3rd Function hydraulic routing?

[Alfred_2345]

Hi,

New member that recently bought a used L3901 with LA575 FEL and BH77 backhoe. I don’t have any experience with tractors but I am an electronics engineer so I have some technical background.

The previous owner had installed a Land Pride 3rd Function kit. I picked up a used SGC1060 grapple that was not originally associated with the tractor. (Hoses were longer and had wrong couplings.) I replaced the grapple hoses & couplings but the grapple won’t operate. After reviewing the workshop manuals, various YouTube videos and tracing out the hose connection to the 3rd Function valve, I believe the previous owner installed the 3rd Function incorrectly. See “Existing” picture. Port names are per the Kubota manuals.

I could not find any installation instructions or videos for 3rd function valves that include a backhoe. I tried to find any relevant posts here but the search terms are too generic. I want to hook up the 3rd Function value as shown in the “Proposed” image (uses the existing hoses in place and just changes the connections at the hydraulic block).

Will this work?

From what I have learned, FEL, BH, & 3rd Func should be “in series” (i.e. one after the other in the circuit) and order shouldn’t matter. (In the future I plan on rerouting the hoses to eliminate the elbow and one hose. That routing would place the 3rd Func. in the circuit between the FEL & BH. But I first want to get things working.)

Second question: As I don’t know the history of the grapple, I don’t know what type of hydraulic fluid is in it. Is this an issue? Do I need to drain the cylinders so I don’t contaminate the tractor hydraulic fluid?

Thanks in advance,
Alfred

 

[old and tired]

2nd diagram Looks good to me, you can not have a "T" in the high pressure (power beyond) line... Also, it's LA525, not LA575 front end loader

About draining the hydraulic fluid... how well do you think the previous owner too care of the tractor?? And how many hours before changing it again? Most of us with a new tractor will replace all the fuilds (engine oil, hydraulic oil and front axle oil) to start fresh... and know for sure. Mount the grapple, use it then change the oil...

 

[TheOldHokie]

Hi,

New member that recently bought a used L3901 with LA575 FEL and BH77 backhoe. I don’t have any experience with tractors but I am an electronics engineer so I have some technical background.

The previous owner had installed a Land Pride 3rd Function kit. I picked up a used SGC1060 grapple that was not originally associated with the tractor. (Hoses were longer and had wrong couplings.) I replaced the grapple hoses & couplings but the grapple won’t operate. After reviewing the workshop manuals, various YouTube videos and tracing out the hose connection to the 3rd Function valve, I believe the previous owner installed the 3rd Function incorrectly. See “Existing” picture. Port names are per the Kubota manuals.
View attachment 93541
I could not find any installation instructions or videos for 3rd function valves that include a backhoe. I tried to find any relevant posts here but the search terms are too generic. I want to hook up the 3rd Function value as shown in the “Proposed” image (uses the existing hoses in place and just changes the connections at the hydraulic block).
View attachment 93542
Will this work?

From what I have learned, FEL, BH, & 3rd Func should be “in series” (i.e. one after the other in the circuit) and order shouldn’t matter. (In the future I plan on rerouting the hoses to eliminate the elbow and one hose. That routing would place the 3rd Func. in the circuit between the FEL & BH. But I first want to get things working.)

Second question: As I don’t know the history of the grapple, I don’t know what type of hydraulic fluid is in it. Is this an issue? Do I need to drain the cylinders so I don’t contaminate the tractor hydraulic fluid?

Thanks in advance,
Alfred

The third function should be ahead of the backhoe. Putting the third function after the backhoe will over pressurize the tank port on the BH valve and you are risking expensive damage.

Dan

 

[Alfred_2345]

2nd diagram Looks good to me, you can not have a "T" in the high pressure (power beyond) line... Also, it's LA525, not LA575 front end loader

About draining the hydraulic fluid... how well do you think the previous owner too care of the tractor?? And how many hours before changing it again? Most of us with a new tractor will replace all the fuilds (engine oil, hydraulic oil and front axle oil) to start fresh... and know for sure. Mount the grapple, use it then change the oil...

My concern is mixing the unknown oil from the grapple cylinders into the tractor system. Is all hydraulic oil compatible?

