Hydraulics fail when tractor warms up?

[autocol]

Hi Guys,

I'm new to this site, and new to fixing tractors. I'd usually search the forums for an existing answer more vigorously than I have, but I don't really know what anything on the tractor is called, so I don't know what to search for!

Anyway, hopefully you fine fella's can help me out.

I have a little old Kubota tractor, with a front end loader. When you first start the tractor the bucket will raise and lower correctly, but it's a bit slower than it should be, and sort of "jumpy". If you let the tractor warm up, the hydraulics get to the point where they barely work, if at all.

Now, if I understand correctly the hydraulic oil is shared with the gearbox? (I think I remember my dad, the original owner of this little tractor, saying that... but he's been dead for 12 years so the memories are hazy!). Does this mean the oil is getting too thin and therefore not working properly? Would changing all the oil potentially fix the problem? Or does it mean a valve is leaking somewhere maybe?

I don't really know where to start looking, or what to look for. I'm a decent home mechanic, but I have no experience or knowledge about hydraulics.

Oh, and the oil is the same stuff that was in there when my dad died, so it's at least 12 years old - and knowing my dad he may not have changed it for 10 years prior to that either!! :laughing: If changing the oil is the first port of call, what do I ask for?

Any help or advice you could offer would be great.

 

[J_J]

Go ahead and change out the fluid, and install a hyd gage in the system, and check the pressure. Read your manual, or call the dealer and find out what the pressure should be.

Move the the 3pt lever about midway, and see if there is any difference.

 

[Mechanos]

Do as JJ suggesested... but in addition to just changing the oil, make sure you remove and clean the strainer and also install a new hydraulic oil filter.

 

[mmurphy]

If you post model of Kubota you have, some one may even be able to help more with other info about tractor.

 

[brain55]

Also post what model it is. "Little old Kubota" doesn't narrow it down much. The loader model would help too. It will help us point you in the right direction if you are unsure of where the suction screen or filters are. Change the hydraulic oil and clean the suction screen it needs to be done anyway. My bet is that you won't notice much of a change, it could help with the hydraulics feeling jumpy though. The next step would be to have a flow test done on the hydraulic pump. A pressure test by itself will not tell the whole story, you will need to know how the pump flow is affected by the pressure, you can have pressure and no flow. From the description you gave, I would just about bet that your hydraulic pump is worn out. That is why I do a flow test first, to confirm or eliminate that possibility. You can waste a lot of time checking other things and it still be the hydraulic pump.

Brian

 

[Egon]

Is the tractor HST or is it gear/clutch unit?

Can you tell where the hydraulic pump is mounted?

Is the pump internal or external?

Does it have reservoir tank?

 

[wdchyd]

Also post what model it is. "Little old Kubota" doesn't narrow it down much. The loader model would help too. It will help us point you in the right direction if you are unsure of where the suction screen or filters are. Change the hydraulic oil and clean the suction screen it needs to be done anyway. My bet is that you won't notice much of a change, it could help with the hydraulics feeling jumpy though. The next step would be to have a flow test done on the hydraulic pump. A pressure test by itself will not tell the whole story, you will need to know how the pump flow is affected by the pressure, you can have pressure and no flow. From the description you gave, I would just about bet that your hydraulic pump is worn out. That is why I do a flow test first, to confirm or eliminate that possibility. You can waste a lot of time checking other things and it still be the hydraulic pump.

Brian

.......:thumbsup:.......My thoughts exactly

 

[autocol]

Hi Guys, thanks for all the help!

Okay, I'll do my best to answer the questions you've got:

First, the tractor is a Kubota B6100.

The loader doesn't have a model number that I can find, just a Kubota stamp. If it makes any difference, it also has a grader blade on the back that powers upwards hydraulically (down is just gravity powered I think), and it demonstrates the same issues (slow and jumpy when cold, almost completely inactive once warm).

