Used/rebuilt Kioti loader control valve options

[4lane]

I've been trying to diagnose my loader dropping on my Kioti CK30 (KL130 loader), and the consensus is that..

1. the dropping itself cannot be due to just the cylinders leaking themselves. The problem must be either the control valve and cylinders OR just the control valve. Either way, the control valve is leaking.

2. Because the tolerances in the control valve spools are so tight, it's not possible to replace just the spool valves

If the entire control valve needs to be replaced, is there any place I can source a used/rebuilt replacement instead of buying new? Any and all input/recommendations are helpful.

 

[K5lwq]

I don't know of a place to get used valves. However, I will say that all valves leak internally, to some degree. Some more than others.

Most valve manufactures will provide that information on their spec sheets. It is usually in CC/min. I just finished sourcing a new valve myself and I noticed some have as high as 15cc per minute. The one I purchased is rated at 2cc per minute at 1500 PSI.

If you have a cylinder bypassing then it can make a huge difference in how fast things leak down. I would start with testing the cylinders for bypass and go from there.

 

[oldnslo]

Like K5lwq states check the cylinders first. Unless some big piece of debris got caught in the valve and scored the bore or spool the valve leakage will not increase dramatically in a short period of time.

Frequently fixing the cylinders will get the drift rate back to an acceptable level.

 

[4lane]

Like K5lwq states check the cylinders first. Unless some big piece of debris got caught in the valve and scored the bore or spool the valve leakage will not increase dramatically in a short period of time.

Frequently fixing the cylinders will get the drift rate back to an acceptable level.

My understanding is that, if there is significant loader drift it can NOT be due to just the cylinders. Even if fluid is leaking through the cylinders, the loader wouldn't drift unless fluid also passes through the control valve. So the control valve is the issue; cylinders may or may not also be an issue. In a thread I started this summer, I was asking about trying to isolate the issue to the cylinders vs the control valve, but was told that no matter what the control valve is the problem: https://www.tractorbynet.com/forums/hydraulics/397731-how-can-i-test-loader.html.

I have to say, after that discussion I'm still perplexed as to how I'd know the cylinder seals are faulty. Last weekend I turned off the tractor with the loader 1/2 up and watched it slowly sink to the ground. But a few minutes later I picked up a 800lb log no problem. I will also mention that on occasion, the loader will act funky for a second. Sometimes when under heavy load, the loader will go up for a quick second when your asking it to go down (or vice versa). This doesn't happen all that often but perhaps is an indication of a cylinder vs valve issue.

 

[oldnslo]

4lane
You are correct the valve must leak for the cylinder to drift in the retract mode.

What is the big unknown is how much the increase in valve leakage is when the cylinder piston seals allow leakage which then pressurizes both ends of the cylinder and consequently both the raise and lower ports on the valve.

Testing the cylinders is typically far easier and less costly than replacing the valve and still having a problem.

A simple non invasive cylinder test.

Support the loader on a jack.

Unplug only the blind end hose on the lift cylinder. Remove the jack. If the loader drifts the piston seals are leaking and this leakage is going across the directional valve. Fixing the cylinders stops this leak path.

 

[4lane]

4lane
You are correct the valve must leak for the cylinder to drift in the retract mode.

What is the big unknown is how much the increase in valve leakage is when the cylinder piston seals allow leakage which then pressurizes both ends of the cylinder and consequently both the raise and lower ports on the valve.

Testing the cylinders is typically far easier and less costly than replacing the valve and still having a problem.

A simple non invasive cylinder test.

Support the loader on a jack.

Unplug only the blind end hose on the lift cylinder. Remove the jack. If the loader drifts the piston seals are leaking and this leakage is going across the directional valve. Fixing the cylinders stops this leak path.

OK! And by "blind end hose" on the lift cylinder, you mean #1 or #2?

 

[oldnslo]

#2 hose is the blind or cap end of your lift cylinder. This will not tell you which cylinder is leaking but will tell you that at least one of them is leaking.

The situation where the loader will raise when valve is first moved to lower also indicates bad piston seals. Reason for this is that if the spool is opening the pressure to lower port slightly sooner than the tank to return oil connections. This pressurizes both ends of the cylinder putting it in regenerative mode.

 

[4lane]

#2 hose is the blind or cap end of your lift cylinder. This will not tell you which cylinder is leaking but will tell you that at least one of them is leaking.

The situation where the loader will raise when valve is first moved to lower also indicates bad piston seals. Reason for this is that if the spool is opening the pressure to lower port slightly sooner than the tank to return oil connections. This pressurizes both ends of the cylinder putting it in regenerative mode.

Loving this discussion and soaking in your knowledge. Much thanks for your responses. I'm excited to try this test this weekend.

