All Hydraulics leak down

[regularjay]

I recently bought a Kubota B7200 2WD/gear trans with a 1630 loader. This thing has oodles of hours and certainly wasn't babied before I got it, but it does run and I'm sure I'll get it 100% eventually. For now I'm trying to figure out a hydraulic problem. This tractor came with a box blade that for now I'm just leaving on as it helps counterweight the loader. But, it won't stay up. It sinks to the ground in a minute or two and that just wont do. Im tired of continually having to raise it up every couple of minutes while I'm working. I would expect that perhaps o-ring for the 3-point lift cylinder might be worn but, the loader leaks down pretty fast too. I'm wondering if these two issues are related. I have no prior experience with Kubotas but I guess that the hydraulics are O.K. otherwise. Most hoses are recently replaced, nothing seems to leak and with a bit of finagling of load/dump the loader will raise the front of the tractor so I suppose the pump is properly strong I just have to get this leak down at both end issue addressed.

To be clear these are internal leaks nothing is on the ground (except my bucket & box blade LOL)

Also, I've got a hose running from a what looks like a fill port under the seat up to the loader valve, I'm guessing its the route fluid not used by the loader uses to get back to the resivoir it just seems kinda "cheesy" as the rest of the hydraulic stuff that doesn't need to flex is hard piped. Is this proper?

Thank you in advance for input or suggestions.

 

[b-rad-g]

If one or both of your cylinders are bleeding by internally it will cause your bucket to drift down. To test your cylinders on your machine you just retract the cylinders all the way, remove the hose or tube at the base of the cylinder, apply full pressure to the retract (rod) side of the cylinder. If oil pours out the open port you have a bad piston seal. This test can also be done on the rod side in the same way.

If all of your functions are drifting you could have some debris in your main relief valve. If this was your problem all functions would be slow and you would have a loss of power in all of your functions.

My guess is you have a couple of bad cylinders.

Good Luck!

 

[J_J]

Can you tell if any of your relief valves are working, you should have two. . A hyd gage will help you trouble shoot the hydraulic system.

 

[JoelD]

If one or both of your cylinders are bleeding by internally it will cause your bucket to drift down. To test your cylinders on your machine you just retract the cylinders all the way, remove the hose or tube at the base of the cylinder, apply full pressure to the retract (rod) side of the cylinder. If oil pours out the open port you have a bad piston seal. This test can also be done on the rod side in the same way.

If all of your functions are drifting you could have some debris in your main relief valve. If this was your problem all functions would be slow and you would have a loss of power in all of your functions.

My guess is you have a couple of bad cylinders.

Good Luck!

This is simple and great advice.

Thanks,
Joel

 

[regularjay]

This issue affects all functions of the bucket as well as the 3 point. The 3 point seems to be signifigantly worse than the bucket but the bucket will sink down and uncurl within only a few minutes.

Bucket lift cylinders were supposedly rebuilt by P.O. This unit seems to have decent strength (I have nothing to compare it to) and speed it just leaks down way too fast.

How would I know if my relief valves are working?

Thanks all,

Jay

 

[J_J]

This issue affects all functions of the bucket as well as the 3 point. The 3 point seems to be signifigantly worse than the bucket but the bucket will sink down and uncurl within only a few minutes.

Bucket lift cylinders were supposedly rebuilt by P.O. This unit seems to have decent strength (I have nothing to compare it to) and speed it just leaks down way too fast.

How would I know if my relief valves are working?

Thanks all,

Jay

Take out both relief valves and clean them. You will need a gage to reset them, and you need to know the operating pressure of the pump. If you are not sure how to do this, let someone who knows, do it for you.

When you extend the cylinder out to the limits, the relief valve should activate. and relieve. Same with the 3 pt. All the operation of hydraulics is dependent on how the system is plumbed. One area might affect another area, etc.