The tractor (supposedly 2019) had a little under 450 hours when I got it. I have already changed the air filter and engine oil and plan on fuel filter next. I am still debating changing the hydraulic oil and coolant just in case the previous owner didn't.

 

[TheOldHokie]

My concern is mixing the unknown oil from the grapple cylinders into the tractor system. Is all hydraulic oil compatible?

The tractor (supposedly 2019) had a little under 450 hours when I got it. I have already changed the air filter and engine oil and plan on fuel filter next. I am still debating changing the hydraulic oil and coolant just in case the previous owner didn't.

If you are concerned just drain the cylinders. Remove both hoses and move rod in/out to purge both ends and make a nice oily mess.

Dan

 

[Alfred_2345]

The third function should be ahead of the backhoe. Putting the third function after the backhoe will over pressurize the tank port on the BH valve and you are risking expensive damage.

Dan

Thanks for the advice. I will take the time now to reroute the hoses so BH is last. I saw some generic videos/instructions placing the 3rd func. ahead of the FEL. Does it matter?

Since I am an engineer, I am always wanting to understand the systems I am working on so I can do so correctly. Can you explain why the BH needs to be last? The only thing I can see in the BH circuit diagrams is some pressure relief valves. I am guessing if the 3rd func is after the BH and blocked, these pressure relief values have nowhere to relieve to?

About the oil compatibility, I don't know how concerned I should be....
And I would rather not make a oily mess as you point out.
I had a lot of "fun" greasing everything already. Electronics sure is a lot cleaner.

 

[TheOldHokie]

Thanks for the advice. I will take the time now to reroute the hoses so BH is last. I saw some generic videos/instructions placing the 3rd func. ahead of the FEL. Does it matter?

Since I am an engineer, I am always wanting to understand the systems I am working on so I can do so correctly. Can you explain why the BH needs to be last? The only thing I can see in the BH circuit diagrams is some pressure relief valves. I am guessing if the 3rd func is after the BH and blocked, these pressure relief values have nowhere to relieve to?

About the oil compatibility, I don't know how concerned I should be....
And I would rather not make a oily mess as you point out.
I had a lot of "fun" greasing everything already. Electronics sure is a lot cleaner.

Oil compatability is not a concern but cleanliness is. I would purge them. Leave the hoses attached and use a bucket to contain the mess

The teason the BH valve needs to be last is it does not have a power beyond port. Kubota cheats and runs the tank port to the power beyond return on the hydraulic block. Then they lock the 3pt valve out which keeps the circuit open to tank effectively making it a tank port. When you put the 3rd function between the BH and the three point you are using the tank port on the backhoe to supply pressre for the 3rd function - e.g. you are using it as a power beyond port. The BH valve is not designed for that much back pressure and it damages seals in the valve.

You are also correct as regards relief valves. When using a tank port for power beyond you are back pressuring the relief valves which renders them inoperative.

Lastly putting the 3rd function ahead of the loader works but because it does not have a separate power beyond port it puts the third function cylinders in series with the loader cylinders. Think about how that might not be such a good idea.

You understand electrical circuits - hydraulic circuits are pretty similar. Understanding hydraulic pressure in those circuits can get a bit wonky.

Dan

 

[DustyRusty]

You don't have to make an oily mess. Get a 5-gallon container with a lid, I believe that Home Depot sells them inexpensively. Put the lid on and drill 2 holes in the top and insert the 2 hoses from the cylinder, and then move the pistons in and out. Have a helper keep the plastic pail from tipping over. If I were doing this, I would put cardboard under everything because it will soak up any spills and is easily disposed of.
You can also go to the LandPride website and should be able to find the instructions for installing the 3rd function valve. If you can't find it, give them a call, and they will help you with this. I found them to be exceedingly helpful when I ran into an issue with the 3rd function installation on my BX23S.

