in).

After a second of nothing the 3 point lift sprang to life!! Then the loader started working, and it raised and lowered the boom, and curled and dumped the bucket!!!!!

I ran it through several cycles and everything seemed fine. I didn't take it out and actually try to dig or put any extra pressure on it, but I'm thinking there must have been something blocking or jamming that control valve cylinder. When I took it apart last night it seemed like there was an extra o-ring down on the rod where there shouldn't have been one, and maybe that was it.

So, a few extra hours of repair time, but the seal kits cost less than $50 and everything else including the 5 gallon pail of hytran was about another $50 so a pretty inexpensive repair in terms of $.

Hopefully when someone does a search they can see that this isn't a very difficult repair and it can solve what seemed to be a very big problem at the time.

Thats it from this end. Hopefully nothing else breaks anytime soon!!

 

[npaden]

Nothing too exciting, but I did take a few pictures of the repair.

Here is the control valve.

You might notice that on the cylinder closest to you in the picture that the bolts have regular flathead screwdriver heads. It seems like everytime I go to make a repair on this tractor, someone has been in there before and jimmy rigged it. Not only did they not use the allen head bolts that were there to start with, they didn't use kubota washers and wipers, but I think they doubled up on some thinner washers and used some flat wiper they happened to find that fit. I think that's what ended up happening is that one of the smaller o-rings must have slipped down inside the valve. Needless to say, the flathead bolts were a pain to remove and have now been replaced with allen heads.

One bit of input if someone tackles this and finds themselves with some ball bearings and a spring laying on the ground when they take the bottom of the control valve apart like I did.

The trick is vaseline! It is actually good on hydraulic systems and came recommended by a tractor mechanic I know as well as the Kubota dealer when I talked to them about the repair.

I just gooped some vaseline on the ball bearings and it held them in place while I slipped the rod back in the sleeve.

Nothing too exciting on the pictures, but it is back together and working!