Kubota L3830D Hydraulic Issue - Low Pressure

[22West]

Greetings Folks,

Long term reader but first time poster. I’m hoping to get some help troubleshooting a low pressure hydraulic issue on my Kubota L3830D tractor. I apologies about the long post, but I hope this is detailed enough for feedback and also helpful for future readers.

The issue seems to be that the hydraulic system on the tractor will not create enough pressure to operate the FEL.
I recently added a Westendorf FEL to the tractor. After the install and doing the final hose connections (following the manufactures guidelines), I raised and lowered the bucket a few times successfully to test the loader out. After 4-5 reps the loader suddenly stopped raising the bucket at all and would only lower. The bucket will now only curl, but at a rate that can only be described in inches per minute. The only functions I have on the FEL are the ones that gravity helps with.

Thus began my saga of troubleshooting:
At first I thought that the hydraulic system was low on fluid since the hoses were dry when I installed them and I lost a little bit of fluid when installing the new connection block on the tractors front hydraulic connection block. Got some Kubota UDT2 fluid and topped it off. No change.

Thinking I had connected some of the hoses incorrectly, I went back to the FEL hydraulic install instructions and even looked up the L3800 service manual to verify that the right hoses were in the right place. Everything is connected correctly, still no joy.

Next I ordered a hydraulic pressure gauge test set. To eliminate the new FEL as an issue, I disconnected the FEL lines and connected a test gauge directly to the ‘pressure out’ port on the tractors front hydraulic connection block. That’s when I discovered that the system has very low pressure. At idle I have 50-75psi, at 1000rpm I have 100psi, and at 2000rpm I have 600psi. The most I have seen is about 800psi when operating the 3pt to max height to trip the pressure relief valve for the rear cylinders. The service manual says the system should create aprox 2500psi at 2700rpm. Even with math not being my strongest subject, this seems like an issue.

Additionally I have replace the hydraulic fluid filter in case there was a clog causing insufficient fluid to reach the pump. I have also taken out and cleaned the pressure relief valve located on the front hydraulic connection block in case there was debris casing the valve to stick open.
Interestingly enough the power steering seems unaffected and the 3pt in the read raises and lowers with the same speed it has in years past.

Any help on troubleshooting would be appreciated. I am fairly mechanically inclined, but new to the hydraulics on this tractor. Not sure what to test next. After looking ove the tractor and the service manual, there doesn’t seem like much left other than the hydraulic pump itself. Could the pump be bad/worn out with only around 500 hrs on it? How would you test this?

 

[JWR]

Do not guarantee that my observations will solve anything for you but here goes...

• It depends a lot on where you took the pressure measurements. Your hydraulic pump on the tractor is either putting out 2000 psi or better or it is not. See if you can get a measurement at or near the pump.
• If the pump is not putting out 2000 psi ballpark then you know the pump is your problem. Even with such low hours we have no way of knowing what it has been though or how it may have been damaged. [How long have you had the tractor? Buy it new or used?] To my knowledge many, if not most, medium sized utility tractors have a separate pump for power steering and some do for the 3pt hitch/lift. If the same pump on yours drives both steering AND auxiliary hydraulics then it probably has a mechanism to give priority to steering for obvious reasons. I have heard that configuration exists.
• I think the fact that the loader worked OK initially (at least for a while) is key information on the problem. I am GUESSING that probably means there is foreign matter/junk [or air] somewhere in the lines. Could be debris that got in during your connection chore. Could be something that was in the lines or the loader valve or ?? before you made the connections. Seems to me it worked until the debris reached a valve or an orifice somewhere in the chain. Right now I lean towards air.
• It is possible it is something as simple as that the lines all need to be bled !? Air in the lines SHOULD be something you can get rid of by repeated cycling of the controls [many times with the engine in mid range rpm] but maybe not. Westendorf should be able to give you verbal assist on how to bleed the lines.
• Where did you get the loader valve? Part of the Westendorf loader kit? I can't see your setup nor make an intelligent suggestion without more info but you should be able to use your gage set to isolate the problem. Many loader valve mfrs are willing to talk on the phone and help debug issues (I have done that with a different manufacture of a loader valve.)
• Do you have "remotes" at the rear of the tractor? They would be driven by the same main hydraulic pump as the loader. Try one of those with any hydraulic device handy or borrowed and see if that is working well.