Land Pride

www.landpride.com

 

[Alfred_2345]

Thanks to everyone that responded. I didn't full understand Power Beyond vs Tank ports before. These posts helped and with a "little" (stayed up way too late last night) more reading now have a much better grasp. I found a couple of additional threads that filled in some holes. Here they are in case someone in the future runs across this:

Power beyond port vs tank port

Can someone please explain to me the difference between a valve with power beyond port and a valve with a tank port. I may be wrong but from my findings but power beyond ports are used when another hydraulic control valve is to be used down stream of another valve to supply hydraulic power to...

www.orangetractortalks.com

Need Education on the "Power Beyond" Port

Hello. Newbie here... I see there are "power beyond" ports available on a B2601. If I understand, this is an optional hydraulic circuit that can be utilized. My question is what is this used for? Can it be used for the front end "3rd function"? Can it be used on the 3 pt hitch as an option to...

www.orangetractortalks.com

BTW: You can use Google to search these forums to get better results. Just add "site:www.orangetractortalks.com" after your search term.

 

[TheOldHokie]

Thanks to everyone that responded. I didn't full understand Power Beyond vs Tank ports before. These posts helped and with a "little" (stayed up way too late last night) more reading now have a much better grasp. I found a couple of additional threads that filled in some holes. Here they are in case someone in the future runs across this:

Power beyond port vs tank port

Can someone please explain to me the difference between a valve with power beyond port and a valve with a tank port. I may be wrong but from my findings but power beyond ports are used when another hydraulic control valve is to be used down stream of another valve to supply hydraulic power to...

www.orangetractortalks.com

Need Education on the "Power Beyond" Port

Hello. Newbie here... I see there are "power beyond" ports available on a B2601. If I understand, this is an optional hydraulic circuit that can be utilized. My question is what is this used for? Can it be used for the front end "3rd function"? Can it be used on the 3 pt hitch as an option to...

www.orangetractortalks.com

BTW: You can use Google to search these forums to get better results. Just add "site:www.orangetractortalks.com" after your search term.

A simple picture of power beyond versus tank.

When the conversion sleeve is installed the E (center) flow is segregated from the tank flow and you have two different outlet flows

When the sleeve is remove T and E flows are combined into a single outlet flow

And next surprise is your Kubota loader valve does not route boom cylinder exhaust oil to tank. It sends it to power beyond which puts the loader and down stream cylinders in series.

And on extend the bucket spool does not route exhaust oil to tank. It directs exhaust oil to the base end port in what is called a regenerative circuit.

Dan

 

[ayak]

Apologies if you’re already aware, but be sure to keep your 3-Pt lift control lever ‘down’ when you’re running your BH77.
I zip-tie mine such that I don’t knock it or move it accidentally.

 

[dvcochran]

Hi,

New member that recently bought a used L3901 with LA575 FEL and BH77 backhoe. I don’t have any experience with tractors but I am an electronics engineer so I have some technical background.

The previous owner had installed a Land Pride 3rd Function kit. I picked up a used SGC1060 grapple that was not originally associated with the tractor. (Hoses were longer and had wrong couplings.) I replaced the grapple hoses & couplings but the grapple won’t operate. After reviewing the workshop manuals, various YouTube videos and tracing out the hose connection to the 3rd Function valve, I believe the previous owner installed the 3rd Function incorrectly. See “Existing” picture. Port names are per the Kubota manuals.
View attachment 93541
I could not find any installation instructions or videos for 3rd function valves that include a backhoe. I tried to find any relevant posts here but the search terms are too generic. I want to hook up the 3rd Function value as shown in the “Proposed” image (uses the existing hoses in place and just changes the connections at the hydraulic block).
View attachment 93542
Will this work?

From what I have learned, FEL, BH, & 3rd Func should be “in series” (i.e. one after the other in the circuit) and order shouldn’t matter. (In the future I plan on rerouting the hoses to eliminate the elbow and one hose. That routing would place the 3rd Func. in the circuit between the FEL & BH. But I first want to get things working.)

Second question: As I don’t know the history of the grapple, I don’t know what type of hydraulic fluid is in it. Is this an issue? Do I need to drain the cylinders so I don’t contaminate the tractor hydraulic fluid?