A relief valve is usually a spring loaded ball or plunger holding back the pressure until the spring force is overcome by the pressure of the hyd fluid, and releases some fluid to maintain a certain pressure in order to provide the operating force to the working parts of the hyd system, such as cylinders, hyd motors, etc.

 

[J_J]

On a loader valve, when the levers are in neutral. the cylinders ports are blocked. It would be unusual for 4 hydraulic cylinders to leak down in a few minutes. It would also be unusual for all the cylinder spools in the valve to leak down. If the valve and the relief is good, and if the cylinders are leaking, they will just equalize, the weighted side pushing the fluid to the unweighted side, and if you took off the out hose to the reservoir, no fluid should come out. If fluid comes out, then the loader valve is leaking or relief is leaking. If just one of those cylinders is good, then it should hold the bucket up.
Each set of cylinders has their own spool.

It seems like that there is a problem with hydraulic schematics for tractors, and other hydraulic machinery. Maybe they think that we do not know how to read, etc.

I have a set of manuals for my Case skidsteer, that covers the machine from the front to the back and everything inbetween. Including all electrical and hydraulic schematics.

I have nothing for my Power-Trac.

 

[SPYDERLK]

Even with a leaky piston a double acting cyl that has both sides filled cannot leak down in the compression direction if the ports are truly blocked. Compressing the cyl decreases its volume and the oil has to go somewhere. If it cant the pressure rises to the point that P X rod area will support the load ... or something blows first! Pressure can be very high in such case because of the small area and the relief valve is not in the circuit with the loader valve centered........ So if the arms drop w/o external oil in evidence the lift spool of the valve is definitely leaking.

To check the bucket articulation circuit in the same manner you must observe the cyls while applying compressive load. You can do this by 1st elevating the loader and setting the bucket level. Then place a stand under its lip and float the arms. If the bucket curls under this load the bucket spool is definitely leaking. In neither case have we proved that the respective cyl isnt leaking, but we know whether the valve needs fixing. After proving or getting it to work right the integrity of the pistion seal can be checked using loads that try to pull the rod.
larry

 

[J_J]

I deleted my other post because I was not thinking. Hydraulic lock is just that. If all the ports are secure/tight, nothing will move once set. That is not the end of the story, If the relief valve is in the work port circuit, then, if the load is greater than the cracking pressure, some fluid may leak out, and cylinders will drop a little. Certainly, if the spools are leaking, then the fluid from the cylinders have a place to go, and that is out the out port, and that is a good way to tell if the spools are leaking, is by take off the out hose from the valve, and observing any fluid flow.

 

[regularjay]

O.K. I was doing some work with this machine today and with an empty bucket about waist high I removed the cap from where the return lines goes into the tranny case. (Perhaps a Kubota specific thing, a hose runs from the loader valve to an aluminum fitting behind the gearshift. This fitting has what I assume is a fill cap on it and I'll further ssume that this fitting is screwed into what would be a regular fill port for hyd fluid if I didnt have a loader, seems to be the loader valve "return" path) Anyway with only the weight of the bucket I could see a very slight amount of flow through the hose. I mean very very slight. Could this be an indication of leaking valves in the loader control? Should the loader control seal 100%? I also noticed that the rate of leakdown does NOT seem to coorelate to the load in the bucket. Does that mean anything?

Thanks all!!

 

[J_J]

regularjay,

Just about all loader valves leak to some degree. The leakage is based on the specs that the valve is made. If the spools, and the valve body are made from different material, the expansion rate may be different. I don't think that anyone has done a consumers report on hydraulic valves, to give us an idea which valves are best, better, or just plain junk.

When the bucket leaked down with the hose disconnected, did the amount of fluid match what would have been in the cylinder? That would be a true test of a leaking valve. Do a 12 hr test with bucket up and tilted up.

If your loader valve is using the PB port, the leakage could be leaking out the PB port,or the valve out port. To check something like this, raise and tilt the bucket up, and shut off engine, then remove the hoses from the out port, and the PB port. As the lift arms. and bucket drop, you should see the results of a leaking valve. It would be hard to imagine two or 4 cylinders leaking, unless really worn out. The cylinders should leak down a little bit until the pressure equalizes, and if the valve spools are good, then they should hold in place.