Start by bleeding the system and making sure no air pockets remain. Just too many things to chase without more info. Hope some of this helps.

 

[22West]

JWR, thanks for taking the time to reply. Let me try to answer some of your questions.

-I am taking the pressure measurement from the forward hydraulic connection block. This is the next item in line from the pump itself. For this system, hydraulic fluid is drawn from the transmission case, through a filter, and then into the pump. The pump is a gear driven tandem pump with a common shaft. The first pump powers the main hydraulic circuit (FEL ports, rear 3pt). The second pump feeds the power steering and PTO clutch.
From the pump the main hydraulic circuit is piped to a distribution block under the tractor. That block has a pressure relief valve and then connection points for the FEL and 3pt hydraulic lines. For troubleshooting I have disconnected the FEL lines and connected the pressure gauge directly to this connection block. The is the first spot to 'tap' in after the pump and pressure relief valve.

-The fact that I get such low pressure makes me think the pump has failed. I am the second owner of this tractor, but it was previously owned my grandfather who was know for being easy on equipment. He only used it to cut tall grass in the fields. Of course damage to the pump could have happened at any time, but seems like the addition of the FEL is the main suspect.

-I have thought about there being debris in the system. That prompted me to change the fluid filter and check the relief valve for junk. The service manual doesn't show any other filters or screens in the system. I wonder if debris in the lines from my initial hookup/install got caught in the pump vanes and has damaged the pump to where it can't build pressure. Without taking the pump apart I'm not sure of any other way to tell.
I had assumed the air in the FEL lines would bleed out with cycling the FEL some. I had not thought about there being air in the main hydraulic circuit. I was under the assumption that in an open circuit hydraulic system the air would work its way out as fluid flows through the system.

Thanks for the suggestions. I am going to continue to do some troubleshooting to look for other obvious issues before ordering a replacement pump.

 

[Dave M7040]

Almost always a plumbing error.

Do not take the pump apart as you will create greater problems. The clearances in modern pumps are beyond the tools and ability of most mechanics.

Your hydraulic pressure will always be low on an Open Center system until the flow is restricted so your test can be very misleading.

Power Beyond connections need to be completely understood. I suspect this is where your poor performance and low pressure are coming from.

Dave M7040

 

[JWR]

JWR, thanks for taking the time to reply. Let me try to answer some of your questions.

-I am taking the pressure measurement from the forward hydraulic connection block. This is the next item in line from the pump itself. For this system, hydraulic fluid is drawn from the transmission case, through a filter, and then into the pump. The pump is a gear driven tandem pump with a common shaft. The first pump powers the main hydraulic circuit (FEL ports, rear 3pt). The second pump feeds the power steering and PTO clutch.
From the pump the main hydraulic circuit is piped to a distribution block under the tractor. That block has a pressure relief valve and then connection points for the FEL and 3pt hydraulic lines. For troubleshooting I have disconnected the FEL lines and connected the pressure gauge directly to this connection block. The is the first spot to 'tap' in after the pump and pressure relief valve.

-The fact that I get such low pressure makes me think the pump has failed. I am the second owner of this tractor, but it was previously owned my grandfather who was know for being easy on equipment. He only used it to cut tall grass in the fields. Of course damage to the pump could have happened at any time, but seems like the addition of the FEL is the main suspect.

