BT600 Backhoe Control Valve Leaking

[thatHoochguy]

Hello all, new member here after lurking and getting many questions answered that way.

I attempted to search and can't seem to find much on control valve rebuilds... hoping one of you can help me out.

I have been fighting with the control valve on my BT600 backhoe. After finding a pretty substantial leak around the top of two of the spool control rods, I took it off the tractor and replaced all O rings throughout. (Ended up finding metric O rings to fit and making two of the wipers by sanding thin a plastic washer of the same diameter, rather than pay $50 for the pack of two O rings and wipers from Kubota.) Put it all together and leak was fixed.... for a day. Four hydraulic lines later and the leaking control valve is back again...

It now seems to be leaking from the bottom of a few of the spool rods, where the caps cover the spring assembly. Haven't taken it off the machine yet to see exactly what spool but it is from the bottom this time, not the top. In your opinion should I go ahead and bite the bullet with the Kubota O rings and wipers? Could the O rings that appeared to be exact be slightly off allowing leakage? Any other things to watch out for? I am mechanically inclined but this was my first go at hydraulic valves.

I am in rural WV with nothing in the way of hydraulic shops to take this thing to for a rebuild either. One place I did find over an hour away wanted close to $1,000 to rebuild assuming it wasn't leaking between spool assembly themselves. Only 800 hours on the BX22 that its off of, way way less than that on this backhoe. Noticed control assembly is also discontinued from Kubota as far as just replacing the entire control valve, but for that price I could just buy a used BT600 from someone.....

Curious on your all's thoughts on how to proceed and if anyone else has had control valve issues.

 

[TheOldHokie]

Hello all, new member here after lurking and getting many questions answered that way.

I attempted to search and can't seem to find much on control valve rebuilds... hoping one of you can help me out.

I have been fighting with the control valve on my BT600 backhoe. After finding a pretty substantial leak around the top of two of the spool control rods, I took it off the tractor and replaced all O rings throughout. (Ended up finding metric O rings to fit and making two of the wipers by sanding thin a plastic washer of the same diameter, rather than pay $50 for the pack of two O rings and wipers from Kubota.) Put it all together and leak was fixed.... for a day. Four hydraulic lines later and the leaking control valve is back again...

It now seems to be leaking from the bottom of a few of the spool rods, where the caps cover the spring assembly. Haven't taken it off the machine yet to see exactly what spool but it is from the bottom this time, not the top. In your opinion should I go ahead and bite the bullet with the Kubota O rings and wipers? Could the O rings that appeared to be exact be slightly off allowing leakage? Any other things to watch out for? I am mechanically inclined but this was my first go at hydraulic valves.

I am in rural WV with nothing in the way of hydraulic shops to take this thing to for a rebuild either. One place I did find over an hour away wanted close to $1,000 to rebuild assuming it wasn't leaking between spool assembly themselves. Only 800 hours on the BX22 that its off of, way way less than that on this backhoe. Noticed control assembly is also discontinued from Kubota as far as just replacing the entire control valve, but for that price I could just buy a used BT600 from someone.....

Curious on your all's thoughts on how to proceed and if anyone else has had control valve issues.

Leaks from the spool seals can be caused by excessive pressure on the tank port.

Do you have any addon hydraulic valves on the tractor?

Is the 3pt control lever locked in the full down position when the backhoe is connected?

I would not guess at oring or backup washer sizes.

Dan

 

[thatHoochguy]

Thanks for the reply. Pressure is something I didn't think about, and could be possible. This started as control valve, then after new o rings I blew some old hoses, and now that they are fixed the control valve is leaking again.

I assume it was just finding next weakest link as hydraulics tend to do - change one hose may as well change them all type of stuff.

How would I go about a pressure check and what could be done if it's too high?

No aftermarket valves or third function kits installed. Just Kubota loader and backhoe using their respective connections.

As far as 3pt, I lower the small arms to their lowest setting when removing normal arms and attaching backhoe, once attached the 3pt lever remains in the neutral position unless I need to fumble with the MMM while backhoe is attached. Not sure what you mean by locked. The small 3pt arms the long arms attach to clear the backhoe, they obviously move with lever and MMM if it's manipulated.

