B26 tlb hydraulic issues

[smallorange]

Since there appears to be quite a few instances of this problem on the forums can you expand on that a bit more, with regards which bushing and why? Just wondering if the front seal on this pump is not up to the job, and allowing air in over time, allowing wear to front bush, or whether the front bush is poor and wearing causing movement in the shaft which in turn allows air in past the seal?

What happens is the pump is mounted on the engine and turned by the timing gear, and there is about a 3/4'' steel line running from the pump to the oil tank, it is connected to a rubber elbow with two spring clamps, this is the suction side. In colder weather the cheaper grade oil will be like molasses in the line. As the engine and pump warms up the hot oil that was in the pump on start up gets pumped out. Because the oil in the suction line is so thick, the pump can't suck the oil up, therefor your pump is running without lubrication wearing out the brass bushings in the pump. (I think there brass haven't pulled mine apart yet) So once the bushings are worn the shaft wobbles and sucks in air. This all happens in about 10 minutes. The tolerances in a hydraulic pump are so tight that any bit of wear makes a huge difference. So even if you have a heater on your tank like I did, you still run the risks of burning up your pump. The Kubota oil is specially formulated for cold operation, and it does not thicken up, they already figured all that out for you and they know not everybody lives where its warm. I have also been told that as the tractor ages the rubber elbow attaching the line to the pump develops cracks in it and possibly suck air in. I spoke with 3 different Kubota mechanics and they all told me the same thing better stick with Kubota oil in a Kubota, other equipment it doesn't seem to matter as much. I learned all this the hard way, in spite of being a mechanic myself.

 

[CurtisC]

smallorange,
Good to know, given my circumstances if its the pump I'd guess I'm not as far along as you were but headed that way. Just curious, looking at the parts manual there's 8 bushings - a front and rear pair on fwd (main output) chamber and front and rear pair on power steering output. Were just some of the bushings gone or were they all bad? I haven't checked with dealer, but do they sell a rebuild kit at least for the seal and soft goods or did you have to by each part individually?

 

[100 td]

Thanks smallorange,
While I don't have a B26 (B21) I have a few problems I'm trying to sort, but am genuinely interested in the outcome and will be awaiting the pics of your pump pulled apart! (I think I may order new seals and bushes for my own pump as a general maintenance item) Also of course it's great for others in the future to be able to search for similar info which actually leads to a resolution.
However, I'm wondering if the bushings are wearing prematurely and then allowing the seal to be worn and allow air in, then at very low temps or after filter change with a filter full of air it exacerbates the problem leading to further failure.
And as you had a heater, I suspect it was not to do with the viscosity of the oil, the seal was already leaking.
How many hours on your machine?

 

[100 td]

CurtisC,
If it were me, I would replace all bushes, side plates, rings and seals in both sections of the pump. I'll have to get around to doing that on mine, only single pump though. From the quick look at parts prices(for mine at least), very cheap in the scheme of things. Hopefully smallorange will post detailed pics of his pump when pulled apart.

 

[CurtisC]

CurtisC,
If it were me, I would replace all bushes, side plates, rings and seals in both sections of the pump. I'll have to get around to doing that on mine, only single pump though. From the quick look at parts prices(for mine at least), very cheap in the scheme of things. Hopefully smallorange will post detailed pics of his pump when pulled apart.

Agreed, pump rebuild also a good time to replace the 90 deg. suction hose. Performance is still good as long as its not too cold out so its just a question of when. Using smallorange's logic (which makes sense) its a slippery slope when you have pump wear and cold weather combined.
I saw smallorange talk about a tank heater - North Carolina mountain winters are usually not that harsh but there are cold days and a tank heater sounds like good insurance to future problems (waiting for a pump that doesn't like cold oil to warm it up seems counterproductive). It looks like the type that bonds to bottom of the tank is about the only way to go - anyone got any input on best approach for the B26? Total oil capacity is about 7 gal. if memory serves.

 

[100 td]

I don't know what temps you get down to, but if you put a 4 quart container of oil in the freezer over night and you can pour the oil out of in it the morning then you know your oil is OK down to 0F at least. I'd say premature wear in the front bush allowing the front seal to suck air is probably a bigger problem, and I'd hazard a guess that this is the actual underlying cause of the problem. (smallorange has 2400 hrs on his)
Don't let me dissuade you from a heater though, it certainly cant hurt.

 

[CurtisC]

I don't know what temps you get down to, but if you put a 4 quart container of oil in the freezer over night and you can pour the oil out of in it the morning then you know your oil is OK down to 0F at least. I'd say premature wear in the front bush allowing the front seal to suck air is probably a bigger problem, and I'd hazard a guess that this is the actual underlying cause of the problem. (smallorange has 2400 hrs on his)
Don't let me dissuade you from a heater though, it certainly cant hurt.

No disagreement, front seal and bushing wear seems most likely cause probably accelerated in my case by the pump being run early in its life with wrong viscosity oil (too high). Morning temperatures on days I had worst pump performance were around 10 deg. F. Warmer incoming oil on a cold morning should minimize cavitation or air intake maybe getting me through another winter before tearing the pump down. I'd also think a tank heater in cold climates along with always using the correct oil would help extend the life of a new pump. As you said it couldn't hurt.

 

[art]

Being a dealer I will they to bring across a point. I have listened to farmers who have to run a tractor or two every day come in after a cold day and say the tractor was fine but when I started it this morning I had no hydraulics. I let it run and after an hour they started working but not like normal and feeling a lack of performance. They starved the pump.
Many oil changes are spread to far because of the cold that often gets condensation in the oil during the winter. This excess moisture lays in the bottom of the oil galleries and normally where your hydraulic oil pick-up is.
As far as oils go I like some factory oils but not many! Very few generic oils have I trusted.

 

[smallorange]

Being a dealer I will they to bring across a point. I have listened to farmers who have to run a tractor or two every day come in after a cold day and say the tractor was fine but when I started it this morning I had no hydraulics. I let it run and after an hour they started working but not like normal and feeling a lack of performance. They starved the pump.
Many oil changes are spread to far because of the cold that often gets condensation in the oil during the winter. This excess moisture lays in the bottom of the oil galleries and normally where your hydraulic oil pick-up is.
As far as oils go I like some factory oils but not many! Very few generic oils have I trusted.

That's what happened to me, I starved the pump, I should have had a heater on the steel line coming from the tank, and I should have had Kubota oil in it. The Shell Spirax is a good quality oil but does not have the same viscosity as Kubota. I plan on rebuilding my pump and keeping it for a spare, for now I bought a new one.

 

[dabadas]

Be careful replacing the rubber elbow. I replaced my pump and elbow and when I would rev the engine it start making a noise. Come to find out it sucking it shut causing the pump to start cavitating and whinning. Put the old hose back on problem solved. I couldn't squeege the old one but I could the new one.