A cylinder test can be performed by pressurized one side of the cylinder with fluid , and collecting the fluid from the other port to see if the fluid is bypassing the piston o-rings. Just about all hydraulic shops have the ability to test all your hydraulic items, cylinders, valves, relief valves, priority valves. etc.

Did you do your test while the fluid was cold, or hot. In theory, more load /pressure, should cause an increase in leakage, however, pressure/heat may cause a better seal.



Some valves are so bad, that one can watch the bucket drop. I have had my valves tested, and they tested good as for as the relief activated, and I don't know if they did a leakage test, as that would take some time for a non pressure test. My loader arms will drop from fully raised to full down in about 15 hours. As long as the machine will lift the rated load, I will have to accept that , as it would be difficult to be searching for that zero leak valve, but I could use a gate valve to shut off the cylinders, and keep the load up .

 

[regularjay]

I talked with my local Kubota dealer Friday and learned that a "seal kit" is available for this valve. The parts guy showed me the diagram of the valve with what looked to be just a bunch of O-rings for $65.00 He was unable or unwilling to speculate if replacing the o rings in my valve would improve my situation. I would really like to fix this for around sixty bucks instead of a couple hundred for a new valve. I have no external leaks at all so it would seem that fluid has to be "bypassing" inside the valve. Is it feasible to think new seals might cure this? I need this fixed but dont want to be further in the hole for a fix that isnt.

I did not disconnect a hose, the "out" port of the loader valve has a hose that goes into a "T" fitting on top of the tranny with a cap on one end of the "T". I removed the cap, and with the empty bucket elevated I could see a very small amount of fluid coming in through the "return" hose. The amount of fluid did not seem like near enough to account for the leakage but I don't know where else it could be going. The PB port I believe powers the 3-point which leaks down way faster than the bucket! I have ordered a replacement "O-ring" for the 3-pt cylinder and really hope that fixes that. A 12 hour test would waste 11:50 as my bucket even when empty leaks down in under 10 minutes.

 

[J_J]

Did you put the hose from the loader in a container, and collect the fluid for the time it took the loader to drop to the ground. If so, then you should have collected the amount of fluid in the cylinders. The only other place the fluid can go is from one side of the cylinder to the other side of the cylinder. You can rebuild the valve, but if the spools are worn, there is nothing that will fix that, even with new spools. The precision of these spools are not what you think. One vendor makes the valve body, and it might be made from one grade of steel, and the spool might be made from another grade of steel.and maybe another vendor makes the spools, and they only have to meet specs with a small variation. If a new valve leaks when tested, they remove the spools and reach in the bucket and install another one until it meets specs. So, even a new spool might not help, because the valve body of the spool might be worn. That is why some manufactures have posted that some leakage is acceptable, even to stating the amount of drops of fluid within a certain time frame. You can certainly rebuild the valve, and it just might fix the problem.

Just because the loader will leak down, does not necessarily mean the loader is not working right. In a static situation, like a loader fully raises, and engine off, there is a certain amount of force on some of the cylinders, caused by the down weight of the the loader. This pressure will vary based on the weight of an empty bucket and a full bucket, etc. Now, with the engine running and the pump building pressure, the pressure might help the seals do a better job at sealing by forcing the material to expand and do the job of sealing. However, if the seals or o-rings are weak ,torn, deformed, fluid will bypass and leak down, and you may not even see the leak on the outside.

I forgot to ask if you collected all fluid going back to tank. Normally fluid from the cylinders exit the valve via the out port, but when a PB setup is used, if the valve is leaking trough the PB port, that fluid is going back to the rear remotes and then to tank, therefour the question about did you collect all the fluid going back to reservoir?