I'd love to know more about how cylinder piston seal leakage leads to an increase in valve leakage. If the cylinder seals leak, then both ends of the cylinder are pressurized putting pressure on both the raise/lower ports on the valve. When seals are not leaking, just one end of the cylinder is pressurized and only one valve port is under pressure. Valve ports will inherently pass a small amount of fluid through and when one valve port is under pressure, this amount of leak is within expected thresholds. But when BOTH valve ports are under pressure (by either one cylinder or even both cylinders), there is twice the amount of valve leakage? Is that generally the idea?

 

[oldnslo]

Loving this discussion and soaking in your knowledge. Much thanks for your responses. I'm excited to try this test this weekend.

I'd love to know more about how cylinder piston seal leakage leads to an increase in valve leakage. If the cylinder seals leak, then both ends of the cylinder are pressurized putting pressure on both the raise/lower ports on the valve. When seals are not leaking, just one end of the cylinder is pressurized and only one valve port is under pressure. Valve ports will inherently pass a small amount of fluid through and when one valve port is under pressure, this amount of leak is within expected thresholds. But when BOTH valve ports are under pressure (by either one cylinder or even both cylinders), there is twice the amount of valve leakage? Is that generally the idea?

Yes both ports under pressure effectively doubles the leakage potential.

Another possible test with all of the hoses connected to see if the seals are bad enough is to fully raise the loader and then hold the valve in the raise position for minute or two. Then check the rod end hoses of the lift cylinders to see if they get warm. Leaking seals will by-pass oil, by-passing oil under pressure creates heat. Might need an infrared heat gun to check heat difference between the cylinder ports Vs using your hand.

good luck and please let us know what you find during your testing.

 

[K5lwq]

4lane,
I agree with oldnslo. He did a great job explaining the concept. The link below is a video showing another test you can do to determine which cylinder or cylinders are the issue.

Bypass testing a hydraulic cylinder - YouTube

 

[TX mower]

.... I have to say, after that discussion I'm still perplexed as to how I'd know the cylinder seals are faulty. ...

Perhaps of interest:

TESTING A DOUBLE ACTING HYDRAULIC CYLINDER (pdf file)

Describing a series of diagnostic tests that can be done with cylinders installed / in-situ (from this page on K&E Technical, Inc. website)

 

[4lane]

Agreed that this is a good first step. As others have noted in the past, there is a loopholes to oldnslo's test. Namely that the valve has to have some leaking (at least per spec) in order to make any determination on whether the cylinders seals are leaking or not. That is an assumption we're making here. So.. only one of two things is going to happen when you remove the jack from under the loader; it will drop or it won't.

1) If loader doesn't drop, then...
a) valve doesn't leak, cylinders don't leak
b) valve doesn't leak, cylinders do leak

2) If loader does drop, then...
c) valve leaks, cylinders leak


If #1 happens, great, I will have eliminated the valve as the issue. But, we're going on the assumption that the valve leaks a little (at least per spec) so #2 is the scenario we're looking for.

Keep me honest here, this is what I'm thinking...

 

[oldnslo]

Your thinking is correct 4lane

My money is on option 2

 

[LouNY]

One simple way to check for cylinder piston seal leaks is to retract the cylinder(s) all the way, remove the hose(s) from the base of the cylinder(s) and try to retract it/them more if oil flows out the cylinder port under pressure the piston seal is leaking.
If you wish to know how much put a hose on it to a container, maintain pressure for 10 seconds measure the fluid volume displaced multiply by 6 that is the flow rate of the leak at that pressure per minute.

 

[4lane]

This weekend I did OldnSlo's test. The loader did drop, about 1in/30sec - the same drop rate as when using the loader normally. So, my conclusion is:

• The piston seals WERE leaking, because the oil had a path to return to the tank since the rod end hose was connected
• If the piston seals were not leaking and the control valve was leaking, the loader would not have dropped in this test since the cap end hose was disconnected/blocked off.

Is that correct? I've proven that the piston seals are leaking regardless of if the control valve is leaking or not?

 

[K5lwq]

4lane,

You are correct. If you fix the cylinders, you might be satisfied with the internal valve leakage.

 

[oldnslo]

This weekend I did OldnSlo's test. The loader did drop, about 1in/30sec - the same drop rate as when using the loader normally. So, my conclusion is:

• The piston seals WERE leaking, because the oil had a path to return to the tank since the rod end hose was connected
• If the piston seals were not leaking and the control valve was leaking, the loader would not have dropped in this test since the cap end hose was disconnected/blocked off.

Is that correct? I've proven that the piston seals are leaking regardless of if the control valve is leaking or not?

4lane
I greatly appreciate you posting your test results.

You have proven that the piston seals and rod end port of the valve leaks. If the valve did not leak the cylinder would not drift.

This proves that the leak path through the rod end valve port is definitely contributing to the loader drift.

 

[4lane]

4lane
I greatly appreciate you posting your test results.

You have proven that the piston seals and rod end port of the valve leaks. If the valve did not leak the cylinder would not drift.

This proves that the leak path through the rod end valve port is definitely contributing to the loader drift.

Thank you again for all your insights. I'm going to post these results to the June thread on this topic since it was solely focused on this issue.