L2350 Hydraulic Pump Seal Leaking/ Failure

KenVen · Feb 25, 2015

I have a L2350 (bought used) that lost all hydo fluid into my crank. Searching forums looks like a bad seal. I replaced the seal, however still same problem. The mech at the Kubota shop said sometimes they don't hold and pump replacement is needed. Looks like the pump has been off before based on condition of the bolts. Also the main input rigid fluid line to the pump was cut probably for some maintenance and spliced with hose and clamps. Noticed bubbles in hydraulic fluid prior to losing it all out the breather tube.

Can air be getting into pump from spliced line causing seal to fail? Is seal failing a common occurrence on Kubota pump? Replacement of the pump is expensive and my concern is that the new pump might blow the seal if something is causing failure other than an old pump seal. Because it looks to have been worked on before in the same area I am thinking seals fail but other posts seem to indicate something is causing the seal to fail. Any ideas?

North Idaho Wolfman · Feb 25, 2015

First the "cut line" is not cut it's made that way.
Yea a bad hose/clamps can cause it to suck air but that won't blow the seal.
Was just the center of the seal (sealing lip) blown out or was the whole seal?
Was the snap ring in place?
Has anyone added any pressure lines, like for rear remotes or loader?

If you replaced the seal and it blew out right away then yes your either going to have to get another, or have that one rebuilt.
Normally the cause of the seal blowing is bypassing hydraulic fluid due to worn parts inside the pump, so yes replacing or rebuilding the pump will fix it.
New P/N 31351-76102 $458.35
http://www.colemanequip.com/parts/KubotaParts/31351-76102/

But a good hydraulic shop should be able to rebuild yours and probably for much cheaper.

The other cause (Very much a long shot) could be a stuck bypass regulator that is causing it to build too much pressure, you can remove the valve and check for any trash or restriction in the valve, clean it and replace every component in the same order or it will not work.

Pump lines:

Pressure regulator valve:

KenVen · Feb 25, 2015

Yea I found that schematic on Messicks after I posted and realize the hose is suppose to link the two pieces of rigid line. The seal looked OK and the lock ring was in place. I replaced a hose on the front loader about a month before. I will check the valve, thanks for replying.

BadDog · Feb 25, 2015

Just a thought, but was it working ok before, and has anything changed? In other words, could it be dead-heading and causing it to blow out? Particularly if a relief is stuck or restricted as mentioned by NIW?

KenVen · Feb 26, 2015

All that is different is the new hose on the bucket. when I replaced the hose the loader was working fine until the loss of all the hydraulic fluid / mixed oil out the breather hose. Prior to the oil dump I lost power steering, clutch was hard to engage and bucket became very slow to operate. I presume all due to the loss of hydraulic fluid and the excess fluid in the engine also caused compression and power to fall quite rapidly.

I am unfamiliar if a simple hose connection or if the hose somehow caused a fluid flow issue could in turn cause the seal to leak.

North Idaho Wolfman · Feb 26, 2015

KenVen said:
I am unfamiliar if a simple hose connection or if the hose somehow caused a fluid flow issue could in turn cause the seal to leak.

If the hose was a feed or return and was causing a restriction it could cause issues like blowing a seal, in your case that's not the issue.

Where are the FEL lines (feed and return) hooked too?
Are the hooked up to a plate just under the seat on the right?

KenVen · Feb 26, 2015

Stay tuned for that reply. Tractor is down at my ranch and I am here in the big city. Next trip out there I will post an update.

North Idaho Wolfman · Feb 26, 2015

KenVen said:
Stay tuned for that reply. Tractor is down at my ranch and I am here in the big city. Next trip out there I will post an update.

Take some pictures of the connection and such if you can too.

KenVen · Apr 27, 2015

Wolfman I think you are still in the lead for best reason all my fluid is exiting through the pump seal. I just purchased the shop manual since I am still having the problem after replacing the seal and then replacing the pump. Pressure has to be released somewhere and the seal is the weakest point.

The manual describes the purpose of the pressure relief valve you had me check as to "when the pressure in the circuit rises the valve will open to allow fluid to return to the transmission case to relieve pressure." I don't think this valve is operating correctly, not opening, therefore building too much pressure and blowing the pump seal. (I am getting a good schooling in hydraulics.) The spring should compress allowing space between the poppet and the seat. When I took apart the valve only the spring came out not the poppet or anything else in your diagram.

I will take it apart again and see if I can get the poppet removed as well. Not sure how I will remove the poppet if it is stuck inside the chamber perhaps with some fine pointed tool to pry and poke it lose.

Any ideas on that would be welcome. I know the problem is not difficult to solve but one needs a thorough understanding of tractor hydraulics to resolve. To date I have only needed an operator's manual to maintain my Kubota not a Shop Manual and only a knowledge of operating my tractor not needed to know how hydraulics work to run it.