Is the tractor HST or is it gear/clutch unit?
Well, I don't actually know what HST means, but it certainly has a mechanical gearbox if that's what you mean.

Can you tell where the hydraulic pump is mounted?
I'm pretty sure it's on the right hand side of the engine, under the exhaust manifold and behind the fuel pump.

Is the pump internal or external?
External, I think. I wouldn't take that as gospel though because I'm only fairly sure that what I'm lookin at is the pump! It's about the size of a petrol V8 starter motor. It's got a decent size "hard line" down to the bottom of the gearbox which I assume is the pickup.

Does it have reservoir tank?
I can't see a reservoir, though the whole pump is fairly obscured by the exhaust and the shroud around the engine.

This ad listing features a tractor that looks pretty much identical to mine, and the specs it lists (engine size and horsepower) all match what's written on the plate on mine. It's also the only image I could find on the web which shows a loader that looks like mine. All the others I found look slightly different.

Again, thanks very much fellas. I really appreciate your help.

Col.

 

[Egon]

As per J_J and mechano. Also check the oil level before draining.:thumbsup:

 

[jinman]

Col. it appears to me that you know so little about this tractor that you would be far better off to take it to a Kubota dealer's shop and have them look at it. While there, also see about ordering an Operator's Manual and read it thoroughly. When it comes to tractors, you just can't beat a good knowledge of how things work and what the maintenance points are. Rather than take a chance of making the situation worse, why don't you get it looked at by experts and spend your time and money well on becoming more familiar with your tractor? I have an idea you are going to say that the shop will be expensive, but in my experience, nothing is more expensive than doing the wrong thing. Give yourself some time to learn and next time you may be able to take care of the problem yourself.:thumbsup:

 

[brain55]

The hydraulic pump is on the right hand side of the engine as you are sitting on the seat, and the hard line running back to the gear box is the suction line. Where that line goes into the gear box is also where the suction screen is located. When you change the hydraulic oil you will want to pull that screen out and clean it also. One last question to confirm that your loader is being operated off the main pump and not an auxillary pump off the front of the engine, which was common on the older B6100's. On top of the hydraulic pump on the side of the engine, there is also a steel line coming off the top of the pump running to the back of the tractor. Right in front and above the brake pedals there could be an aluminum block with two hydraulic hoses going to the loader valve, if you have this then you only have the one hydraulic pump, which I am pretty sure is what you will find. When you are changing the hydraulic/transmission oil there is more than one drain plug, there will be the one at the bottom of the mid-pto case and there will also be one on each rear axle reduction case, you want to pull all three of these plugs to drain all of the fluid. You will want to refill it with Universal Tractor Hydraulic Fluid. I'm assuming the since you used the term "petrol" you are not in the US so I won't be much help telling you where you can find the oil. I am still pretty convinced that your hydraulic pump is worn out, especially since the 3-pt is showing the same symptoms.

Brian

 

[JohninCT]

The below thread may be of help to you.

http://www.tractorbynet.com/forums/kubota-owning-operating/67415-kubota-b6100-hydraulic-issue.html

This place will email you a parts diagram that might also help you
Kubota B6100 Parts

Like others have said, getting an owners manual for the tractor would be a wise investment.

 

[autocol]

Hey guys, fantastic help, thank you!

Jim, honestly I'm under no illusions as to how much of this repair I can take on myself, but before I take it to a dealer and spend $500 plus, I'd rather change the oil and clean up filters/screens myself, to see if it's worth the effort. Especially seeing as both front tyres and toast and require replacement. I'm trying to ascertain whether I can get this tractor back in working condition for a reasonable sum, or buy a better condition unit second hand. Sentimental attachment says I would prefer the former

Brian, thanks heaps for your descriptions, I'll go and have a look now and see what I see. You correctly surmise that the US of A is not my location (though I have lived in Eugene OR for a time), because I'm an Aussie.

