BX 23 hydraulic question

BRIGUY · Apr 20, 2004

Last weekend When I backed My BX into the garage the hydraulics sounded funny. When I went to drop the FEL it wouldn't go down unless I put the lever in the float position. I got kind of concerned (only three easy hours on her). Well I shut the BX down and checked all the controls and found the 3 point hitch lever was in the up position (the back hoe is attached) I had my wife sit on the BX hoping to get her a little more excited about my purchase, and I think she may have bumped the lever when she got off. I started the tractor and verified that moving the 3 point control had caused the problem. Looking at the connections I think I see what was going on. Could this have caused any damage??? It seemed fine but I haven't used it since.

GregW · Apr 21, 2004

Hi,
Sorry to hear of your trouble.The same thing has happend on my BX 22 a couple of times. As far as I can tell it didn't do any damage to my BX and I think you will be ok also.
I have also managed cross up the FEL hydraulic lines as well....If that hasn't happened to you your very fortunate as it is very dificult to disconnect the lines and reconnect them correctly due to the pressure trapped in the lines.

After this happened a time or so I realized the I needed to mark the lines with plastic tie wraps to help me remember where they go. The factory line markers are in a very difficult location to see and the tie wraps really make it simpler.

Good luck,
Greg

SCB · Apr 21, 2004

Briguy,
I'm confused how the 3 point lever being in the up position made your fel inoperative. What is your opinion? My backhoe has been off since 10 hours. My lever returns to center when the up cycle is complete. Does the backhoe disable the lever from returning?
Fun machines though aren't they? I've had mine for just over three weeks and have 46 hours. Gotta do my 50 hour sevice this weekend before I can play too much. Enjoy yours!
Steve

gsxr1100 · Apr 21, 2004

BRIGUY -You are ok, It will not hurt anything. The only thing it is doing is robbing PSI from your pump and mass flow.

I think SCB stated a good one. I have to agree here. How does the 3-PT lever stay up? Mine only stays down & have to move it back manually. When up it goes or returns to center….weird

I have had the lever down and it will steal power from the attachments big time.

GregW- How did you hook-up the lines incorrectly? They are color coded on the lines and the connections on the tractor rigid lines are installed so the user CANT connect them up wrong. Unless someone remove the coupling and installed new ones incorrectly.

My BX has colors on the lines and the tractor as (1) male & (1) female rigid mounted on tractor. So you can’t install them wrong.

Oh, my color codes are on each end of the hose. I guess the BX’s had some changes when building…another weird one.

rbarker · Apr 21, 2004

( Well I shut the BX down and checked all the controls and found the 3 point hitch lever was in the up position (the back hoe is attached) ... Could this have caused any damage??? )

Don't worry, it did not cause any damage. You just didn't have enough pressure. The loader, back hoe, and three point hitch all use the same pump for hydro pressure and that lever being up was robbing the pressure from the rest of the system. I'm not too sure about the wisdom of trying to get the Wife to like your tractor, though! Could seriously cut into your seat time if you are successful! /forums/images/graemlins/grin.gif

Rimmer · Apr 21, 2004

I think I can tell you exactly what was happening. The funny sound you heard was probably the hydraulic relief lifting. This was diverting hydraulic fluid flow, preventing proper operation of the FEL.

Now, why did this happen?

There is a feedback rod with a spring that is supposed to return the 3ph lever to neutral when the lift arms approach their full up position. You have one of two problems:

1. the spring tension is misadjusted. This is easily reset by moving two locknuts on the rod. You will need two 12mm wrenches. This is probably NOT the problem, however.

2. There is a feedback pin attached to the hydraulic control lever pivot. The feedback rod passes through this pin. The spring interacts with this pin to push the control lever back to neutral. It can happen that the pin twists and binds on the rod before it contacts the spring. When this happens, the rod tries to force the 3ph valve closed, but it only closes partially. This causes the lift arms to stall with the valve partially closed, resulting in a "straining" noise in the hydraulics.

There is a fix.

I have been experiencing this intermittently on my BX23 since it was new. I could never quite pinpoint the problem, and was waiting until I could be certain before talking with the dealer. I finally gave up and called him and he came out to do some troubleshooting. We were in the process of hooking up a pressure gauge to check the hydraulic relief valve setting when I started looking at the linkage more closely. We found that with the engine off, the 3ph lever in neutral, and the 3ph fully down, we could manually raise the lift arms and watch the feedback pin "grab" the feedback rod and throw the 3ph control lever to the down position.

