When you have a load on the boom and you go to lift quickly as in scooping and moving dirt. It will not shoot up quickly with full power unless the stick (left control ) is being pushed out or in (i swapped the controls to case and still same problem). If you dont touch the stick out or in ( left control ) you can only slowly lift it or else it sort of gives up like a pressure release. If you are giving slight input to the stick the boom will lift normal with full power. Is the cause for this obvious? Also one of the tracks barely works at all, but it does work somewhat. The other one works great. I took off the cover and looked at the planetaries in the final drive and changed the oil nothing looked wrong with it, no metal particles. I know I probably need to pressure test before the final drive for to rule out the final drive.
Boom: Classic symptom of a faulty load-check valve or anti-cavitation valve in the boom circuit. When you lift under load without stick input, the load-check isn't holding properly and oil bypasses, this feels like pressure dump. Adding stick movement changes the pressure dynamics enough to keep it seated. Inspect the boom lift load-check/pilot-check valve in the main control valve. It's likely stuck, worn, or contaminated. Clean or replace it, this is a common failure on Kubota excavators. Weak track: Since planetaries look good and one track works fine: Travel motor: Internal wear causing slippage—check case drain flow (high = worn) Travel valve spool: Sticking or worn, limiting flow to that motor only Brake release issue: Travel brake not fully releasing—motor fights itself Pressure test at the motor inlet under load. Good pressure but weak = motor problem; low pressure = valve or pump issue. Both symptoms point to control valve problems more than pumps,so focus there first.
Well I was limping it a long since I need to finish this job and now I lost right swing, it almost seems like it's unlocked if I'm tracking around it'll just fall towards the left and doesn't really want to swing right. It'll do it but its excruciatingly unproductive. I actually need to fix this now unfortunately.
Might be a good idea to post your machine serial number, how many hours on the unit. Any previous repairs, have all the hydraulic filters and suction screen been changed or cleaned. Simon C
Not sure where the serial number is, pretty sure it's a 90s model kx121-2. I think it has 15k hours or 5k hours. No clue about its history, I have not changed the hydraulic fluid filter or suction screen it looks reasonably clean. I am trying to put off that since it would cost 240 dollars. It was swinging perfectly fine for the last month or so maybe a little slow to the right but now it barely moves. I watched a YouTube video or 5 and was suggested to change the relief valves and then clean the spool... So I guess I will try to somehow do that without losing all the fluid on the ground.
Good luck.
If you hook up an eductor ( I own the Fox valve brand of eductor, Cat sells one also ) on the hydraulic tank, it will hold most oil and lose very little. Simon C
15K hours and 5K hours is a huge difference. I don't think 15K hours is that common for mini-ex's. 5K hours should have had the hydraulic filter changed a couple times since new.
Well it says 5k but I thought it might've rolled it's pretty hammer looks like it might've had a breaker on its whole life. It is a napa filter on it so definitely been changed I'll get a new one tomorrow. I worked on it for a few hours today, checked out the spool that controls spin motor feed. It looked fine nothing weird spring not broken clean. Cleaned it. Cracked the hoses going to feed it seemed to flow super high similar to the side that works. So I went and cracked the hose on the spin motor and it exploded like it was backed up. Fired it up and it worked perfect again. I have strong right spin again. I also attempted to look at the right track relief valve. If that is what's on the back of it's spool it looked fine no broken spring nothing weird. It really sounds like it's getting fluid and the motor for the track is messed up. The hydraulic part. I didn't mess with the boom lift but if it gets worse I will. Eventually I will fix it when I'm done with this job I need it to do I found the dipstick for that spin motor shows no oil today too.
Wondering if there was some contamination in the motor or line to it restricting flow. Maybe pieces of o-ring or something.
Started shuddering when I move boom and curl. Forgot to switch controls to check if it's always on right. Dang. Anyways I changed suction and return filters and put fresh hydraulic oil. If there seems an obvious reason for that lemme know please. im gonna check for loose fittings tomorrow other than that I'm just not sure.
Well it's gotten worse now it barely tracks and makes a hammering noise all the time. There are two houses coming from the pump and it you put your hand on the one it makes a constant hammering. Is this a bad pump?
Anyone know how to get this pump off?
Got it out with a big pry bar
I replaced only the piston that broke. It's got an hour on it it's working good. New fluid. New suction and return filters. I need some help tho. The right track and the boom lift and curl are all acting like they are pressure relieving. After losing that side of the pump I now know they are all powered by one half of the pumps pistons. I know there is good pressure it just cuts off. It's worse now after fixing it. If I run the rpm very low I can pull the stick back and lift the boom it shudders a little like it's thinking about it pressure relieving. If I rpm up and yank the stick it goes for half a second then pressure relieves. If I move the stick it sometimes works but not always. Also I think the same thing is actually happening to the track motor. I have a feel when I hit the track it just load senses then cuts my pressure. So my question is how can I figure it what the load pressure sensor or pressure relief is controlling all of those functions similarly. Curl, boom and right track. I know they are all one section of the pump becuae they didn't worse good when the piston failed. I think it's gotta be a main relief check valve I just need to find it on my tractor. I swapped the boom with another one it didn't help.
Ok well I swapped the 2 outputs at the valve body and the problem switches to the other side. So apparently my pump is bad on one output. Hope this helps anyone with these symptoms in the future. I will update when I rebuild the pump