Greetings all. Long time reader, first time poster. I have a 2010 L3700SU hydrostatic trans, with LA463 loader and BH-77 backhoe, and about 130 hours on the clock. To date, my tractor has been basically flawless, other than a few small issues that were easily repaired, most of which I attribute to my trying to do a 50 hp tractor's work with a 30 hp model. Yesterday, while lifting a load of wet mud and red clay, I heard a loud pop and saw hydraulic fluid spraying from behind the 4-tube cover on the loader front crossbar. After removing the cover, I found a substantial "blow out" in the #4 tube (top of the four, controls bucket rotation). Any of you ever had a blow out like this before? I am thankful that this occurred behind the cover as it might have been disastrous if it had happened at an exposed location. I attached an image so you can see how severe this was. I was first concerned that the rubbing between the mounting cover and the mounting plate had weakened the tube, but this was actually beside the mounting location so that probably had no impact. I am concerned that all of the other tubes are wedged between the cover and mounting location, and the vibrations might lead to similar failures of the other tubes. Again, anyone else ever have such an event occur? Prior to this event, I had never had the cover off but was surprised to see the metal to metal attachment and vibrational rubs.
Ruptured Hydraulic Line
- Thread starter hiprollc
- Start date
Looks like this message was buried behind others as it awaited moderator approvals, so it hasn't been seen by many (only 3 views, probably all mine). Anyway, replaced the #4 tube and within 6 hours of use, the new tube also ruptured. Doesn't make me feel very much love for my orange tractor right now. For the record, about two months ago, I removed the backhoe. Seemed like the backhoe never was worth the $7,000 cost, as it wouldn't dig to my expectations. Now I am wondering if there is a proportioning valve that sends pressure to the FEL and backhoe, and maybe too much fluid/pressure is available to the FEL and too little was available to the backhoe. Sent an inquiry to Kubota and they want me to carry it to my local dealer. Guess that is the next step as these steel lines are a little pricey but the time/aggravation is more of an expense. New picture attached.
Attachments
Had a local hydraulics shop build a new line with more than twice the wall thickness. Anxious to see what happens next.
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I see two possibilities:
1. The OEM tube and the replacement tube both came from a bad batch (Kubota knows, even if the consumer is never told), or
2. You have another problem related to overpressure of the system.
3. Replacing the OEM tube with a (are you certain?) thicker-wall (therefore theoretically higher pressure) tube might solve the symptom but doesn't address the problem.
Consider your system hydraulic pressure relief valve and its set-point and function.
You state your backhoe didn't perform. Did you have a / the valve(s) opened to loop hydraulic fluid through the backhoe control panel? Don't know about yours but mine is a push-pull rod under the hoe operator's left knee. If in doubt, consult the Operators Manual for both hoe and tractor.
Different tractor here, same hoe: diggin'est thing I've ever used outside the dedicated Case lineup. There are others aboard that use a -77 backhoe and don't remember any performance complaints.
I'd be talking to Kubota about warranty and making a stink if I had too. Something isn't right.
Please post back and advise your experiences so we may all learn.
1. The OEM tube and the replacement tube both came from a bad batch (Kubota knows, even if the consumer is never told), or
2. You have another problem related to overpressure of the system.
3. Replacing the OEM tube with a (are you certain?) thicker-wall (therefore theoretically higher pressure) tube might solve the symptom but doesn't address the problem.
Consider your system hydraulic pressure relief valve and its set-point and function.
You state your backhoe didn't perform. Did you have a / the valve(s) opened to loop hydraulic fluid through the backhoe control panel? Don't know about yours but mine is a push-pull rod under the hoe operator's left knee. If in doubt, consult the Operators Manual for both hoe and tractor.
Different tractor here, same hoe: diggin'est thing I've ever used outside the dedicated Case lineup. There are others aboard that use a -77 backhoe and don't remember any performance complaints.
I'd be talking to Kubota about warranty and making a stink if I had too. Something isn't right.
Please post back and advise your experiences so we may all learn.
Thanks, Stubbyie, for the thoughts and suggestions.
For #1, Kubota offered no solution and hasn't returned my calls. Said they would provide info to the selling dealership but they have not communicated any info. The factory warranty ended less than 2 months ago... perfect timing for Kubota.
For #2, area rep said there were no proportioning valves or control adjustments. I have read through the manuals and no mention of adjustments either.
For #3, I replaced the 1 mm (.040" or forty thousandths) thick steel line with an .083" (83 thousandths) thick JIC seamless line. Hydraulic engineering design tables state that the .040 is good for approximately 1800 to 2200 psi max working pressure (with a 4 to 1 safety factor), with a theoretical burst pressure of around 6000 psi. The same tables state that the replacement tube is good for approximately 5000 psi max working pressure and a theoretical burst pressure of around 16,500 psi. My replacement line now has threaded connections so I am looking for a pressure gauge that has a "telltale" needle to let me see what maximum pressures are being developed.
