Hi there, Several weeks ago I tore the center out of the swivel motor on my KX161 5-ton excavator. Upon teardown, it seems the lower bearing had failed, causing the shaft to walk sideways and tear out the middle of the piston block. I picked up a kit to overhaul it, reassembled everything and fired up the excavator, but now there's no cab movement at all. All the other hydraulics work just fine, I can track it, move the boom, bucket, dozer etc, no issues. I can push left or right on the stick and the swivel motor doesn't load up, I can see the pilot hoses twitching but there's no cab movement at all. If I loosen the hoses going to the motor, fluid comes out of them when I drop the lock lever. If I loosen the five cap screws holding the top plate on the swivel motor and lift it half an inch (thereby releasing the cab park brake) I can freely rotate the cab by pushing it, suggesting there's no issue with the reduction gearbox or anything like that. The planetary gears all look fine. My working assumption is that some garbage from the failed bearing has jammed something up down the line somewhere, and has possibly meant that the parking brake on the swing motor is engaged and won't come off. And if the brake won't release, it won't allow fluid to the motor to allow it to turn. I've checked all the filters and the bottom of the fluid tank and there's no debris, but I did remove a lot from the mesh filter on the return line attached to the swing motor, and obviously a lot of the bearing material was sitting in the bottom of the motor when I pulled it apart. Another anomaly is that if I leave the boom or dozer up in the air, it doesn't drop overnight like it used to before I blew the swing motor. I can crack the hoses on the rams and they drop at that point, but they don't settle like they used to. Does anyone know what valve controls that? Maybe it has some debris in it? Any help would be much appreciated, I'm tearing my hair out and have an expensive tech booked for Tuesday that I'd really love to cancel!
Good day My schematic is for a dash 2 but it maybe the same for later models. If you have a schematic for your machine then please post it then we will be talking about the same product. Slew which is what you refer (Cab) is driven by the same pump as blade and boom offset, the first question is if the blade & offset working as they should? In that way we can isolate the issue to the slew. I should say welcome to the forum. Kind regards Uffex
Hi, thanks for your reply. I have a KX161-3, it's from 2004. Here's a google link to the workshop manual: https://drive.google.com/file/d/1zzWrBtidOJ5SL4Yr7czNgHyMvZUHmV7C/view?usp=sharing As I stated in my post, all other hydraulics are working as they should, the problem is specifically related to the slew motor. Well that, and the weird issue with the hydraulics not unloading when the machine is off, which affects everything. Thanks for your help.
Good day This issue we have isolated to the slew as tracks are fine running from the same circuit, from this I have assumed the pump is also good. My next question is important when you use the slew is there a loading on the engine ? Kind regards Uffex
Please excuse I missed your comment regarding loading, we have a few possibilities 1/ Open check valve in the motor head 2/ No LS signal are the first we should check, I have your manual to make some information what & where so give me a spell to come back later. Kind regards Uffex
Thanks Uffex, I wasn't aware there was a check valve for the slew motor, there appears to be two relief valves physically attached to the unit, and I've removed and cleaned both. Neither had any debris in them. I'm not sure what "LS signal" is? Thanks for looking into this for me. I'm sure the issue is related to the hydraulics not unloading over time, but I don't know how to confirm that.
Good day I am less convinced this is an LS (Load Sensing) issue as you state that the hose lines twitch when you operate, providing you cannot hear or feel the motor rotating then my thoughts go to the check valves. Can you post a photo of the swing motor so I can be sure I am pointing you to the correct place. KR Uffex
Good day This may be enough however I will try to get a better illustration. KR Uffex
Improved information I believe this si what you have attched. KR Uffex
Thanks Uffex, I've attached a picture of the motor - is the green arrow the check valve(s) you were referring to? If so, I have already removed and cleaned both of them. One did have some small amount of debris in it, but it didn't make any difference. Can you confirm these are supposed to be closed when they are removed? Because I think they were both open.
Just another thought, I've noticed that one of the traction motors has started leaking a little bit. This may be due to the residual pressure in the system as the boom is still up in the air. However I have had the slew motor completely removed with all lines disconnected and it doesn't release this residual pressure. So there still must be a valve somewhere responsible for keeping the pressure in the lines and the boom in the air, but I can't locate it. I thought it might be the large check valve on the top of the valve stack but I've removed that and cleaned it, and the boom is still in the air.
Another update, I spent all morning removing the slew motor, got it on the bench and took out every bung, stopper, valve, cap on the entire thing, washed them all out and inspected them, no debris whatsoever. Everything moves freely as it should and there's no obstructions in any of the fluid galleries. Put the motor back on, filled it back up with fluid, started it up, and still no movement left or right.
Good day That is good information now we need to establish if the motor is getting the necessary pressure, remove one of the main lines, plug the motor end and the end coming from the main valve with a gauge (6000 psi. or 400 bars) operate the swing and lets measure what is arriving to the motor. Kind regards Uffex
Thanks Uffex, I don't have that kind of equipment, but I have a technician booked to do a site visit. I'll update this once I know more. Appreciate the help.
Thank you for keeping me in the loop, if you could give me a good photo of the swing motor & any label it may be good for future reference. Kind regards Uffex
Just an update - tech still hasn't made it out, probably won't be out until next week. The parking brake on the slew motor appears to be releasing now, I can turn the boom by pushing it when the motor is running and the safety lever is down. I can feel fluid passing through both input hoses to the slew motor, but there is still no left or right movement. It's as if the hydraulic fluid is passing through the motor and directly to the return. Took the relief valves off the motor again and cleaned them out (again) - still no difference. The valve springs move freely and the piston moves in and out (with difficulty) on the bench. So I'm still stumped. And the boom is still up in the air...
Good day AMay seem a strange request dead end the blade and see if the swing works. Kind regards Uffex
Latest update on this - service techs tested pressure at pump, over 3000psi left and right. Pulled motor out, took it in to get stripped and inspected. Not entirely sure what they did to fix it, but they claimed there was some kind of machining required on the top plate. They tested it on a rig and it worked in the shop, so I collected it and installed it. Now this is happening: https://youtube.com/shorts/7aydDsr28U0 So pulled it out and took it back to the shop, they have no idea but will investigate further.
Hi any update, did you solved it?