Slew problem, kobelco sk75ur

[Thebrumby]

Hey guys! first time poster, Long time reader.

I have kobelco 75ur and it has a weak slew in both directions. Weak as in it struggles to swing in the air with no load on flat ground (only slightly better at full rev compared to idle) When i press a travel lever slightly (not enough to make the machine drive) the slew works fine again.

Everything else seems ok, tracks drive with heaps of power. Boom and stick maybe slightly slower compared to other excavators of similar size, dunno if normal or not but can easily dig and pick itself up.

This machine was parked up for 2 or more years before i got it last week. and this problem may have been pre existing. I have no history on it. I had to add 60l of hydraulic oil to get the tank level correct

 

[John C.]

Not a lot of those machine in this country. Do you have a hydraulic schematic?

 

[uffex]

Good day
See attached may help.
Kind regards
Uffex

 

[John C.]

That is helpful but I think the problem is a system issue. He mentions that it works properly when a travel function is slightly actuated at the same time.

 

[uffex]

Good day
A load sensing system can suffer from this issue when the drain orfice has blocked without a hydraulic schematic as JC suggests it is difficult to help more.
KR
Uffex

 

[Thebrumby]

Not a lot of those machine in this country. Do you have a hydraulic schematic

hey john , thanks for the reply. i have the rest of the manual too if need

 

[Thebrumby]

yea so the machine won't swing on idle, but at full rev its able to swing but in a slow and gutless fashion. As soon and you push or pull the left travel lever,even just slightly , the swing goes back to normal.

 

[Tones]

yea so the machine won't swing on idle, but at full rev its able to swing but in a slow and gutless fashion. As soon and you push or pull the left travel lever,even just slightly , the swing goes back to normal.

I'm on a new one (600 hrs) and its the same. The service bloke says "it's the way they are". It may get fixed after the warranty runs out.

 

[John C.]

That is a strange looking way to run the swing. The top spool on the second valve shows travel priority and it is the normal parallel passage that supplies oil to the swing control spool. The valve is also open center and the swing spool when shifted still has the center passage with a restrictor that allows P2 oil through the spool instead of stopping flow so it would all be available for the swing through the parallel passage. Basically oil can flow down the parallel passage to the swing function and down the center passage at the same time. When you shift the travel priority valve by moving the left side travel lever you now have P1 and P2 supplying oil to the swing at the same time which is more than enough oil to make the swing work fine.

You have a stack of solenoid valves labeled 15 on the schematic. Does your book explain the purpose of the neutral cut solenoid, neutral cut spool and what it affects? It looks to me like you have to shift the neutral cut spool in order to stop flow through the center of the valve in order to force flow down the parallel passage to supply the swing. The only other thing I can think of is the restrictors in the swing spool are worn over size or gone. That doesn't make much sense.

 

[Thebrumby]

Just a guess...These machines have cab interference system, where the closer the backet is to the cab the slower the hydraulics functions get and if you get into the exclusion zone it shut the hydraulics off untill you press a button on the joystick. But its not supposed to shut off travel, slew and blade. Just the boom/stick functions

 

[Thebrumby]

Heres the manual i have, it explains it better

https://www.pdfhost.net/index.php?Action=Download&File=21ab4e5ac6b8b14840279c8d2efbf494

 

[Thebrumby]

I was told today that it maybe a stuck valve of the independent travel solenoid, not necessary a failed solenoid but the valve block itself may have some contaminates. But his experience was on an early 90’s kobelcos

 

[Thebrumby]

I'm on a new one (600 hrs) and its the same. The service bloke says "it's the way they are". It may get fixed after the warranty runs out.

Ask the service guy if its made for people with three arms, or what happened to the passenger. Gotta be a special operator to run this machine efficiently aye.
Wow at 600hours! I bet this is a really common issue. Mines close to 10k hours and i have a second one at 5k without this issue

 

[uffex]

Good day
Had a brief look at the circuit it appears that the connecting element to crawlers and swing is that of the "Travel Priority" suggest the connection "PO" is plugged and see what reaction the machine makes.
Kind regards
Uffex

 

[John C.]

I believe the travel priority valve is working correctly as the swing works normally when left travel is actuated.

I caught the other thread on this topic and see that the system has a micro processor that inhibits functions under certain conditions. I suggest there is a proximity sensor or encoder not working correctly and the electronics are affecting the operation of the swing. Problem seems to me to be the neutral cut valve is staying in the open position allowing flow to return to tank and not build pressure to operate the swing through the parallel passage.

 

[Thebrumby]

I believe the travel priority valve is working correctly as the swing works normally when left travel is actuated.

I caught the other thread on this topic and see that the system has a micro processor that inhibits functions under certain conditions. I suggest there is a proximity sensor or encoder not working correctly and the electronics are affecting the operation of the swing. Problem seems to me to be the neutral cut valve is staying in the open position allowing flow to return to tank and not build pressure to operate the swing through the parallel passage.

Maybe i’ll disconnect its power supply to see if any changes happen, if i can find it. Only sensors i know off are the boom and stick positioning sensors (just simple potentiometers), and those were bypassed years ago with the switch under the seat. Maybe some pressure sensors

 

[Thebrumby]

Just found this, explains about the cut valve

 

[Thebrumby]

Again

 

[John C.]

It doesn't explain how the system is supposed to work. It only shows the components in the system.

 

[Kobelco ireland]

Please post a picture of the machine and its instrument panel so I can know which model it is