# L4150 dilemma, return circuit



## John S. (Jun 19, 2018)

Greetings all,
Wonder if anyone can help with a mid eighties kubota l4150 with backhoe (pro driven) and loader mounted, and shuttle shift tranny. Both the loader and transmission only engage intermittently every four minutes or so and only for a second or two. I'm pretty sure it's the return loop clogged with deteriorated brake material and wonder if there's a way to blow that circuit back for a temporary fix. I have tried pressurizing the tranny case with no luck. Also tried sucking out from the filter boss with no luck. There is no return screen on this machine. Maybe there is a guru of sorts around these here parts that might get me back up and running. Any and all help with this would be greatly appreciated for the fact that I'm just plain stumped as to what to do other than split the machine.
Thanx in advance.
John S.


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## RC Wells (Dec 26, 2008)

Sounds like the hydraulic filter and the magnetic filter under it are the culprit. The filter is on the suction side of the pump and the slightest blockage creates problems. When the filter is removed, if it has the the magnetic filter, it also must be removed, cleaned, and then reinstalled. 

Also, if the filter is not properly installed, it will suck air and cause the system to air lock.

If it is not a filter issue it will likely be the hydraulic pump.


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## John S. (Jun 19, 2018)

Thanks for the reply RC.there is no magnetic filter on this machine. I failed to mention in original post that last time I changed the filter for this problem I did in fact get brake material out and also just moments ago pulled the filter and fished a wire around the return port which dislodged some (a very small amount) of the crud enough to get flow of oil out into the catch pan and allow the loader and shuttle to operate properly so I'm 99 percent convinced it's clogged there and that's causing the issue.
The filter thing you mentioned I'm sure isn't it.
Any other thoughts would be a godsend and thanx again for the prompt reply.


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## RC Wells (Dec 26, 2008)

Sounds suspiciously like the pump, but check the line from the filter to the pump first.

Move up the hydraulic line (out of the transmission housing in front of the filter, and runs to the pump) to the rubber hose. If it is soft, loose, or wet it may be likely culprit. They develop air leaks, and the smallest amount of crud in the filter will result in oil cavitation and hydraulic starvation. There are also a couple O rings to check, one on the connection of the suction pipe below the filter, and the other on the connection block on top of the pump.

One thing I recommend on the L series that does not have the magnetic filter unit, is to score a wrap around filter magnet for the outside of the hydraulic filter. It will keep minute damaging metal particles out of the pump. Amazon or Ebay usually has those magnets for reasonable prices.


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## John S. (Jun 19, 2018)

RC,
The line from filter to pump is clear and sound, no air inclusion whatsoever in the circuit.
As I mentioned in the previous post I do know where the blockage is but don't know how to clear it short of splitting the machine. I'm hoping someone will chime in with a trick to do so. I've wiggled a wire around the return ports with some results but I'd like to get it all cleared out somehow. I've tried pressurizing the case with no results, I wish I knew what fitting to grab onto with either air pressure or fluid flow to reverse the blockage. I'm going to try and rig up a suction hose small enough to get into the return port and see what that produces for now, hopefully someone who's "been there done that" (apparently these machines are notorious for consuming their own brake linings) will offer up a way in which to get this done.
Thanx for the suggestions as well.
Regards,
John S.


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## sixbales (May 18, 2011)

Howdy John, welcome to the tractor forum.

You might try blowing out the inlet port to the filter. Take the filler cap off of your hydraulic reservoir so you don't blow a seal somewhere. Wrap a rag around your air gun tip to confine the air.

When the tractor has sat idle for a few hours, does it work OK for a short period??


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## John S. (Jun 19, 2018)

Six thanks for the reply,
Before todays wiggling a wire around the return port on the trans casting( after taking the filter off to access it) the issue was constant. Now both loader and trans. Work as they should but I know it's only a matter of time before it happens again. The reservoir for the loader is the transmission (it runs off the tractors internal pump, hence both loader and shuttle shift failing in tandem) and I did in fact block the tranny breather off and pressurize the dipstick hole (more convenient because of its size relating to a standard rubber tipped air gun) with no results. I was thinking it might do the trick as well but no. 
When I pull the filter there is the post that the filter screws to in the center which enters the tranny sump and then there is a cast in opening below that which shares the return line from the pump so the fluid comes from the pump, enters the casting galley,shared by that cast in opening mentioned above exits that opening to circulate through all the little perimeter holes in the filter to pass through the filter elements and enter the tranny sump through the center post. Hope you can follow that. So I'm not sure how that brake material could get where it is because it seems to me it would have to get through the filter first which would be impossible for the size of the debris being anywhere up to eight inch in size.
Regardless I need to clear it out of course so keep your thinking cap on if you would, I certainly appreciate the help.
Thanx again for all your replys !!