I think I'll change the oil and clean the screen, and see what happens. I'll come back and let you know what happens

 

[autocol]

Brian I went and had a look, as you guessed there's a block just in front of the brake pedals which has a couple of soft lines heading up to the loader valve.

I spoke to my Dad's best mate as well and he remembers thinking there was something amiss in the loader valve block. For a minute there I was excited to think I might have narrowed down the problem without doing any work :thumbsup: ... but then I realised that the rear 3PT exhibits the same symptoms so it couldn't be that, could it?

Or, would a leaking valve in the loader valve block potentially cause a pressure reduction in the whole system? I'd love it to be the valve block. Getting at the pump looks like a "remove the exhaust manifold" job, and by the looks of things that would mean "remove all the broken studs along the way"!! This old girl has spend some time out in the weather

I've ordered a workshop manual so hopefully that will start to shed some light too.

 

[brain55]

You can eliminate the possibility of it being the loader valve by bypassing it. Take one of the hydraulic hoses by the brake pedals and loop it from one fitting to the other so the loader valve won't be in the system, if the 3-point still operates the same you know the problem is not in the loader valve. If the 3-point functions properly then it is in the loader valve, likely the relief valve. If it is the hydraulic pump it is really not that tough of a job. You wouldn't need to remove the intake manifold, just the fuel filter assembly and the 2 steel hydraulic lines. Kubota uses plated bolts so they would have to be very corroded to have issues with them breaking.

Brian

 

[autocol]

Brian, you're a gun. I'll test the bypass and report back. Love your work

 

[autocol]

G'day Brian (and any other interested onlookers),

I finally got around to trying the bypass today (I'm moving house so it's all a bit chaotic at the moment).

It confirmed what you suspected Brian, which is that the hydraulic pump is probably shot. The 3PT exhibited all the same mis-behaviours as it did when plumbed through the loader valve.

A couple of questions before I go and buy and new pump:

1. What should the hydraulic oil look like? I'd describe the stuff that came out as an opaque creamy colour (with some dirty patches too).

2. How much oil should there be? I had to take off both hoses leading to the aluminium block and replace them with one I borrowed from the front of the loader in order to get a hose with the right size threads at both ends. None of the hoses appeared to be "full" of oil when I took them off, which wasn't what I expected. I would have thought that a correctly operating system would be absolutely full to the brim with oil? Like bleeding the brake line in a car, I can't imagine air in the system helping!

If it's possible that the tractor just needs a good drain and refill - how do know how much to put in, and is there some kind of trick to refilling the system and bleeding the air out? Should I be trying this before buying a new pump?

Thanks again for your help

Col.

 

[J_J]

I would definitely drain the milky fluid. It apparently has water in it. That in itself will cause poor performance. After you drain the fluid, then work all the hydraulic functions through the motions and the air should purge itself.

 

[Steve_Miller]

Was there another relief besides the loader relief valve on those tractors? I had one 15 years ago but can't remember.

Steve

 

[autocol]

I'm slowly progressing on my little tractor fellas.

Firstly, the manual I bought on eBay has arrived which has helped a bit - though unfortunately I could only find a DVD version so I have to keep coming back inside to refer to it.

However, I've now drained all the fluid (which I'm sure would have HORRIFIED you blokes), and pulled out the suction screen filter at the base of the sump which has - I suspect - highlighted the problem. The screen was nearly covered in little black chunks of what used to be a seal. I can be certain it used to be a seal, in fact, because I managed to fish a decent sized slice of it out with my finger.

So, I'd say that makes it a very good chance that if I find out where that seal is from, I'll solve my problem. So... um... how do I do that!? If a slice half an inch long managed to find it's way to the suction screen, does that give us a clue, or could it have been dragged there from anywhere in the system?

So, to put my current questions in point form:

1. Other than refilling the hydraulic oil, is there something else I can/should flush through there to get the major crap out?
2. What steps should I take to try to find my missing seal?

Thanks.
Col.