SOLVED: Hydraulic Issue on Kubota L4200

[jman31]

Hi,

First time post. I bartered for an L4200 GST 4wd that was in pieces. From my reading I guess it's somewhere from a '94-'99 model I have reassembled everything and have run into a problem. Nothing hydraulic works. The rear lift arm doesn't move and the steering does absolutely nothing. The tractor will move back and forth. The bucket attachment is off at the moment and when I press the end of the quick release hose, there is no pressure there.

I added 10 gallons of Kubota UDT2 oil and changed the hydraulic filter, but no change. I cracked the hi-pressure banjo bolt on the pump and oil came out, but it didn't seem to be under pressure.

Any advice on where to go from here would be greatly appreciated!

EDIT: Upon further inspection, there doesn't seem to be any oil in the low pressure hose that goes into the pump. There was definitely oil in the filter housing when I changed the filter if that helps any. I ran a smaller hose into the low pressure hose and there was oil in the bottom of the hose. It's just not getting up to the pump.

Jeremy

 

[TheOldHokie]

Hi,

First time post. I bartered for an L4200 GST 4wd that was in pieces. From my reading I guess it's somewhere from a '94-'99 model I have reassembled everything and have run into a problem. Nothing hydraulic works. The rear lift arm doesn't move and the steering does absolutely nothing. The tractor will move back and forth. The bucket attachment is off at the moment and when I press the end of the quick release hose, there is no pressure there.

I added 10 gallons of Kubota UDT2 oil and changed the hydraulic filter, but no change. I cracked the hi-pressure banjo bolt on the pump and oil came out, but it didn't seem to be under pressure.

Any advice on where to go from here would be greatly appreciated!

EDIT: Upon further inspection, there doesn't seem to be any oil in the low pressure hose that goes into the pump. There was definitely oil in the filter housing when I changed the filter if that helps any. I ran a smaller hose into the low pressure hose and there was oil in the bottom of the hose. It's just not getting up to the pump.

Jeremy

No oil in the suction side hose seems pretty definitive. Either the pump is not producing vacuum or there is a vacuum leak in the supply line.

Dan

 

[jman31]

No oil in the suction side hose seems pretty definitive. Either the pump is not producing vacuum or there is a vacuum leak in the supply line.

Dan

Thanks for the reply! I'm very new to hydraulics so please bear with me. Is there a way to test the pump to see if it's functioning? I don't see any leaks on the supply side, although I'm not sure how to test for that either.

 

[TheOldHokie]

Thanks for the reply! I'm very new to hydraulics so please bear with me. Is there a way to test the pump to see if it's functioning? I don't see any leaks on the supply side, although I'm not sure how to test for that either.

Given the history of the machine I would start by testing suction at the pump. Remove hose #100, start tractor, and place finger over pump inlet to see if its producing suction. If not squirt a tbsp of oil into inlet and see if that brings up a vacuum.

Dan

 

[jman31]

Tha

Given the history of the machine I would start by testing suction at the pump. Remove hose #100, start tractor, and place finger over pump inlet to see if its producing suction. If not squirt a tbsp of oil into inlet and see if that brings up a vacuum.

Dan

Thanks again for the advice. Initially it didn't have suction, but it did have suction once I added a little fluid. I'm assuming that suggests an air leak in the supply side?

 

[TheOldHokie]

Tha


Thanks again for the advice. Initially it didn't have suction, but it did have suction once I added a little fluid. I'm assuming that suggests an air leak in the supply side?

No - the pump was dry and could not prime itself. Add a little more oil while its apart then hook the suction side up and restart the tractor to see what you get.

Dan

 

[jman31]

No - the pump was dry and could not prime itself. Add a little more oil while its apart then hook the suction side up and restart the tractor to see what you get.

Dan

I did that. No luck sadly. I added enough to the pump that it started to run back out. I'll try it again.

 

[TheOldHokie]

I did that. No luck sadly. I added enough to the pump that it started to run back out. I'll try it again.

If you are getting suction at the pump it should pull oil in, Try sticking the end of hose #70 in a jar of clean hydraulic fluid and see if the pump will suck it up. Also do the finger check for suction at the end of hose #70.

Whoops! I just realized #70 is hard line but you get the idea.

Dan

 

[jman31]

If you are getting suction at the pump it should pull oil in, Try sticking the end of hose #70 in a jar of clean hydraulic fluid and see if the pump will suck it up. Also do the finger check for suction at the end of hose #70.

Whoops! I just realized #70 is hard line but you get the idea.

Dan

Man, thanks so much for sticking with me on this! I think we've verified it's not the pump. It sucked a quart down in seconds. I blew some air down the suction side and it didn't seem to have any blockage. Any advice for checking the suction side of things?

 

[TheOldHokie]

Man, thanks so much for sticking with me on this! I think we've verified it's not the pump. It sucked a quart down in seconds. I blew some air down the suction side and it didn't seem to have any blockage. Any advice for checking the suction side of things?

Just basic trouble shooting znd thats good news.

What part of the suction side plumbing did you stick in the jar?

