Swing motor slow intermittent ex120-2

[northmanlogging]

Slow swing and the swing brake is goofy, but has always been goofy

the slow swing thing started recently, but if you slam the bucket down or shut machine off and on it will usually clear up, Its got decent power (well not really but yeah) for an old machine, but when it gets slow its almost like its bye passing the motor completely the pump doesn't even try.

The brake issue has been ongoing since I bought it 4 years ago, in that it slows down ok, but then relaxes once it gets to a certain point and then does nothing, so if your working on a slope, it never really gets out of control, but can be irritating.

but if the machine is off, brake holds good for awhile at least, eventually bleeds off and you can push it around a little

(note, this is why you should always chain down the bucket when trailering excavators...)

Generally speaking the machine has plenty of power, though it seems lately when the swing goes wonky everything else gets slow too, I regularly stump with it, and load logs...

I've heard cushion valves, and I've heard wiring gremlins, Hoping to narrow it down some (as in not the swing motor cause... ya we broke yo)

Thanks for any help

 

[Ronsii]

Bad ground to the computers....

 

[TVA]

Bad ground to the computers....

I will second that! That’s where I would start! Check all the powers and grounds under load for voltage drop! I am pretty sure that pump completely controlled by computer ( TVC ) by two solenoids! There’s no mechanical/hydraulic regulators!

 

[Ronsii]

I think I'd also install a voltage monitor in the cab so you can keep an eye on the feed to the electronics as it could also be the charging system giving you an over/under voltage situation and messing with the controls.

 

[John C.]

The brake is spring applied and hydraulic released. Unless it's completely broken, it can't release without the engine running.

All the symptoms sound like an old machine with dirty hydraulic oil.

 

[northmanlogging]

The brake is spring applied and hydraulic released. Unless it's completely broken, it can't release without the engine running.

All the symptoms sound like an old machine with dirty hydraulic oil.

nah leaks to much to have any dirty oil left in it... I change filters regularly though.

 

[northmanlogging]

Bad ground to the computers....

Any hints on where to look for these grounds? I'm not even real clear on where the computer is, I know it has one, and its likely in the cab somewhere... but me and wiring don't get along, as I'm a little bit color blind... and like to let the smoke out of things.

 

[uffex]

Good day
Please see attached may help you resolve the problem.
Kind regards
Uffex

 

[uffex]

Good day
My policy is not everybody's experience but if you begin at the source of the problem as a starting point it avoids much of the guess work.
Kind regards
Uffex

 

[PapaK]

Did you ever clear this up? IT sounds similar to my 1995 kobelco SK120LC.

It will work fine and then after a heavy swing as it slows down it starts to chatter. Not clunking or grinding but a bmp-bmp-bmp sound.

After it does this once, the machine starts to lose all swing function. A few minutes later it won't swing at all and doesn't sound like the machine is really trying to swing.

I just resealed all the cylinders. I changed out all the hydraulic fluid at the same time and the new fluid appears milky already. I can't see how water is getting in anywhere to make it that silky especially when the fluid was all changed while the cylinders were off.

Could the fluid appear milky from air? I'll start checking grounds like this group said. I bought the machine off an old farmer and there was a processing head on it so the wiring is a mess because they added that.