Can the hydraulic system get air locked after a fluid change

[RayIN]

Look. Let's back up & try to unconfuse things a bit. The problem is the OP has done a hydraulic oil and filter change and now his hydraulic pump is not moving fluid. So in his original question in the title of this thread the he asks,

"Can the hydraulic system get air locked after a fluid change"​

The answer is that in an open center hydraulic system like his Kioti and most small tractors use, the hydraulic system cannot get air locked because it is not a sealed system. The sump is always open to the atmosphere by way of the vented sump. Hydraulic fluid cannot get "air locked" because one end of the circulation is open to the atmosphere. Any air gets moved along - or not - to the sump and escapes to the atmosphere. That's not to say that there can't be trapped air in the system causing other effects, but it won't cause an "air lock".
An "Air Lock" is not why his pump isn't working.

BTW, the radiator and cooling system are different.
Modern tractor cooling systems ARE SEALED SYSTEMs. They are not open to the atmosphere unless the system overheats. They definitely do have to be purged of air during filling because once the radiator cap is tightened down that system is sealed. It is not open to the atmosphere, so with the radiator cap in place there is no way for air to escape. In a sealed cooling system a trapped air pocket doesn't always mean the entire flow is blocked, but it can be. It will create a "hot spot". So there definitely are ways that an air lock can cause heating problems in a sealed system.

Hope this helps,
rScotty

I read his first post as the HST pump is the problem.
Another on my list of why I won't buy a tractor with HST.

 

[Leonard malone]

Trouble shooting section

 

[ptsg]

Leonard, can you give us a recap on what are exactly the issues you're experiencing? The thread got slightly all over the place, so there is probably more confusion now than before.

 

[Leonard malone]

The tractor will move forward and reversefor a short distance and then it is like it is in neutral. Rocking foot pedal back and forth a couple times and it will move again.there is a noise like a stomach growling and then it starts to move.

 

[Leonard malone]

Today I removed wheels,fenders,floor boards etc to be able to get a better look. I found the pressure test ports and relief valves. Ordered a hydraulic pressure tester from amazon.I also found a couple of things I wasn't aware of. A small leak in the remote hydraulics but only when they are activated. The tractor has a form of cruise control and the lever to activate it does nothing.where the linkage enters the housing seems to be seized.I don't know if this could have anything to do with the problem.Any input much appreciated.Thanks,Len

 

[rScotty]

Today I removed wheels,fenders,floor boards etc to be able to get a better look. I found the pressure test ports and relief valves. Ordered a hydraulic pressure tester from amazon.I also found a couple of things I wasn't aware of. A small leak in the remote hydraulics but only when they are activated. The tractor has a form of cruise control and the lever to activate it does nothing.where the linkage enters the housing seems to be seized.I don't know if this could have anything to do with the problem.Any input much appreciated.Thanks,Len

Not at all unusual for remotes to leak when they are activated. The problem is when they are activated one of the remote hoses holds pressure - but without a remote implement there is no pathway for fluid back to the sump. A leak there doesn't mean a problem. Try working the control lever for the remote while the engine is off. Sometimes that will release trapped pressure. Or look up hydraulic coupler pressure relief tools. Some just use a light tap wit a hammer and a rag on the coupler end.

I don't know exactly how that linkage to the cruise control works on yours. but it sure sounds suspicious. I'd definitely work on that and get it right. That could be the problem.

By the way, congratulations on removing parts and also getting a set of guages ordered. We can use another hydraulics guy on TBN.
rScotty

 

[Leonard malone]

Thanks Scotty ,I'm supposed to get gauges by Saturday.I'll keep you posted. The cruise control linkage is mechanical I'll fix it but not sure it could contribute to my problem?

 

[Leonard malone]

The leak in the remote tube was at the but not the coupler. I tightened it and stopped that leak. The main hydraulic filter seems to be leaking very slightly. I cleaned it completely and checked it after a couple hours and it was wet.

 

[rScotty]

Thanks Scotty ,I'm supposed to get gauges by Saturday.I'll keep you posted. The cruise control linkage is mechanical I'll fix it but not sure it could contribute to my problem?

I'm not sure either. But at least it is in the right system. What did you ever figure out on the Kioti clutch? Does it have one? If so, can it be locked or adjusted?