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## John S. (Jun 19, 2018)

To all,
This pic shows cast in port I'm referring to. The hard hydraulic line boss with the three bolt boss fitting comes directly from the pump return and I believe shares the same cast in port within the filter boss confines. I'm also under the impression the center dumps into the sump after the fluid circulates through the filter, maybe I'm wrong but I've done my homework as to how a filter works and all I'm seeing on the net pertaining to filter info tells me this. Hope this clears things up a bit.
Thanx to all in advance!!


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## rhino (Jan 9, 2017)

Your tractor is 4 wheel drive, remove the drop gear case to it and that might give you a good place to flush the transmission out. This may help


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## RC Wells (Dec 26, 2008)

The L series with the spin on hydraulic filter has no internal serviceable screen, all debris is captured in the filter. There was a hydraulic sump kit update for some of the L4150 models equipped with loaders. What that consists of is an extended oil sump pick up tube and a shorter dipstick that allows for two more gallons of oil. You may want to check with your dealer to see if yours was in that group, and then overfill it by two gallons of UTF..

I think rhino is on to a temporary solution if you have a disintegrated hydraulic shuttle clutch, where the fiber linings have clogged the intake sump. However if that is the case you are probably flowing so much oil to the failed shuttle clutches that the pump will not keep up with the flow.


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## John S. (Jun 19, 2018)

Rhino thanx for the reply,
Yes it is four wheel drive, when you say drop gear case you mean the transfer case or what?
Not sure but will take a look at the parts book for that term.
RC thanx again, no extra sump option, prior to this issue with the "brake lining material" clogging things up the tractor was a champ through thick and thin, no issues at all,ran and moved strong,always kept the level at the sticks marks. 
I've looked at the schematics of the tranny but it's hard to tell what's going on behind that filter boss so I'm poking around blind in there, wish I knew the path the oil takes after the filter so I can get behind the crud and dislodge it all. I'll keep at it, hope others might chime in with a sure fix.
Thanx again to you all for your knowledge and patience.
JKS


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## RC Wells (Dec 26, 2008)

The case being referred to is the Front Wheel Drive case, located under the transmission and is the output for the front drive Propeller Shaft. Drain the transmission and then drop that case and most of the crud will come out of the transmission with some flushing.

The hydraulic sump update is a longer pickup tube and short dipstick. The tube is internal to the transmission case. Most Kubota dealers will have a registry of the serial number of the machines which have been updated with the sump update.

When you blow back through the filter housing through the three smaller holes at the bottom, you are clearing the sump tube. If you have a lot of material in the sump, it will immediately suck back onto the tube you just cleared.

I recommend you go to Kubota's website and drill down to the parts diagrams for your version of the tractor. Take a look at the transmission case diagram. The rear PTO section can be removed allowing access inside the housing, and the use of a pneumatic solvent gun will allow you to blow crap out of the case and down through the drain plugs and the hole for the removed Front Wheel Drive Case.

Also take a look at the slide for the second shaft of the hydraulic shuttle, if you have the hydraulic shuttle. Those clutches are the most frequent source of material in the hydraulic system, and why the hydraulic oil is changed at the recommended interval.


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## John S. (Jun 19, 2018)

RC, great to hear from you,
Good stuff!!! Maybe a combination of the transfer case(thanx rhino!), pto and speed change cover removal along with blowing out the sump to get the crud on the floor of the case and flushing and solvent and yada yada yada will get me somewhere. I have the parts book for the machine so it's all coming together visually for me.
This machine does in fact have the hydraulic shuttle shift and you mention the clutch material as most likely culprit so I would ask, if the shift lever works as promised and the machine pulls strong forward and reverse could it still be the clutches or no? I know brake lining and clutch lining are if not very similar then the same in texture and color, is there a way to tell with a piece in hand where it came from? Maybe a test or three of sorts to determine which system has broken down?
The brakes feel fine btw. 
Thanx for your knowledge and patience RC, and rhino and six and anyone else who happens by.
JKS


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## RC Wells (Dec 26, 2008)

Short of pulling a rear axle trumpet and cleaning the case, there is no reliable means to check the brake condition.

The shuttle clutches are designed to shed material out into the transmission sump. So plenty of that stuff will be inside on the bottom of the sump. The brakes not so much. They shed inside the trumpets, and the material usually is dissolved and suspended in the oil. Big chunks generally lodge inside the trumpet next to the transmission case.

If all is good to go once the crud is out of the system, I would leave well enough alone until you hit around 7,000 hours or detect poor performance.

One of the issues I face with my hydraulic shuttle tractors is operators that run the hand throttle at rated speed, then shift on the fly. The foot throttle is what you use with a hydraulic shuttle, then release the throttle and come to a full stop before changing directions. Shift, bring the RPMs up and go the other direction. The shuttle clutch is mechanically similar to the automatic transmission clutch packs in an automobile, and you do not jerk them into gear with the engine racing either.

Some tractor sales guys will claim the shuttle can be shifted on the fly and at rated RPM, but not true if you want your tractor to last a very long time.


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