 

[GE222]

JJ, Thanks for all the info. I have been reading all of the posts in detail for the original post. I have a Kubota B7200 that barely even lifts its 3-point. All I have done so far is to change the fluid, and clean the intake screen. My next step was to put a gauge in the system.

At engine idle, the 3-point won't lift, but at a higher RPM, it will go up but very very slowly. Once up it will hold pressure, and stay up. Unfortunately due to more pressing issues,I haven't had much of a chance to spend much time on this tractor, but lately, it is becoming more of a priority.

 

[relaqbr]

regularjay,

Just about all loader valves leak to some degree. The leakage is based on the specs that the valve is made. If the spools, and the valve body are made from different material, the expansion rate may be different. I don't think that anyone has done a consumers report on hydraulic valves, to give us an idea which valves are best, better, or just plain junk.<snip> My loader arms will drop from fully raised to full down in about 15 hours. As long as the machine will lift the rated load, I will have to accept that , as it would be difficult to be searching for that zero leak valve, but I could use a gate valve to shut off the cylinders, and keep the load up .

I am a newbie here and I have a question. I have a new scut which I am really happy owning but the fel drifts down just a little. So being a very **** person I want no down drift . However, I am realistic on occasion and so my question. How much is too much down drift. I appreciate JJ's comment on there being no consumers reports on hydraulics. And was wondering about anecdotal evidence from the group. I would also guess that the load and thus the diameter of the cylinders would come into play. So is 200lb in a fel with two 2inch cylinders that drifts down 5inchs in 24H too much? Great group!

 

[J_J]

That is probably less than most of us have . As long it will lift the advertised load, I would not worry about it.

 

[regularjay]

I appreciate all the interest/responses regarding my problem. I have purchased new "o" rings for my 3 point cylinder as well as the rebuild kit for my loader valve. Once I've installed everything I'll update this post with the results.

Jay

 

[soulasphil]

I used to have a 1960 Massey Ferguson 35 with a Massey loader (single action hydraulics) and it could be left with the loader up for several months, it would stay exactly as you left it. I now have a brand new John Deere 3520 and the picture is quite different. I use a hedge trimmer with 3 cylinders and a hydraulic motor which will drift down overnight ( have found it in awkward positions in the morning several times). The 60 D deck will come down in a matter of hours and the 300 CX loader will drift down to the ground in under a week. My dealer says it's quite normal, nothing to worry about. I much prefered the way the Massey behaved !

 

[J_J]

I appreciate all the interest/responses regarding my problem. I have purchased new "o" rings for my 3 point cylinder as well as the rebuild kit for my loader valve. Once I've installed everything I'll update this post with the results.

Jay

Everyone can appreciate your interest in a leak free valve, but you know the old saying, if it ain't broke, don't fix it. By tearing the valve down, you might make it worse. If you ordered the FEL o-ring kit, save it for when it really does leak, unless you really want the practice, taking something apart. Some valves do not even have o-rings, and rely on the manufactures tolerance for a good fit. If you ever get a valve that is leak free, then it probably has been tested over and over, in all temperatures, etc. Even the leak you think is in the 3pt cyl, might be in the 3pt valve. There are ways to test all hydraulics on the tractor, but is for the most part not practical.

I don't think they will ever get to the point of stating we have a maintenance free tractor.

Like some else said they could lift a bucket in the air, and it would stay there for months. Perhaps good valves, perhaps check valves.

Most people don't leave their buckets up anyway, primarily for safety reasons. Just let a kid jump up on your tractor and touch that lever, and his little brother is playing around the tractor, you will probably never leave the bucket up ever again.

 

[soulasphil]

The way you can store your tractor varies considerably. In my case, there's no way I can get it inside my 19th century granite shed unless the loader is up and the bucket down. Changing from the Massey to the leaking Deere means I now have to rest the loader on one of the cider barrels. Lowering the loader on the Massey implied first to change the position of two valves before the main control acted on lhe loader instead of the 3 pt hitch or trailer. Mice, bats or children have never managed to do that in the fourteen years I kept the Massey.