My dealer had never seen the problem before but did some calling around and found another dealer who had seen it a couple of times. He has ordered replacement parts (a set of modified parts is available), and we are just waiting for a rainy day to do the work, since he will have to take the tractor into the shop for a day or two to do the work, and I'm using the tractor most every day right now. (Bad news is that the right fender has to come off to access the linkage.)

Hope this helps. I have never seen this problem discussed on TBN, but apparently it is not unheard of, since Kubota has modified the design slightly.

uhmgawa · Apr 21, 2004

( Last weekend When I backed My BX into the garage the hydraulics sounded funny. When I went to drop the FEL it wouldn't go down unless I put the lever in the float position. I got kind of concerned (only three easy hours on her). Well I shut the BX down and checked all the controls and found the 3 point hitch lever was in the up position (the back hoe is attached) )

Something seems to be missing here. Assuming the loader valve is
upstream of the 3PH, it is feeding the 3PH hydraulics via the power
beyond port. Even if the 3PH is deadheading the PBY port causing
the relief valve to open there is still pressure to the boom cylinder
(retract) and (extend) drain to tank. Given this the loader boom
should still have dropped.

Rimmer · Apr 21, 2004

Uhmgawa --

Looking at the hydraulic circuit in the Workshop Manual, you are exactly correct as to the layout of the curcuit.

I only have one guess, and it is only a guess. On the hydraulic schematic, the output of the relief valve, the 3ph cylinder, and the FEL cylinders are shown as being piped into a common line which then dumps into the sump. (whether it is actually this way or whether it is three separate lines I don't know.) If the relief was lifting and delivering flow to this common line, then pressure in that line might have been high enough to prevent the drain flow from the FEL cylinder, especially if the FEL was empty (and therefore light).

/forums/images/graemlins/confused.gif /forums/images/graemlins/tongue.gif

MadReferee · Apr 21, 2004

If the relief opens on a valve then its return to tank line will have pressure. Normally it has only the very low pressure from the oil being pushed out of the cylinders but in this case it would be line pressure.

However, on the B and L series, the loader's return to tank goes directly to the tank (located under the seat) with the 3pt doing it internally. There is no "common" line, so to speak, going back to the tank. Backhoes and aux hydraulics typically "T" into the loader's return to tank line right at the tank. I believe the system relief also returns directly to the tank via its own plumbing.

The BX series functions the same but I am not sure on the exact plumbing. If there is in fact a common return to tank for the backhoe, 3pt, relief and loader then that would explain your problem if the relief sticks because of the 3pt. Check to see where the loader's return to tank line goes. If it goes directly into the transmission housing with nothing T-eed into it then there could be something else.

BRIGUY · Apr 21, 2004

rbaker don't worry my wife will never cut into my butt time on the BX. I guess I should clarify this though. She woan't cut into it by playing with it herself is more accurate. I have had it almost two weeks and every time I look at the BX she finds some other non tractor related project for me to do, hence only 3.5 hours on the clock so far. I'm trying to get her to like the thing because she was so dead set against me getting it. I was laughing when I read the thread about Insuring your financed Kubota. You see my wife is the office manager for my insurance agent. I ended up having to pay off the loan on her car before she would write be a binder for the BX. I don't dare wax the BX because I know I'll have to buff her car first. Black paint stinks on daily driven vehicles (another story)

Any way my Hydraulic question.
1 I don't have a shop manual yet, will get one ASAP.
2 I do have some experience with hydraulics, not on tractors but on gas turbines, steam turbines, and control valves, ABS brake systems, snow plows etc. Same principles apply.
3 the 3 point control was about 1/2 way between the N and up positions when the problem occurred. I returned it to N problem went away. Moved the lever again and the problem returned. So it will duplicate.

Not having spent any time in the shop manual (unusual for me) and not much time on the machine i'm going to make a few assumptions please correct me it I'm wrong.

With the back hoe attached isn't it using the hydraulic feed that would power the 3 point hitch if the back hoe was removed? Again I haven't looked (working too much). So the position feedback linkage some of you are refering to is out of the picture with the BH attached?

So with out the luxury of a hydraulic schematic yet, I thought either The return line was being pressurized by too much flow going through it (not allowing the cylinders on the fel to drain back to the sump. Or that the system was dead heading lifting a PRV, again pressurizing the return. Or excessive flow robbing power from the fel.

Now this is bugging me going to get a shop manual ASAP