Thanks in advance,
Alfred

EE here. I would remove the connections from the end of the hoses and stroke the cylinders by hand (or some other method) to push out the oil/liquid currently in the grapple.
Hydraulics are always a compromise of the available fluid power. For example, if you want to grapple, curl, and raise at the same time, whatever is at the end of a series circuit is going to suffer from a lack of flow and (indirectly) pressure. That is why the FEL has first priority.
You could get your 3rd function form the BH and not see much drop as long as things are operated separately. There will be some drop due to port sizing and such.
Think of it this way, as long as you have a full source for flow/pressure, and an unrestricted return to tank, the operation is up to the valve and any corresponding flow control. Grabbing pressure off the tank can result in some quirky function. That said, it is done quite often.

 

[TheOldHokie]

EE here. I would remove the connections from the end of the hoses and stroke the cylinders by hand (or some other method) to push out the oil/liquid currently in the grapple.
Hydraulics are always a compromise the available fluid power. For example, if you want to grapple, curl, and raise at the same time, whatever in at the end of a series circuit is going to suffer from a lack of flow and (indirectly) pressure. That is why the FEL has first priority.
You could get your 3rd function form the BH and not see much drop as long as things are operated separately. There will be some drop due to port sizing and such.
Think of it this way, as long as you have a full source for flow/pressure, and a return to tank, the operation is up to the valve and any corresponding flow control. Grabbing pressure off the return can result in some quirky function. That said, it is done quite often.

For multi-spool directional control valves:

In a series circuit all devices get full flow and all loads move in synch. The downside is loads are additive.

In a parallel circuit flow is split across devices and loads move independently. The downside is slower actuation and lighter loads moving before heavier loads.

On a Kubota loader valve the boom spool is serial allowing the boom and bucket to move in synch. When the bucket spool is shifted out of neutral it blocks all down stream functions - e.g a third function, back hoe, or 3pt lift.

Feeding the third function or any device off the tank return of a BH77 control valve is a good recipe for valve damage.

Dan

 

[lugbolt]

there was a bulletin issued a few years back that dealt with the circuit diagram on the standard L series. It had to do with backhoe installations, 3rd functions, and loaders. Basically if you route the oil incorrectly which is often done, it'll damage the backhoe valve. But regardless, that diagram or set of diagrams, should be accessible. Any of you dealer techs have access to that? PSB-2019-104 I think???

 

[Alfred_2345]

In a series circuit all devices get full flow and all loads move in synch. The downside is loads are additive.
In a parallel circuit flow is split across devices and loads move independently. The downside is slower actuation and lighter loads moving before heavier loads.

I think I had the series/parallel circuits understood but your description crystalized it. But I still a little uncertain on open/closed circuits. Are these synonymous with series/parrallel? Or can you have a series circuit that is "closed"?

On a Kubota loader valve the boom spool is serial allowing the boom and bucket to move in synch. When the bucket spool is shifted out of neutral it blocks all down stream functions - e.g a third function, back hoe, or 3pt lift.

Thanks for the heads up. This means the 3rd function will not operate while the grapple is curling/dumping. I also took the time to look up the "regenerative" circuit you mentioned earlier. Looking at the valve diagram, I thought they had made a mistake. Now I understand what is going on. I can read valve diagrams but the more complicated ones take a little thinking to understand.

there was a bulletin issued a few years back that dealt with the circuit diagram on the standard L series. (...) Any of you dealer techs have access to that? PSB-2019-104 I think???

I tried searching for it but didn't find anything. I would be very interested in see that bulletin...

 

[TheOldHokie]

I think I had the series/parallel circuits understood but your description crystalized it. But I still a little uncertain on open/closed circuits. Are these synonymous with series/parrallel? Or can you have a series circuit that is "closed"?

In the context of a directional control valve its simply the internal routing of supply and exhaust oil between spools so open/closed center system does not matter.

In an open center system the pump is typically a fixed diaplacement pump so there must always be a route for the pump output to go to tank. Closed center systems typically utilize a variable displacement pump and output is varied to match actuator demand. When all spools are in neutral the pump output is (mostly) shut off. When a spool is shifted the pump output is increased to service the actuator. Closed center is significantly more energy efficient.