Dan

 

[jman31]

Just basic trouble shooting znd thats good news.

What part of the suction side plumbing did you stick in the jar?

Dan

I took a pvc pipe and put it in the end of the rubber hose that goes into the pump. I stuck the pvc pipe in a bucket of oil. So I haven't verified anything beyond the rubber hose. Visually everything looks good and I know I have good flow from the case to the filter. I also checked the hard pipe that comes out of the filter and it had oil in the bottom of it. I can only surmise that the hard pipe may have a hole in it although I don't hear anything and I may not have any idea what I'm talking about.

 

[TheOldHokie]

I took a pvc pipe and put it in the end of the rubber hose that goes into the pump. I stuck the pvc pipe in a bucket of oil. So I haven't verified anything beyond the rubber hose. Visually everything looks good and I know I have good flow from the case to the filter. I also checked the hard pipe that comes out of the filter and it had oil in the bottom of it. I can only surmise that the hard pipe may have a hole in it although I don't hear anything and I may not have any idea what I'm talking about.

The pipe has an oring seal to the filter base. That oring would be my first suspect.

Dan

 

[jman31]

The pipe has an oring seal to the filter base. That oring would be my first suspect.

Dan

OK. I'll check it.

 

[jman31]

The pipe has an oring seal to the filter base. That oring would be my first suspect.

Dan

I replaced the o-ring but to no avail. The pipe does have a rubbed spot in it that could have a pinhole but everything else looks good. I thank you for your time today! I have to go to an event with the wife so I'm done for today, but at least you've given me a direction to look. I really appreciate your time!!! I'm super glad to know it's not the pump.

Regards,
Jeremy

 

[jman31]

The pipe has an oring seal to the filter base. That oring would be my first suspect.

Dan

So after more testing I think maybe the pump is bad. I got a full 5 gallon bucket of hydraulic oil and ran the suction tube into it. I ran the tractor with it sucking directly from the bucket for about 3 gallons. There was absolutely no movement of the steering or the PTO lift arms and there is no pressure on the hoses that would go to the front end loader. Does that suggest a bad pump? Other issues?

I'm wondering if I'm better off trying to just buy a new pump at $1400 or send it off to get it rebuilt? If rebuilt any suggestions on where to send it?

Jeremy

 

[TheOldHokie]

So after more testing I think maybe the pump is bad. I got a full 5 gallon bucket of hydraulic oil and ran the suction tube into it. I ran the tractor with it sucking directly from the bucket for about 3 gallons. There was absolutely no movement of the steering or the PTO lift arms and there is no pressure on the hoses that would go to the front end loader. Does that suggest a bad pump? Other issues?

I'm wondering if I'm better off trying to just buy a new pump at $1400 or send it off to get it rebuilt? If rebuilt any suggestions on where to send it?

Jeremy

If it draws oil from the bucket it should draw oil from the filter. Thats not the pump.

How did you determine there was no pressure on the loader supply hose? Do you understand the operation of the sekector valve on the hydraulic outlet block? On that tractor pressure testing the pump is very easy.

Dan

 

[jman31]

If it draws oil from the bucket it should draw oil from the filter. Thats not the pump.

How did you determine there was no pressure on the loader supply hose? Do you understand the operation of the sekector valve on the hydraulic outlet block? On that tractor pressure testing the pump is very easy.

Dan

OK. That's good to know. I have been studying into the pressure relief valve as possibility, but no, I'm not familiar with selector valve. I will look it up. Get back shortly once I brush up so I can have a semi understanding of what we're talking about.

For the loader, I just pressed the little bump on the end of the hose to open it. A friend of mine said you shouldn't be able to push it in if it's got pressure. No air or fluid comes our when it's running.

J

 

[TheOldHokie]

OK. That's good to know. I have been studying into the pressure relief valve as possibility, but no, I'm not familiar with selector valve. I will look it up. Get back shortly once I brush up so I can have a semi understanding of what we're talking about.

For the loader, I just pressed the little bump on the end of the hose to open it. A friend of mine said you shouldn't be able to push it in if it's got pressure. No air or fluid comes our when it's running.

J

If the pump is sucking oil in it has to go out. You need to make sure the selector on the outlet block is in the loader position and familiarize yourself with the three hoses that connect the loader to the block.

Dan

 

[jman31]

If the pump is sucking oil in it has to go out. You need to make sure the selector on the outlet block is in the loader position and familiarize yourself with the three hoses that connect the loader to the block.

Dan

Ok. I have no idea how or where the selector on the outlet block is or the outlet block, and all my research has just confused me. it's not just the loader that doesn't work. It's the steering and the PTO lift. It's like all of the oil is getting diverted straight back to the case and none is reaching any of the cylinders.

 

[North Idaho Wolfman]

I bartered for an L4200 GST 4wd that was in pieces. From my reading I guess it's somewhere from a '94-'99 model I have reassembled everything and have run into a problem.

I'm wondering if this is the root of your problem.
Was the hydraulic pump off the engine when you got it?
To what extent was it disassembled?