-I have thought about there being debris in the system. That prompted me to change the fluid filter and check the relief valve for junk. The service manual doesn't show any other filters or screens in the system. I wonder if debris in the lines from my initial hookup/install got caught in the pump vanes and has damaged the pump to where it can't build pressure. Without taking the pump apart I'm not sure of any other way to tell.
I had assumed the air in the FEL lines would bleed out with cycling the FEL some. I had not thought about there being air in the main hydraulic circuit. I was under the assumption that in an open circuit hydraulic system the air would work its way out as fluid flows through the system.

Thanks for the suggestions. I am going to continue to do some troubleshooting to look for other obvious issues before ordering a replacement pump.

Outstanding response and added detail! You and I are thinking pretty much the same on this. Since you are measuring pressure at the port you described , I would have thought you should have full pump pressure up to the setting of the relief valve there. However, Dave M7040 is more experienced than myself and I'd go by what he says. Based on what Dave said I do not see where you would measure to get representative pressure -- I suppose at the outlet of the loader valve headed for the FEL cylinders ? That would make a great data point of evidence anyway.

If you have a plumbing diagram of how you are hooked up (the one you presumably followed from the FEL manufacturer) the involvement of the power beyond circuit (or whether yours involves power beyond) should be visible. I do not know how the loader could have worked OK 4 or 5 cycles and then suddenly quit if it is a plumbing connection mistake.

For whatever it is worth, if it really comes to that -- and it may not -- my cousin has an elderly Oliver tractor with high hours on it and he was able to get a local shop to rebuild the hydraulic pump for him for far less money than a new pump would cost.

Repeating my curiosity -- do you have a remote for hydraulic attachments in back?

 

[rScotty]

SNIP
From the pump the main hydraulic circuit is piped to a distribution block under the tractor. That block has a pressure relief valve and then connection points for the FEL and 3pt hydraulic lines. For troubleshooting I have disconnected the FEL lines and connected the pressure gauge directly to this connection block. The is the first spot to 'tap' in after the pump and pressure relief valve.

-The fact that I get such low pressure makes me think the pump has failed. I am the second owner of this tractor, but it was previously owned my grandfather who was know for being easy on equipment. He only used it to cut tall grass in the fields. Of course damage to the pump could have happened at any time, but seems like the addition of the FEL is the main suspect.

-I have thought about there being debris in the system. That prompted me to change the fluid filter and check the relief valve for junk. The service manual doesn't show any other filters or screens in the system. I wonder if debris in the lines from my initial hookup/install got caught in the pump vanes and has damaged the pump to where it can't build pressure. Without taking the pump apart I'm not sure of any other way to tell.
I had assumed the air in the FEL lines would bleed out with cycling the FEL some. I had not thought about there being air in the main hydraulic circuit. I was under the assumption that in an open circuit hydraulic system the air would work its way out as fluid flows through the system.

Thanks for the suggestions. I am going to continue to do some troubleshooting to look for other obvious issues before ordering a replacement pump.

I was surprised when reading your post that the low pressure at the output of the made you think the pump had failed. If I had hooked it up as your describe with the pressure gauge on the distribution block and seen that low of a pressure, my first thought would be that the relief valve had failed and was wide open. My second thought would be that the hydraulic pump had a suction leak and was being starved for fluid.

It would help to have a hydraulic schematic. But without one we can make some progress just assuming that yours is a typical open circuit system.
Does the 3pt hitch work normally for both lifting speed and power? If so, then the problem cannot be the relief valve, the hydraulic pump, or the suction feed to the hydraulic pump.
But depending on which side of the distribution block the gauge is on, it might still be a defect within the distribution block.

Diverter blocks rarely go bad, but it could happen.
There are two types of distribution blocks that are commonly used = fixed and adjustable.
The fixed block regulates flow by having different diameter internal drillings. Pretty much bulletproof.

