Kubota BX25D - Backhoe return line/quick connect getting hot

[analog]

Today I needed to swap out the backhoe for a tiller and when I was done and needed to reconnect the backhoe, I noticed the quick connect that goes back to the tractor from itself was hot to the touch, so much so that I had to very quickly undo it so I could get the backhoe line back on. Once it was on, and running for a few minutes, the return line from the backhoe got hot too. I smelled it and didn't smell any burned oil smell but it's definitely hot and not something I ever remember when doing this in the past. It was not hot when I went to take the backhoe off initially (even though I had been running it for a little while). I did add some hydraulic fluid today but I'm pretty sure I didn't add too much. I know people say that 90 degree bends like at that point can be a reason for them to get hot but again I never had this problem before that I remember. What should I look at? Thanks for any suggestions!

 

[sea2summit]

It’s a hydrostatic driven tractor, every time you move it heats all the hydraulic fluid to some extent. When you do hard work and work in low range it will get hotter. I don’t think it’s anything to worry about from the sounds off it. As long as it’s not smoking or evaporating water off the hose I wouldn’t worry about it.

 

[Roadworthy]

Generally hydraulic fluid runs hot - hot enough that you don't want to handle the metal fittings with your bare hands. If you can connect and disconnect lines without acquiring first degree burns on your bare hands you're probably well within tolerances.

 

[analog]

Any particular reason why that is the only fitting that's getting hot though? All the rest of them are cool to the touch.

 

[K5lwq]

My suggestion is get a cheap infrared temp gun and take some readings and post the temps. Take several readings of other fittings and document which is at what temperature. This will help everyone give you better directions.

Do you have a hose to loop the power into the backhoe back to the return when the backhoe is disconnected?

When you say the return is the only one getting hot, which other fittings are you comparing?

 

[sea2summit]

Any particular reason why that is the only fitting that's getting hot though? All the rest of them are cool to the touch.

That is a continuous flow line so the fluid is always circulating vs say a loader hose that only gets fluid when you activate the cylinder and only hot fluid one way then likely cooler fluid on return.

 

[Leejohn]

Have you checked the couplers? If a male coupler is on the tractor side it might not getting opened with the female coupler.

 

[analog]

The return line on the tractor is a female connection. Yes, when you disconnect the backhoe, you have to hook the line that goes into the backhoe back into the return line. It's set up so that you can't mess it up. The return line was getting hot regardless if the backhoe was getting disconnected or not. I fiddled with the connector thinking maybe it was getting restricted flow somehow but I'm not sure how that would be since everything seemed to operate normally - the connectors and also the backhoe works just fine.

 

[analog]

I have a thermal camera, it's in my fire gear though so I won't be able to get it for a couple weeks, I'm on vacation. I'll post pics on this thread as soon as I can, that's a good idea!

 

[K5lwq]

If the return gets hot and the feed line doesn’t then I would say you have a restriction in that return fitting. Like what was already mentioned flow is continuous so they should both be the same temp. But they will be hotter than a fitting on the work ports of the loader or backhoe.

Look forward to seeing what the actual temps are. That will tell us a lot.

 

[sea2summit]

Have you checked the couplers? If a male coupler is on the tractor side it might not getting opened with the female coupler.

Facepalm.

If it's not open the tractor will not move, to test it just unhook the hose and try to drive. Don't try it often or for long as it is going to cause damage/prematurely wear the relief valve.

 

[ptsg]

Facepalm.

If it's not open the tractor will not move, to test it just unhook the hose and try to drive. Don't try it often or for long as it is going to cause damage/prematurely wear the relief valve.

Why wouldn't it move?

 

[sea2summit]

Why wouldn't it move?

Because when the excess flow of a priority control valve is higher than the controlled flow it shuts the valve returning all fluid to tank via the relief valve.

 

[analog]

If the return gets hot and the feed line doesn’t then I would say you have a restriction in that return fitting. Like what was already mentioned flow is continuous so they should both be the same temp. But they will be hotter than a fitting on the work ports of the loader or backhoe.

Look forward to seeing what the actual temps are. That will tell us a lot.

I would like to know what kind of restriction there would be. Would leaks cause heating up? I could see something being in the line as far as a restriction goes, but I would expect the filter to catch that before it ever circulates back to the backhoe? I suppose I could depress the balls in the line to see if they move properly.

I guess I should see if there is a hydraulic troubleshooting guide out there somewhere.

 

[DB Pilot]

Because when the excess flow of a priority control valve is higher than the controlled flow it shuts the valve returning all fluid to tank via the relief valve.

Sea2summit, I have the Kubota BH77, Last year the the dipper stick would not extend. I had that fixed at a huge cost. After the "repair" the backhoe would creep to the right when sitting still, but the BH was usable. This year, at spring startup, I find that the BH moves very slowly and weakly to the left and can be assisted by hand. It moves very quickly to the right then, I can get it to very slowly center up. I thought your continuous flow explanation would explain the creeping to the strong right side vs the weak left side movement. Everything else boom, dipper stick and bucket seem to be working quickly and strong.

Seems to me you know a little bit more about hydraulics than the mechanics here, as all I get from them is, we will look it over. Feels like I am paying them to learn the system. I did learn about spool valves on youtube, but I might be just throwing money at the BH just hoping thats the problem. Any insights would be appreciated.

 

[sea2summit]

Sea2summit, I have the Kubota BH77, Last year the the dipper stick would not extend. I had that fixed at a huge cost. After the "repair" the backhoe would creep to the right when sitting still, but the BH was usable. This year, at spring startup, I find that the BH moves very slowly and weakly to the left and can be assisted by hand. It moves very quickly to the right then, I can get it to very slowly center up. I thought your continuous flow explanation would explain the creeping to the strong right side vs the weak left side movement. Everything else boom, dipper stick and bucket seem to be working quickly and strong.

Seems to me you know a little bit more about hydraulics than the mechanics here, as all I get from them is, we will look it over. Feels like I am paying them to learn the system. I did learn about spool valves on youtube, but I might be just throwing money at the BH just hoping thats the problem. Any insights would be appreciated.

I am absolutely not a professional! Didn’t even sleep at a holiday inn.
I do enjoy figuring out how to fix things myself which often involves destructive testing

But it sounds to me like you have some bad seals in your control to me. Possibly damaged when the took it apart for the dipper? That’s pure speculation, I’d have to look at the flow chart and see how they are or aren’t related.

 

[DB Pilot]

Sea2summit, Thanks for the possible bad seal Idea. I also like to fix things myself. I must be good at it, as I always have extra parts left over after putting stuff back together.
I took the machine to an off brand dealer who was closer but I will get to the Kubota dealer this time.