Hi Guys, Newbie here.. I have an old kubota jap spec k-045 4.5 ton excavator which is similar and shares most main parts with the kx161-2. Problem I am having is that it tracks slow or not at all up an incline or under load, but the weird thing is if I track up a hill and operate the arm cylinder it then tracks fine?! .. This tells me it's not the final drives and may be a pump, pressure related issue? Any ideas? Also I'm struggling to find an online service-parts online manual for my machine, any idea where I could find one or one for the kx161-2? Thanks!
Good day Danny My Kubota information shows that the crawler valves are mechanically operated the boom valve is directly behind that of the crawler this is hydraulically operated it would be possible if those crawler valves were not fully shifting that operating the boom would provide a pressure boost. Suggest you check out spool shifting for the crawler valves first if you have not already done so. Kind regards Uffex
Thanks for the reply Uffex, after reading it i pulled the spool out of the valve body, inspected it and found no issues in the movement with nothing restricting it. i don't have a schematic of my hydraulics to know what goes to where yet. I've noticed there are 2 pumps a large main one connected to the motor and a smaller one on the side of the engine. I notice that the hose from the smaller pump feeds the end of the valve body and when tracking straight and not operating another function it moves with a lot of pressure and I can hear a buzzing until I move another cylinder at the same time then it speeds up.
Good day Danny If I understand what you have done maybe you have missed a point - the spools are shifted by cables or rods sometimes the movement gets obstructed for example material gets lodged beneath the operating pedals please be sure the operation in the cabin results in full shifting of the spool. I do not have a schematic for your particular machine but I will look a similar model from the same stable and come back to you with some explanation, the buzzing is that a hydraulic noise or some kind of audible warning? Kind regards Uffex
Thanks mate that's very kind of you. The buzzing is a hydraulic noise and the movement in the hose is like when you operate an auxiliary valve without anything connected and see the hose tense up. I traced the spool back to the tracking levers adjusted them and made sure there was full movement and nothing was obstructing them
Danny I have taken a look at some related schematics but not the actual machine you have, from your explanation it appears that when the straight travel valve kicks in you have power to the tracks. Please try dead ending the bucket and operating the swing to see if this has a similar effect. If you can post a photo of your pump set that may also help. Kind regards Uffex
Thanks Uffex, By dead ending you mean fully closed? I did this and found that it tracked fine. So I wonder how is the straight travel valve actuated? Thanks again
I have just worked the machine for an hour so hydraulic and engine oil are hot and have found it weak/ slow to track, left/right and straight. This maybe a completely unrelated issue.. Going to install a temp gauge soon to monitor hydraulic fluid temp Thanks again for your time to help
Good day Danny According to my information you have tw hydraulic pumps one back track - when you are tracking and you operate another circuit (Boom - Bucket for example) this kicks in the straight travel valve preventing the machine veering of to the side proving the flow for the Boom Bucket, it appears to working just as it should. Can you confirm that both tracks are weak in both forward and reverse direction ? The straight line valve joins both pump flows together before they serve the spools for the crawlers, a weak pump on one side or relief valve could explain the situation. Look forward to Hera what you find. Kind regards Uffex
Thanks! It is weak tracking both backwards and forwards on an incline, on the flat it's fine. I enquired about getting the main pump pressure and flow tested but was told that it would be quite a costly process as hoses would have to be made to flow test it. I could buy some gauges and pressure test it quite cheaply if that would help The main pump is a kYB variable displacement type psvk2-25ckg-hs-6. It has 2 main outputs and also the pilot circuit. If it is most probably the pump maybe it's worth removing it and getting it stripped and diagnosed. I'm told that's a quick job for a specialist. Thanks Danny
Good day Danny Checking the pressures would give some helpful information however from your information so far I have the impression that all other functions apart from the tracks work fine (Fast as they should be and adequate power) so the issue is isolated to the tracks ? today modern hydraulic pumps are manufactured with repair in mind with most it is possible to rebuild with care and the correct information. If my interpretation of the feed back is correct we may have an issue with the central joint seals, the correct way to check this out is by pressure testing - to jump in and reseal the unit is just guess work with only a chance that we may be sucsessfull. I have attached some general information about trouble shooting crawlers it may not appear like your machine but the basics are the same and may give you a good insight as to what may be happening. Kind regards and sorry for type errors. Uffex
Thanks again Uffex, since last posting the tracking for the machine has been consistent with sufficient power. According to an earthmoving specialist he thinks it's about right for the machines age and type. However the next problem has arrived! This one is intermittent but lately the problem is there most of the time. The functions that are operated by the small pump mounted on the side of the engine are very weak. Always when cold and only ever work normally at random times when warm. The functions are, dozer blade, swing the boom and swivel. I put a pressure gauge on when weak and max pressure when dead ending is 900psi which quickly drops to around 500psi. When it's working its around 2000psi. I have checked the prv and swapped with another pumps prv with no difference. Suction filter is clean. There are no abnormal noises from the pump. I noticed that the input line to the pump is fed from the top of the main pump, so maybe there is a lack of flow? It's weird that one minute it's weak barely moving then you turn the machine off start it back up and it's normal.. Sometimes it seems to just come to life after its hot ? .. Again Like with my other issues I'm really struggling to get a specialist out to have look. Thanks Danny
Good day Danny The pump as you describe provides fluid for the functions that are intermitantt in addition to the pilot controls which appear to be working OK, if this was a internal leakage normally the pressure would drop as the fluid gains temperature so that aspect of the issue is a little strange, my interpretation of your text would lead me to check out the relief valve for that pump ( according to best practice the valve is the first the pump line meets at the valve chest ) as a first course of action if that is Ok my remaining thoughts would be remove and get the pump tested you should have 2500 p.s.i.on that circuit if my information is correct . I am not privilege to have a parts book but it is a fair bet that the relief valves for the other pumps are the same unit if that is the case you could switch over and see if the problem moves , I recently posted material regarding relief valves on this forum regarding Hitachi EX300 you can check that out it may help additional material is in the web site free to download excatech.org. Appreciate being kept in the loop Kind regards Uffex
Sorry Danny overlooked that you have switched the prv. the pump also connects to the pilot or servo system apart from the pump this is the only possible cause.If you isolate the pilot system you would be unable to test the operation I can only suggest you take it apart and give it a good check. Kind regards Uffex
Hi guys, well a few years have passed since last posting and I am back in hope of fixing this now consistent hydraulic issue. The issue is with 3 functions.. dozer, swing and swivel. They are extremely weak. These are fed by a fixed speed pump. My diagrams show this pump does not service the pilot circuit I have disassembled the pump and visually everything is tip top. It still comes back to full power from time to time which indicates that the pump is ok as far as I know. Apart from prv's are there any ideas? Thanks!
Hello DannyAussie
How did you get on with this . I have a Kubota kx161-2 that has the same issue . Weak blade ,swing,and tilt bucket function . Hopefully you were able to fix this and give some advise