Kubota KX41-3v. Hydraulic Issues

[JCS]

Hi All,

Can someone please help..!!!

I have owned a Kubota KX41-3v excavator for over two years and it has been a true workhorse, regularly maintained and greased daily until..?

One day whilst using it I noticed that right hand track begun to slow down. At first I thought it was my imagination but then it got worse. At the same time the main boom hydraulic began to slow. I continued to use it until the track actually stopped and so did the main boom (up & down). I then turned everything off and left it overnight. The following morning I started her up and everything burst back into life and worked fine. Until around ten minutes later when exactly the same happened again. Ever since it has remained the same. When the unit is left overnight it will work fine the next day for around ten minutes, then the main boom slow and stops as does the right track.

I have changed all of the hydraulic filters and oil and have has two independant engineers come out to try to work out what was wrong and both have drawn a blank..? They have tested the hydraulic pumps at all their stages and all register correctly.

This is now so frustrating..... has anyone out there ever come across this or had any similar problems..?

Any help greatly appreciated

[ianoz]

I would imagine it has 2 pumps , and one needs a rebuild . Had the same thing happen on an IHI excavator . Check to see if it has two pumps .

[Muz]

Sounds like a main relief spool sticking as the block warms up. The valve block is usually split into certain grouped functions, and a relief valve governs the pressures in each section. Have you asked a kubota dealer about it? ..it isnt a common problem for Kubota .. do you mean a KX41 dash 3 with variable track ?.. I meant to ask ? .... oh and welcome to the forum BTW

[JCS]

Thanks..!

I would imagine it has 2 pumps , and one needs a rebuild . Had the same thing happen on an IHI excavator . Check to see if it has two pumps .

I believe that it has three pumps from memory and that the last engineer took pressure readings from each when the unit was hot and everything checked out.

But thank you for the information, this is another lead for me to follow up.

[JCS]

Thank you for the help..!

Sounds like a main relief spool sticking as the block warms up. The valve block is usually split into certain grouped functions, and a relief valve governs the pressures in each section. Have you asked a kubota dealer about it? ..it isnt a common problem for Kubota .. do you mean a KX41 dash 3 with variable track ?.. I meant to ask ? .... oh and welcome to the forum BTW

Thanks for the info and the welcome..!

Great to finally have people I can discuss these issues with..!

I think I know what you mean, I have had an engineer go through each of the small pressure relief valves one at a time on the block which feeds these two hydraulic circuits and tested and cleaned each one. This unfortunately made no difference.

Speaking with Kubota direct. I haven't tried this I've always spoken to their agent who haven't offered much help.

My excavator is the Kubota KX41-3v with twin speed and varying width tracks, 2004.

[Muz]

Thanks for the info and the welcome..!

Great to finally have people I can discuss these issues with..!

I think I know what you mean, I have had an engineer go through each of the small pressure relief valves one at a time on the block which feeds these two hydraulic circuits and tested and cleaned each one. This unfortunately made no difference.

Speaking with Kubota direct. I haven't tried this I've always spoken to their agent who haven't offered much help.

My excavator is the Kubota KX41-3v with twin speed and varying width tracks, 2004.

Well if the pump pressures are ok, something isnt letting that pressure through to the service, which is why I suggested a relief fault. Its unlikely to be a servo issue because one of your services at fault is a track motor, which uses a direct conection to the block, and isnt servo operated.

I might have a schematic for a dash 2 that might be similar .. I'll have a look for you

[ianoz]

Well, This was my experience . The machine got slow with one track and some of the hydraulic functions .Fitter rebuilt one of the pumps,and all returned to normal .
Many years later , Machine started doing the same thing .Fitter that had done it the first time had retired ,got another mob to do it .Told them One pump had been rebuilt ,so it would be the other pump .
They pressure and flow tested it and said it was good . So refaced the main relief valve ,This did not fix it .
Used a thermal heat sensing gun thing and decided the control valve was bypassing ,so rebuilt it .
Took it and used it ,Had a slight improvement ,but within 2 weeks was back to shit again .
Took it back and told them to try again .
Went back a couple of days later .
They had one of the pumps stripped down .,and said it was stuffed .
I said ,But you flow and pressure tested it ,and you said it was good .
Moral is apparently , experts and their tests do get it wrong ..

[Muz]

Moral is apparently , experts and their tests do get it wrong ..

Aye thats for sure And I once had a good guy tell me, that sometimes you can get flow but without pressure, and vice versa, which also can give misleading results. A hydraulic fitter usually carries a test meter which measures both simultaneously , and is a different kettle of fish to the usual pressure guages most of us work with

[JCS]

Good Advice...!

Great, thanks for the info. It looks like I have some options to look at. I think you are dead right about the engineers. No one has been able to diagnose the fault, they just wanted to change lots of parts, "Caching ££" on his part but no guarantee of a fix. All the engineers who have looked at it so far just seem to be "fitters" and not "Engineers" in the true sense of the word..!

[JCS]

Good Advice..!

Well, This was my experience . The machine got slow with one track and some of the hydraulic functions .Fitter rebuilt one of the pumps,and all returned to normal .
Many years later , Machine started doing the same thing .Fitter that had done it the first time had retired ,got another mob to do it .Told them One pump had been rebuilt ,so it would be the other pump .
They pressure and flow tested it and said it was good . So refaced the main relief valve ,This did not fix it .
Used a thermal heat sensing gun thing and decided the control valve was bypassing ,so rebuilt it .
Took it and used it ,Had a slight improvement ,but within 2 weeks was back to shit again .
Took it back and told them to try again .
Went back a couple of days later .
They had one of the pumps stripped down .,and said it was stuffed .
I said ,But you flow and pressure tested it ,and you said it was good .
Moral is apparently , experts and their tests do get it wrong ..

Great, thanks for the info. It looks like I have some options to look at. I think you are dead right about the engineers. No one has been able to diagnose the fault, they just wanted to change lots of parts, "Caching ££" on his part but no guarantee of a fix. All the engineers who have looked at it so far just seem to be "fitters" and not "Engineers" in the true sense of the word..!

[JCS]

Thank you for the help..!

Well if the pump pressures are ok, something isnt letting that pressure through to the service, which is why I suggested a relief fault. Its unlikely to be a servo issue because one of your services at fault is a track motor, which uses a direct conection to the block, and isnt servo operated.

I might have a schematic for a dash 2 that might be similar .. I'll have a look for you

Thank you so much for your help, I look forward to an update if you can find any further info..!

[Muz]

Thank you so much for your help, I look forward to an update if you can find any further info..!

Theres no schematics in the parts books after I checked, but what they do is show the lines and position of each spool in the block with its service name, so you can see what goes where

[JCS]

Thanks...

Theres no schematics in the parts books after I checked, but what they do is show the lines and position of each spool in the block with its service name, so you can see what goes where

Thanks for the info...

[Lc140-7]

Help

Did you ever find out what the problem was? I have a kx36-3 2010 doing exactly the same, fine until warm then track and dipper slow down/stop. Tested pumps all good

[v8druid]

Great, thanks for the info. It looks like I have some options to look at. I think you are dead right about the engineers. No one has been able to diagnose the fault, they just wanted to change lots of parts, "Caching ££" on his part but no guarantee of a fix. All the engineers who have looked at it so far just seem to be "fitters" and not "Engineers" in the true sense of the word..!

I call them 'box fitters' these days ..... take a new one out the box and fit it .... if that don't cure it try another box .... diagnostic fitters are very rare these days .... if they can't plug it in and have it tell them what's wrong, 95% of 'em are f**ked ... sad state of affairs really