Lastly, the BH77 hydraulics all work fine, as far as motion and control, but there just isn't much power. This past year I built a 30 x 40 steel building but could not even use the backhoe to dig the footing for my 6" slab. To say I am disappointed in the backhoe is an understatement. I, like you, had previously operated a Case Construction King series hoe, so maybe I am expecting too much. Then again, maybe the 30 hp pto rating just isn't enough power for the backhoe.
I will update if anything changes and share here.
For #1, Kubota offered no solution and hasn't returned my calls. Said they would provide info to the selling dealership but they have not communicated any info. The factory warranty ended less than 2 months ago... perfect timing for Kubota.
For #2, area rep said there were no proportioning valves or control adjustments. I have read through the manuals and no mention of adjustments either.
For #3, I replaced the 1 mm (.040" or forty thousandths) thick steel line with an .083" (83 thousandths) thick JIC seamless line. Hydraulic engineering design tables state that the .040 is good for approximately 1800 to 2200 psi max working pressure (with a 4 to 1 safety factor), with a theoretical burst pressure of around 6000 psi. The same tables state that the replacement tube is good for approximately 5000 psi max working pressure and a theoretical burst pressure of around 16,500 psi. My replacement line now has threaded connections so I am looking for a pressure gauge that has a "telltale" needle to let me see what maximum pressures are being developed.
Lastly, the BH77 hydraulics all work fine, as far as motion and control, but there just isn't much power. This past year I built a 30 x 40 steel building but could not even use the backhoe to dig the footing for my 6" slab. To say I am disappointed in the backhoe is an understatement. I, like you, had previously operated a Case Construction King series hoe, so maybe I am expecting too much. Then again, maybe the 30 hp pto rating just isn't enough power for the backhoe.
I will update if anything changes and share here.
gpreuss
New member
Lifetime Member
Equipment
L3200DT w/FEL, K650 Backhoe, 5' Rotary, 40" Howard Rotavator, 6' Rhino blade
I started out with Kubota 35 years ago with an L185DT with FEL and a K650 backhoe (whichever model had a PTO hydraulic pump - K650 or L650). Both the FEL and backhoe had independent hydraulic systems.
In its first 6 months, EVERY one of the backhoe hydraulic hoses burst, usually covering me in hot oil. I never had one of the replacement hoses fail. The backhoe boom had a bunch of power, the dipperstick seemed weak as hell, but the bucket wrist action was where all of the power was.
I had a pressure gauge on the loader and one on the backhoe. I adjusted the pressure relief on each implement so a single function gave me about 2200 PSI. I'm not sure how it worked out, but I could get readings of over 3000 psi by using two functions at once, i.e. FEL lift + curl.
I would invest in a gauge or two and a couple of "T" fittings. Find out what the pressures really are! Wet mud and clay are about as heavy a load as the FEL can lift. If the relief valves are mis-adjusted you may well be going over the rating on the front, and never seeing the rating on the rear.
In its first 6 months, EVERY one of the backhoe hydraulic hoses burst, usually covering me in hot oil. I never had one of the replacement hoses fail. The backhoe boom had a bunch of power, the dipperstick seemed weak as hell, but the bucket wrist action was where all of the power was.
I had a pressure gauge on the loader and one on the backhoe. I adjusted the pressure relief on each implement so a single function gave me about 2200 PSI. I'm not sure how it worked out, but I could get readings of over 3000 psi by using two functions at once, i.e. FEL lift + curl.
I would invest in a gauge or two and a couple of "T" fittings. Find out what the pressures really are! Wet mud and clay are about as heavy a load as the FEL can lift. If the relief valves are mis-adjusted you may well be going over the rating on the front, and never seeing the rating on the rear.
Burt
New member
Equipment
L3700SU, box blade, 6 foot rhino blade, 1 bottom plow, 3 point receiver hitch.
hipprollc,
I too have an L3700SU but no backhoe...didn't want one and for that, I hired out what I needed.
However, I do recommend taking your rig to a dealer and ask them to check/verify all pressures in your unit. Please read on down further.
As far as putting in a "stronger" unit, by doing that, you will both void any warranty and perhaps create a new problem and then you're really out of luck or warranty.
Another tip: These came with faulty valves to begin with (the one that controls the 3 point). Mine was replaced under warranty and it works smoothly now vs. jumpy. If you can search OTT for my old post, you will perhaps read my saga. I did this all through the factory rep, insisting on dealing with him first and only, then the dealer. The dealer was back stepping all the way until I got to the factory rep.
So, I suggest the following: Contact your dealer via phone first. Write down the name of who you talked to and record it. Keep a record of all contacts, including date and time. Ask about the valve replacement for the L3700SSU (jumpy 3 point). If no answer or backpeddling, ask the phone number or e-mail for the factory rep. If no, then ask for the Kubota number. If no, then send a certified letter to the dealer's receiving agent. Put in the letter your requests to discuss this with a factory rep and send a copy to your state's consumer affairs or business practices office...usually associated with your attorney general. In your letter refer to "latent defect," or "fitness for purpose" purposefully. Don't over-blow the language or make any threats, just ask for information and communication. Suggest that you can bring the unit in for inspection and observation. Put your serial number(s) in your letter also. Kubota records their warranty by the unit's serial numbers. Be prepared for a delay or a miracle. I got the miracle. Go up the chain for results. The answers at the bottom are not usually the ones that can make decisions.
