Hydraulic Gremlins

[Furniss]

Bit of a strange problem today

I jumped back on the 8tonner after just turning it off and locking it up for the night to get a stump out I had missed (been taking a hedge out with the tree shear) and strangely it would not pick the boom up, it was working the engine but not really moving the boom, it would push the stick out and in albeit slowly - the shear would work it would crowd and not open but it would track and blade was normal - so im guessing the problem is on one circuit.
Checked oil level etc but it has just come out of workshop after a service (not had a hydraulic filter) and all o.k so got back on try it again and it was same - but then I tried making it try to track at the same time as operating boom (as it does some funny things oil sharing wise) and all of a sudden it started working normal again and seems fine.

Bit of a confusing one .... I am guessing a valve had stuck partially open/shut ? I dont suppose I have heard the last of it and wondered if anyone has any thoughts of where to look if it happens again and wont start working normally again ??

 

[V8Druid]

VDP pump on there Kev? with separate pump for tracks/blade, downstairs?
had a similar-ish issue with the 'Drema a while ago .... and sounds some thing along the same lines to a degree. .......
took some finding, but eventually nailed it down to a tiny rubber crumb in a 0.6 mm orifice in the load sensing line ....
would come and go, then stop altogether, then sort of work .... really random ...
cleaned it all out and TOUCH WOOD - A BIG PIECE not had any issues since ....
LS line is responsible for up-stroking the pump, when loaded by a motion being demanded...
if the LS line is blocked at all, the swash plate in the pump doesn't get moved to increase flow/pressure .....

that'd be my suggestion from personal experience, but I know sod all about Kubs

 

[JD450A]

What is the 8 tonner? Is it on Bowden cable controls, linkages or pilots?

 

[Furniss]

Ha

It's a kub -3a 2013

 

[V8Druid]

OK Kevin .... here's the relevant page on my LS troubles ...... http://www.ceforum.co.uk/showthread.php?t=6364&page=425 ... but it starts way back somewhere around page 410 and is well complicated

this took a bit of finding this evening