Thanks for the heads up. This means the 3rd function will not operate while the grapple is curling/dumping. I also took the time to look up the "regenerative" circuit you mentioned earlier. Looking at the valve diagram, I thought they had made a mistake. Now I understand what is going on. I can read valve diagrams but the more complicated ones take a little thinking to understand.

You got it. Plus a stalled downstream device can block the loader. That's a common problem when a coupler goes bad, the 3pt feedback linkage gets out of adjustment, or an operator fails to restore the power beyond loop after removing the backhoe.

Sadly there is no hard standard for those schematics so the same device is sometimes diagramed differently

Dan

 

[whitetiger]

PSB-2019-155-R1: L-Series; Leaking Backhoe Valves and Installing Non-Kubota 3rd Function Valves
Document ID BU2057
Status Published
Published Date 08/15/2022

Title
PSB-2019-155-R1: L-Series; Leaking Backhoe Valves and Installing Non-Kubota 3rd Function Valves
Description
This bulletin contains general information to assist you if repairs should become necessary as per the subject.
R1 Revision: Added plumbing of Remote Valves to the Standard L Hydraulic Routing Diagram on page 5 of the attached PSB.
Product Line
L-Series w/ BH-series Backhoes
Models
L2800, L3200, L3301, L3400, L3800, L3901, L4600, L4700, L4701, Grand L-40’s, Grand L-60’s - w/ BH75(A), BH76, BH77, BH90(A), BH92
Serial Numbers
No code has to be inserted here.
Issue
Backhoe valve starts leaking at O-rings on valve spools, typically seen with Standard L-series tractors equipped with Loader, Backhoe, and any non-Kubota 3rd function hydraulic valve (like WR Long or Land Pride 380-152A). If the 3rd function valve is installed in an incorrect sequence, this will create back pressure to the outlet side of the backhoe valve, causing leaks at O-rings on the valve spools.
This issue is also seen on Grand L-series tractors that have an aftermarket 3rd function or other hydraulic valve(s) installed downstream of the backhoe valve, or by operating the 3 point hitch, or rear auxiliary valves while the backhoe is attached.
Note: This same symptom of leaking backhoe O-rings can also result from a misadjusted 3pt feedback linkage or a 3pt lever that is not in the forward most position or down position of 3pt arms (also called the 3pt float position).
Solution
Correct routing is required for open-center hydraulic systems found on L-series Kubota tractors.
The correct order is - Pump> Loader Valve> 3rd function Valve> Rear Remote> Backhoe Valve> 3pt hitch> Tank.
If the loader valve or 3rd function valve is installed after the backhoe valve, normal operation of loader or 3rd function will cause high pressure to feed back through the Tank passage of the backhoe valve. The spool sealing rings are not designed to see pressure from the Tank side, and are pushed outward, resulting in external leaks on the backhoe valve. This may occur on one spool or several spools simultaneously. This is a result of the Backhoe valve design only used 2-hoses instead of a 3-hose valve with dedicated Power Beyond port, like on the loader valve.
The Kubota 3rd function valve kits on Grand-L series are typically installed using steel lines and will only fit a pre-determined location. Non-Kubota valves are typically installed with hoses and generic installation instructions to allow fit-up on various brands of OEM tractors. These generic installation instructions lead to confusion and incorrectly plumbed hydraulic systems.
Rarely is the backhoe valve damaged. Replacement of O-rings and spool cover plates is all that is needed for valve repair.
IMPORTANT
Seal damage or Valve leakage due to improper installation of hydraulic components will NOT be covered under warranty.

 

[TheOldHokie]

This issue is also seen on Grand L-series tractors that have an aftermarket 3rd function or other hydraulic valve(s) installed downstream of the backhoe valve, or by operating the 3 point hitch, or rear auxiliary valves while the backhoe is attached.
Note: This same symptom of leaking backhoe O-rings can also result from a misadjusted 3pt feedback linkage or a 3pt lever that is not in the forward most position or down position of 3pt

Did I understand that correctly - on Grand L series machines the factory remotes cannot be used when the backhoe is connected?

Dan

 

[Alfred_2345]

Quick update. Rerouted the 3rd func value in series after the loader and before the backhoe. Works great now!

Thank you to everyone that responded. I know a lot more now.