01jordyn · Oct 25, 2015

I have a Kubota L2350 with a front loader. Yesterday I started to use the front loader and it wouldn't lift well and the hydraulic system was whining. I thought maybe it had air in the system but it never changed. Does anyone know if it would have a filter on the hydraulic system. Or can someone tell me what they think the problem might be?

motmow · Oct 25, 2015

01jordyn said:
I have a Kubota L2350 with a front loader. Yesterday I started to use the front loader and it wouldn't lift well and the hydraulic system was whining. I thought maybe it had air in the system but it never changed. Does anyone know if it would have a filter on the hydraulic system. Or can someone tell me what they think the problem might be?

You should start a new thread, but the L2350 has a mesh screen in the bottom of transmission case. It should be behind the supply line (big line) that goes to the hydraulic pump. Are you low on fluid? Whining usually means the pump is starving for fluid. If fluid level is good, pull that line (you're gonna lose all your fluid) pull that screen filter and clean with kerosene or solvent.

John Trucker · May 4, 2024

I am having a similar problem with my 30yr old L2350DT. The oil pan overflowed with hydraulic fluid. I totally rebuilt the hydraulic pump, replacing every seal in the pump and connecting lines. I could see the rupture in the seal in one spot along the shaft. I used the tractor mildly afterwards and it was fine. I started lifting heaving loads of dirt again and after a couple of hours of intense use a few quarts leaked into the crank. Am I just pushing this tractor too hard or is there a problem in another part. In the above posts, it mentions cleaning the relief valve. I have never had any lift problems or chatter. Can this componant cause an over pressure problem?
I am using the tractor to load sandy loam from a wash near the ranch. I have to really drive the bucket in low to fill the bucket sometimes. This is not the most powerful tractor for that kind of work. Just wondering if I'm overdoing it.

TheOldHokie · May 4, 2024

John Trucker said:
I am having a similar problem with my 30yr old L2350DT. The oil pan overflowed with hydraulic fluid. I totally rebuilt the hydraulic pump, replacing every seal in the pump and connecting lines. I could see the rupture in the seal in one spot along the shaft. I used the tractor mildly afterwards and it was fine. I started lifting heaving loads of dirt again and after a couple of hours of intense use a few quarts leaked into the crank. Am I just pushing this tractor too hard or is there a problem in another part. In the above posts, it mentions cleaning the relief valve. I have never had any lift problems or chatter. Can this componant cause an over pressure problem?
I am using the tractor to load sandy loam from a wash near the ranch. I have to really drive the bucket in low to fill the bucket sometimes. This is not the most powerful tractor for that kind of work. Just wondering if I'm overdoing it.

My guess is your pump is worn beyond fixing.

If worried about the relief you can easily check he system pressure to make sure it is not too high. I doubt that is teh problem, The usual failure is too low not too high.

John Trucker · May 8, 2024

TheOldHokie said:
My guess is your pump is worn beyond fixing.

If worried about the relief you can easily check he system pressure to make sure it is not too high. I doubt that is teh problem, The usual failure is too low not too high.

Thanks. When the pump wares out, what causes the overpressure? Or is it just a possible wobble in the shaft causing the oil seal to breach?

TheOldHokie · May 8, 2024

John Trucker said:
Thanks. When the pump wares out, what causes the overpressure? Or is it just a possible wobble in the shaft causing the oil seal to breach?

The shaft seal is not designed to handle full pump hydraulic pressure. Those pressures are contained by the wear plates and seals inside the pump. When the internal parts in the pump wear the shaft seal is exposed to the higher pressures that start leaking past the sealing surfaces inside the pump.

The other issue is shaft wear. Over time the shaft wears at the sealing surface and starts to leak. Thats easier to see when you remove the old seal.

Given the history you mightvwant to price a new pump.

Dan

John Trucker · May 8, 2024

TheOldHokie said:
The shaft seal is not designed to handle full pump hydraulic pressure. Those pressures are contained by the wear plates and seals inside the pump. When the internal parts in the pump wear the shaft seal is exposed to the higher pressures that start leaking past the sealing surfaces inside the pump.

The other issue is shaft wear. Over time the shaft wears at the sealing surface and starts to leak. Thats easier to see when you remove the old seal.

Given the history you mightvwant to price a new pump.

Dan

Thanks Dan. The new Kabota pump is over $1K and I wanted to confirm the problem. I won't purchase the cheap China pumps. I want another 30 years out of it.

North Idaho Wolfman · May 8, 2024

John Trucker said:
Thanks Dan. The new Kabota pump is over $1K and I wanted to confirm the problem. I won't purchase the cheap China pumps. I want another 30 years out of it.

If you buy a Kabota pump, I'm going to guarantee you that it's a cheap china knock off.
Now if you buy a Kubota pump, then you might do better.

TheOldHokie · May 8, 2024

North Idaho Wolfman said:
If you buy a Kabota pump, I'm going to guarantee you that it's a cheap china knock off.
Now if you buy a Kubota pump, then you might do better.

I will guarantee that for 10X the price I would not even consider a genuine Kubota pump.

Dan

North Idaho Wolfman · May 8, 2024

TheOldHokie said:
I will guarantee that for 10X the price I would not even consider a genuine Kubota pump.

Dan

Yea but would you do a KABOTA pump?

L2350 Hydraulic Pump Seal Leaking/ Failure

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