Hydraulic issues Kubota kx61-3

[Plantman01]

Anyone shed some light one this for me would be great.
I rebuilt hydraulic pump on my kx61-3, that was grand couldn’t get the system to bleed or build much pressure.. now there the only time I can get the machine to work is if I turn it off and start it up again, allowing some boom functions momentarily (very weak).
But my tracks are working spot on for around 10 seconds and then all of a sudden they start to judder then stop completely???
Turn machine off and on then it works again for another 10 seconds ?
Swapped PRV at spool valve to see would it help but it hasn’t.
Anyone any suggestions?

 

[V8Druid]

Anyone shed some light one this for me would be great.
I rebuilt hydraulic pump on my kx61-3, that was grand couldn’t get the system to bleed or build much pressure.. now there the only time I can get the machine to work is if I turn it off and start it up again, allowing some boom functions momentarily (very weak).
But my tracks are working spot on for around 10 seconds and then all of a sudden they start to judder then stop completely???
Turn machine off and on then it works again for another 10 seconds ?
Swapped PRV at spool valve to see would it help but it hasn’t.
Anyone any suggestions?

what sort of pumps are fitted to this - not familiar with the model ... have you tried reading any pressures anywhere need to determine if the pump(s) are making it and it's getting dumped or whether they're just not making pressure, first off
why did you rebuild the pump(s) ?? failure or just not making it ?? gear or VDP .. if the latter do you have any delta pressure - if not it just won't upstroke

 

[Plantman01]

what sort of pumps are fitted to this - not familiar with the model ... have you tried reading any pressures anywhere need to determine if the pump(s) are making it and it's getting dumped or whether they're just not making pressure, first off
why did you rebuild the pump(s) ?? failure or just not making it ?? gear or VDP .. if the latter do you have any delta pressure - if not it just won't upstroke

Nachi pvd28P variable piston pump.
Basically the old one wasn’t doing the business, bought a rebuild kit. I can’t even get a good pressure reading atm because it won’t give me a good enough consistency to read if you understand me. It’s very strange. At the minute I have no pilot functions unless I hold down the tracking pedals and use the joysticks then I can get some movement , put a bit more revs on it and bang no power at all.. stop and start again instantly and we have powers. I’m not sure if it is just dumping back to tank or maybe I’m getting air? Could be a round the front seal on the pump.?

 

[V8Druid]

Nachi pvd28P variable piston pump.
Basically the old one wasn’t doing the business, bought a rebuild kit. I can’t even get a good pressure reading atm because it won’t give me a good enough consistency to read if you understand me. It’s very strange. At the minute I have no pilot functions unless I hold down the tracking pedals and use the joysticks then I can get some movement , put a bit more revs on it and bang no power at all.. stop and start again instantly and we have powers. I’m not sure if it is just dumping back to tank or maybe I’m getting air? Could be a round the front seal on the pump.?

how good were the swash plates going back in ... they have to be perfect or you'll get no pressure

 

[Plantman01]

how good were the swash plates going back in ... they have to be perfect or you'll get no pressure

Well it was brand new, or are you talking about fitment wise?

 

[Mick-the-fitter]

Photo of the pump please

 

[Plantman01]

Photo of the pump please

 

[V8Druid]

is that a generic piccy?
or
you had the pump rebuilt by a third party ??
if the latter - chuck it back at them as there is obviously an issue

 

[Plantman01]

stripped pump down tonight and found out the retainer ring is cracked and bent and a few of the slippers are worn down… I see a lot of brass filings in the oil so going to have to flush that all out

What do we reckon now ? Why has this happened

 

[V8Druid]

stripped pump down tonight and found out the retainer ring is cracked and bent and a few of the slippers are worn down… I see a lot of brass filings in the oil so going to have to flush that all out

What do we reckon now ? Why has this happened

above Q.s still stand

is that a generic piccy?
or
you had the pump rebuilt by a third party ??
if the latter - chuck it back at them as there is obviously an issue

 

[Gecko]

I can’t even get a good pressure reading atm because it won’t give me a good enough consistency to read if you understand me.

Do you mean the needle is bouncing up and down so you can't take a reading?

The Hydraulic Layout Diagram shows a suction filter in the tank, have you checked for blockage?
Sounds like the pump is cavitation (or sucking air) (in addition to it's other problems).

I'd start by pulling the return filter to find out what sins are present there.

 

[Plantman01]

above Q.s still stand

Sorry this was a generic picture I had. I rebuilt myself. Need to order new parts as of now

 

[V8Druid]

Sorry this was a generic picture I had. I rebuilt myself. Need to order new parts as of now

without wishing to sound impertinent ... summat didn't go back together right to cause that level of damage in so short a time ... everything needs to be literally surgically clean before and during assembly and all components 'in tolerance' ... a grand's a lorrabucks to have to spend twice

 

[Plantman01]

without wishing to sound impertinent ... summat didn't go back together right to cause that level of damage in so short a time ... everything needs to be literally surgically clean before and during assembly and all components 'in tolerance' ... a grand's a lorrabucks to have to spend twice

I’m beginning to question the quality of the rebuild kit. It was from Chinatown direct. As I said I have rebuilt these before and had no issues with using the genuine parts.
I’m on the verge of ordering a new pump at this stage and be done with it 🥹

 

[Mick-the-fitter]

Ok is the plate holding the brass parts actually straight? End on! From the side, so if you pulled all the pistons out and laid the grey bit on a flat surface is it flat?