Can the hydraulic system get air locked after a fluid change

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Len
Is the pump still whining?
Is there any place close that could bench test this for you.
Alternative is to get a test kit Scotty mentioned and mount a gauge right after the pump if you have the room or an adaptor.

 

[oldnslo]

Len
Since this post in now 10 pages what is the problem you are experiencing and associated symptoms.

Is it just that the tractor will not move? If yes back to question of is the input shaft from the engine to transaxle turning when you are trying to drive the tractor? If that shaft is not turning you have a clutch problem..

 

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Len
Since this post in now 10 pages what is the problem you are experiencing and associated symptoms.

Is it just that the tractor will not move? If yes back to question of is the input shaft from the engine to transaxle turning when you are trying to drive the tractor? If that shaft is not turning you have a clutch problem..

What are you referring to as a “clutch” on an hst tractor?

 

[rScotty]

I don't know about Len's CK 25 Kioti, but some HST tractors do have a traditional clutch. So it isn't impossible - his might have a clutch.
I wouldn't have believed it either, but our M59 Kubota is a HST and it has a traditional clutch that looks like any other - left foot pedal and all. I have no idea why, but there it is.

Pushing the clutch petal down interrupts the power to the input transmission shaft just like on any manual shift - except in this case the transmission is not a manual, it is a HST.

Frankly I wish ours didn't have a foot clutch. I can't see a use for it, and having it puts both steering brakes on the right side next to the HST F/R pedal. You might think it is for the PTO, but the PTO has its own clutch.

 

[ptsg]

What are you referring to as a “clutch” on an hst tractor?

You can see the clutch on the OP's HST tractor on post #66. It's used mostly to engage/disengage the PTO.

I've wondered if the OP locked the clutch pedal down and forgot entirely about it.

 

[arrow]

You can see the clutch on the OP's HST tractor on post #66. It's used mostly to engage/disengage the PTO.

I've wondered if the OP locked the clutch pedal down and forgot entirely about it.

Or to change ranges.
All the “ clutch “ pedal is doing is operating a valve for fluid control.
There is no “disc/ pressure plate” as a real clutch would have.
A swash plate is acting to dictate flow pressure and direction but this involves pistons in a fixed or stationary plate.
Not seeing a clutch in the sense of what I know as a drive mechanism on an hst .

 

[arrow]

I don't know about Len's CK 25 Kioti, but some HST tractors do have a traditional clutch. So it isn't impossible - his might have a clutch.
I wouldn't have believed it either, but our M59 Kubota is a HST and it has a traditional clutch that looks like any other - left foot pedal and all. I have no idea why, but there it is.

Pushing the clutch petal down interrupts the power to the input transmission shaft just like on any manual shift - except in this case the transmission is not a manual, it is a HST.

Frankly I wish ours didn't have a foot clutch. I can't see a use for it, and having it puts both steering brakes on the right side next to the HST F/R pedal. You might think it is for the PTO, but the PTO has its own clutch.

Not as a drive mechanism in the traditional sense. There are some hsts that do not have a clutch pedal. There really is no need for one except it is simply cheaper to incorporate one for fluid volume control on our tractors rather than using electronic solenoids, sensors and relays.
What the clutch pedal does on an hst is to control what some call an “inching valve”..This valve is what is controlling fluid volume for specific things such as range changes or pto control.
The plungers on these valves should be all the way in.
I made mention of this adjustment previously and would be the first thing l would look at.
This tractor is almost 20 years old.
It’s gonna need stuff and the second thing l would have addressed is the pump.
There are too many things within that pump that can be compromised within 20 years.

 

[ptsg]

Or to change ranges.
All the “ clutch “ pedal is doing is operating a valve for fluid control.
There is no “disc/ pressure plate” as a real clutch would have.
A swash plate is acting to dictate flow pressure and direction but this involves pistons in a fixed or stationary plate.
Not seeing a clutch in the sense of what I know as a drive mechanism on an hst .

Yes, there is a conventional dry clutch. You can see it on post #66. It's there for the PTO. You don't really need a clutch to change ranges on an HST. Many HST tractors are like this.

I'll add a picture from the parts catalogue as well:

 

[oldnslo]

Or to change ranges.
All the “ clutch “ pedal is doing is operating a valve for fluid control.
There is no “disc/ pressure plate” as a real clutch would have.
A swash plate is acting to dictate flow pressure and direction but this involves pistons in a fixed or stationary plate.
Not seeing a clutch in the sense of what I know as a drive mechanism on an hst .

Arrow
The clutch is controlling the mechanical input from the engine to HST. It is not part of the HST transmission. On my Branson it controls the PTO like PTSG states and also disconnects all mechanical input from the engine. It also allows starting tractor without and mechanical power going to transaxle so engine turns over much easier in cold weather.

I have not seen a Kubota or Deere that have this feature but diagram posted by Len certainly looks like there is a clutch between engine and transaxle.

 

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Arrow
The clutch is controlling the mechanical input from the engine to HST. It is not part of the HST transmission. On my Branson it controls the PTO like PTSG states and also disconnects all mechanical input from the engine. It also allows starting tractor without and mechanical power going to transaxle so engine turns over much easier in cold weather.

I have not seen a Kubota or Deere that have this feature but diagram posted by Len certainly looks like there is a clutch between engine and transaxle.

What you talk about is fluid control. From what I’ve seen on my brand is an input shaft connected to the crank with gearing. If the engine is turning, so is the input shaft. If it is not, the gearing is either stripped, bearing compromised or attachment failed. The control, speed and direction of the tractor is happening after that with valve/fluid regulation.
Some even use that pedal as a brake mechanism as to disrupt fluid volume to relieve pressure. It is what makes range changes easier and also controls live ptos.
Are you the seeing the swash plate? I’ve heard that referred to as a clutch.
Why would an hst need fingers, pressure plate and clutch disc as a drive if it’s relying on regulated pressured fluid delivery to move?