The adjustable type is actually one of two types. One has an simple valve inside adjusted on the outside via a screw adjustment and lock nut....., and the other type has the same screw and locknut, but it is called a "proportional type" and instead of a valve you are adjusting a spring that controls the proportion of flow going to either the FEL or 3pt 50/50 or 30/70 etc..... in such a way that no matter how much or little the flow (flow is roughly linear with RPM) the proportion sent to each side stays the same.

To test the distribuition block, you could simply plumb around the distribution block if you don't trust it.
See if the FEL or 3pt work then. BUT IF YOU PLUMB AROUND IT YOU MUST PROVIDE RELIEF VALVING AND A LOW RESISTANCE HIGH FLOW PATH TO RETURN FLUID TO THE SUMP FROM THE RELIEF VALVE.

BTW, this is a good time to mention that I don't block off the flow when I use a pressure gauge, my guage is a "T" with quick connects on each end and the gauge in the middle. That way I can watch it as the implement is used. Although a hydraulic pump can be deadheaded if the relief valve is functioning, the temperature will rise quickly. I learn more connecting via a T. One of the things you learn is that most loader functions take place at much lower pressure than the system is capable of. My system mostly runs between maybe 20 and 900 psi. By studying the gauge I can get a pretty good guess as to how my system is operating. What I cannot tell of course is if it is not flowing at all....

Not being able to distinguish between no flow and no pressure is a conundrum. Someday I hope to own or build a real hydraulic flow stand that will give simultaneous flow rate and pressure readings. Then all sorts of diagnostics become simple. Most tractor dealer shops DO NOT have such a hydraulic flow stand - which is sort of like an electrical guy doing diagnosis without a VOM.

So bottom line is check the 3pt hitch before going any farther. And consider making up a $50 dollar pressure gauge with a T and either quick disconnects if your system already has them, or add them, or just use normal hydraulic threaded connections. YOU MUST USE HYDRAULIC RATED COMPONENTS. DO NOT USE PLUMBING FITTINGS. You can leave that gauge in the system indefinitely...mine is mounted to the loader directional control valve. Although some glycerine-filled pressure gauges will freeze in cold weather it hasn't hurt mine.

What else... Oh, you asked about air in the system. Air means almost nothing in an open hydraulic system. It will work its way out pretty quickly. Vented via the sump vent. You'll probably never notice it after the first minute or so... and not much even them. After all, pneumatic systems work pretty well and they are entirely air....
Hope I haven't missed anything simple here...
rScotty

 

[22West]

Thanks everyone for your input. I am on the road today, but will try post some pictures of my lines/connections and a diagram of the tractor hydraulic system soon.
I have been learning quite a lot about hydraulic systems, power beyond, and flow/pressure over the last week of troubleshooting. I appreciate folks willingness to chime in with advice.

 

[rScotty]

If you need some cheap entertainment - a few years back "Fluid Power World" published some tutorials on hydraulic systems. The series began with how to read hydraulic schematics.
Recommended.

This old link might still get you there:

Hydraulic symbology 101: Understanding basic fluid power schematics - Fluid Power World

By Josh Cosford, Contributing Editor Out of any topic under the patio-sized umbrella of fluid power, hydraulic symbology garners the most requests from those wishing to learn more about fluid power. Reading any schematic with more than three symbols can be daunting if your experience is limited...

www.fluidpowerworld.com

rScotty

 

[22West]

rScotty, that was a very helpful link. I pulled up my tractors hydraulic system diagram from the service manual and was looking through it as I was reading about the different symbols.

I will try to post some pictures tomorrow of the diagram and my setup.

 

[Dave M7040]

rScotty, that was a very helpful link. I pulled up my tractors hydraulic system diagram from the service manual and was looking through it as I was reading about the different symbols.

I will try to post some pictures tomorrow of the diagram and my setup.

The type of transmission will result in different hydraulic circuits.
What type is yours? Manual, Glide Shift or hydrostatic
How many hoses connect to your new loader valve...... 6 or 7?
Dave M7040