 

[Leonard malone]

Yes it has one a clutch pedal.

 

[Leonard malone]

Fingers crossed !!!! I think i found the problem. I noticed a very small leak,more of a weep . The connection where the tube from charge pump joins the filter housing. I replaced the O ring and it stopped . Ran the tractor in forward and reverse no problem.( Up on blocks) seemed smooth and no growl or whining. Putting it back together now to try it outside.I'll let you know how it goes.

 

[rScotty]

Fingers crossed !!!! I think i found the problem. I noticed a very small leak,more of a weep . The connection where the tube from charge pump joins the filter housing. I replaced the O ring and it stopped . Ran the tractor in forward and reverse no problem.( Up on blocks) seemed smooth and no growl or whining. Putting it back together now to try it outside.I'll let you know how it goes.

That's wonderful. We sure covered a lot of ground. Would you have found it without removing "wheels,fenders,floor boards etc"?
You should probably put "RESOLVED" onto the Thread title. BTW, What do you think was the cause of the leak?
rScotty

 

[arrow]

You should probably put "RESOLVED" onto the Thread title.
rScotty

Not yet.
Too many things seem to get haunted with premature jubilation.
He takes his machine outside, moves like it should and then I’ll say hurray.
It’s been a great thread nonetheless.

 

[rScotty]

Not yet.
Too many things seem to get haunted with premature jubilation.
He takes his machine outside, moves like it should and then I’ll say hurray.
It’s been a great thread nonetheless.

You are absolutely right. Better to wait.

And something that puzzles me is Len says, "The connection where the tube from charge pump joins the filter housing".
What puzzles me is the charge pump is not very accessible - most people don't even know it exists. It only services the HST, and lives back by the HST tranny rather than on the side of the engine. Also, that pipe from the charge pump is under positive pressure so any leak from it to the HST FILTER should be more than a weep; I'd expect a spray.

I wonder if Len is referring to a suction leak in the pipe that joins the MAIN HYDRAULIC filter to the main hydraulic pump?
rScotty

 

[arrow]

You are absolutely right. Better to wait.

And something that puzzles me is Len says, "The connection where the tube from charge pump joins the filter housing".
What puzzles me is the charge pump is not very accessible - most people don't even know it exists. It only services the HST, and lives back by the HST tranny rather than on the side of the engine. Also, that pipe from the charge pump is under positive pressure so any leak from it to the HST FILTER should be more than a weep; I'd expect a spray.

I wonder if Len is referring to a suction leak in the pipe that joins the MAIN HYDRAULIC filter to the main hydraulic pump?
rScotty

I was thinking the same thing. It could have been hemorrhaging this entire time and only looks like a leak when pressure is shut down.
He has the schematics which should label the pieces so he may be calling it right.
I give the guy credit for tearing into it at any rate.

As far as location, by his description, it seems he is spotting it at the filter housing base which should be quite visible.
I just hope it’s a fix for Len whatever type of leak it w@s.

 

[Leonard malone]

Sorry guys it's the tube from hydraulic filter housing to the section of the transmission where the charge pump is located.your right you can't see the charge pump .The schematic says this tube is under charge pressure as oppos to high pressure. It's now 4:55 am and I'm about to pull her outside to try it.

 

[Leonard malone]

This is the leak

 

[Leonard malone]

9:35 pm just spent an hour clearing snow! It's working fine now. Thanks to you guys and your input. It gave me encouragement to look deeper into the problem. Not to mention the $ you saved me.Feels good to know at 65 I am still learning. Thanks Len

 

[rScotty]

Sorry guys it's the tube from hydraulic filter housing to the section of the transmission where the charge pump is located.your right you can't see the charge pump .The schematic says this tube is under charge pressure as oppos to high pressure. It's now 4:55 am and I'm about to pull her outside to try it.

This is the leak

Sorry right back. That looks like a suction leak to me. What say, arrow?

 

[rScotty]

9:35 pm just spent an hour clearing snow! It's working fine now. Thanks to you guys and your input. It gave me encouragement to look deeper into the problem. Not to mention the $ you saved me.Feels good to know at 65 I am still learning. Thanks Len

You are welcome. Glad it worked.