 

[TheOldHokie]

Thanks for the reply. Pressure is something I didn't think about, and could be possible. This started as control valve, then after new o rings I blew some old hoses, and now that they are fixed the control valve is leaking again.

I assume it was just finding next weakest link as hydraulics tend to do - change one hose may as well change them all type of stuff.

How would I go about a pressure check and what could be done if it's too high?

No aftermarket valves or third function kits installed. Just Kubota loader and backhoe using their respective connections.

As far as 3pt, I lower the small arms to their lowest setting when removing normal arms and attaching backhoe, once attached the 3pt lever remains in the neutral position unless I need to fumble with the MMM while backhoe is attached. Not sure what you mean by locked. The small 3pt arms the long arms attach to clear the backhoe, they obviously move with lever and MMM if it's manipulated.

I brlieve that tractor has position control so there is no "neutral" position for the 3pt lever. The lever sets the height you want for the "small arms". There is a feedback linkage attached to the "small arms" that will automagically move the 3pt spool to raise, neutral, or lower as needed to maintain that position.

If the 3pt spool is moved to the raise position it will deadhead the pump and the tank port on your backhoe valve will see something north of 2000 PSI. The seals on those spools are only designed for about 500 PSI and they fail and leak. Putting the 3pt lever full down prevents that from happening and some models have a lock to hold it there when the hoe is installed.

To measure tank pressure put a tee with gauge on the backhoe return hose.

Dan

 

[thatHoochguy]

I brlieve that tractor has position control so there is no "neutral" position for the 3pt lever. The lever sets the height you want for the "small arms". There is a feedback linkage attached to the "small arms" that will automagically move the 3pt spool to raise, neutral, or lower as needed to maintain that position.

If the 3pt spool is moved to the raise position it will deadhead the pump and the tank port on your backhoe valve will see something north of 2000 PSI. The seals on those spools are only designed for about 500 PSI and they fail and leak. Putting the 3pt lever full down prevents that from happening and some models have a lock to hold it there when the hoe is installed.

To measure tank pressure put a tee with gauge on the backhoe return hose.

Dan

Wow. I never knew this. I will lower them all the way and see if maybe I can get lucky and the seals still be good and the leaks stop. I was under the impression center was neutral on the lever, as when I raise or lower a 3pt attachment and get it set, it doesn't move when the lever is in the center position, it must be pulled up or down to adjust then back to center to stay.

I'm curious though if that is actual position control because if that was the case it should move to wherever lever is set, and stay, correct?

 

[TheOldHokie]

Wow. I never knew this. I will lower them all the way and see if maybe I can get lucky and the seals still be good and the leaks stop. I was under the impression center was neutral on the lever, as when I raise or lower a 3pt attachment and get it set, it doesn't move when the lever is in the center position, it must be pulled up or down to adjust then back to center to stay.

I'm curious though if that is actual position control because if that was the case it should move to wherever lever is set, and stay, correct?

AFAIK your tractor has standard posotion control as I described. If the feedback linkage is misadjusted it may be giving the behavior you are desctibing. It may also be part of the over pressure issue. Get a copy of the workshop manual and read and adjust the feedback linkage.

Dan

 

[PoTreeBoy]

AFAIK your tractor has standard posotion control as I described. If the feedback linkage is misadjusted it may be giving the behavior you are desctibing. It may also be part of the over pressure issue. Get a copy of the workshop manual and read and adjust the feedback linkage.

Dan

Don't all BX's have 1/4 inching?

 

[TheOldHokie]

Don't all BX's have 1/4 inching?

Good question. The parts book shows a feedback linkage which may have led me to an erroneous conclusion

Dan

 

[TheOldHokie]

Dang - found a copy of the operators manusl and no position control. The feedback mechanism just returns lever to neutral at top and bottom position.

So much for that idea

Dan

 

[thatHoochguy]

Dang - found a copy of the operators manusl and no position control. The feedback mechanism just returns lever to neutral at top and bottom position.

So much for that idea

Dan

Lol I am actually at work and was racking my brain as how I'd have missed that all these years and how bad the adjustment must be.

I'm going to do some more investigation this week, hopefully it's just a matter of slightly miss-sized O rings in my attempt to save money. I am going to double check linkages and such however because I could see if it was loose and constantly putting pressure it could cause issues down the line.