Burt
Dear HiProLLC:
I like the idea of using a tattle-tale gauge to determine high and low pressures (for those unfamiliar, similar to a thermometer that has internal needles or magnetic particles that are moved by the primary indicator).
Yeah, you can find them, but the good ones aren't cheap.
You may find a better deal by investigating pressure logging devices that connect to your hydraulic system and then can download to your computer. Or perhaps a pressure transducer (you'd have to have a laptop aboard).
Over time I've seen a few 'surplus' or 'take-offs' data logging models at offbeat websites along with new at good prices if you look around. I don't have named 'sites at hand because I was just trolling the 'Net for interesting stuff, not searching for particular devices: just one of those things I mentally file away for future use.
Some of the later models upscale digital multimeters have the capability to download from a logger and display the results.
If you went with a logger you'd have a record of possible pressure spikes you could show Kubota. If using a gauge, try photos or even movies using a digicam.
You mention the warranty is gone by two months. Follow the advice of another poster about his experiences and keep making noise until you get attention.
By the way, you get extra credit for knowing and/or researched characteristics of the particular hydraulic tube you used as replacement. Keep in mind that the theoretical burst pressure is a static condition while in fluid hydraulics the momentum of the fluid (think water hammer in home plumbing) and impulse loading can and does play a significant role in system failures--you may not have as much safety margin (slop, tolerance, overdesign) as you think. Which leads me back to the observation that something isn't right.
A different poster in this chain commented that every one of his hoses burst within six months of new. I think he did mean hoses, not tubes. I just got through changing all the hoses on my BH-77 backhoe: the OEMs lasted 15-years. And on the replacements I've formed the habit of shutting down by grounding both ends (TLB) and relieving all hydraulic system pressure--removing all (~2,000+ psig) pressure on every hose.
Please continue to post back with your experiences that we may all learn.
I like the idea of using a tattle-tale gauge to determine high and low pressures (for those unfamiliar, similar to a thermometer that has internal needles or magnetic particles that are moved by the primary indicator).
Yeah, you can find them, but the good ones aren't cheap.
You may find a better deal by investigating pressure logging devices that connect to your hydraulic system and then can download to your computer. Or perhaps a pressure transducer (you'd have to have a laptop aboard).
Over time I've seen a few 'surplus' or 'take-offs' data logging models at offbeat websites along with new at good prices if you look around. I don't have named 'sites at hand because I was just trolling the 'Net for interesting stuff, not searching for particular devices: just one of those things I mentally file away for future use.
Some of the later models upscale digital multimeters have the capability to download from a logger and display the results.
If you went with a logger you'd have a record of possible pressure spikes you could show Kubota. If using a gauge, try photos or even movies using a digicam.
You mention the warranty is gone by two months. Follow the advice of another poster about his experiences and keep making noise until you get attention.
By the way, you get extra credit for knowing and/or researched characteristics of the particular hydraulic tube you used as replacement. Keep in mind that the theoretical burst pressure is a static condition while in fluid hydraulics the momentum of the fluid (think water hammer in home plumbing) and impulse loading can and does play a significant role in system failures--you may not have as much safety margin (slop, tolerance, overdesign) as you think. Which leads me back to the observation that something isn't right.
A different poster in this chain commented that every one of his hoses burst within six months of new. I think he did mean hoses, not tubes. I just got through changing all the hoses on my BH-77 backhoe: the OEMs lasted 15-years. And on the replacements I've formed the habit of shutting down by grounding both ends (TLB) and relieving all hydraulic system pressure--removing all (~2,000+ psig) pressure on every hose.
Please continue to post back with your experiences that we may all learn.
As an update, I replaced the original factory line with a custom built, locally sourced hydraulic line, with all new fittings and a pressure gauge. My pressure gauge was a 0 to 5000 psi, liquid filled style, with a Maximum Pressure Indicator. On the first day of use with the new gauge, I wanted to determine how high the hydraulic pressure could be expected to rise under, what I consider, reasonable duty. While back dragging, with the bottom front lip of the bucket down and slowly pulling backwards, I know you are supposed to operate in a float mode to allow the relief valve to work. However, sometimes, stuff happens, and you mistakenly are not actually in float. While experimenting with this back dragging condition, I easily pegged the gauge. That means that the line in question exceeded 5,000 psi very easily. The good news is that the new line held up fine. The bad news is that I will not be back dragging like this again, although it is something that I have done with other FEL's through the years with no issues. Guess it is time to ditch the Kubota for something designed to actually do that kind of work. It does make me wonder why Kubota would use tubing not designed for such an easily attainable pressure.