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Dan
Dan, Technician
Category: Construction and Road Equipment
Satisfied Customers: 5437
Experience:  17+ yrs. shop and field experience with all major brands of heavy equipment and trucks - 1995 WyoTech graduate.
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I recently purchased a 2008 Kubota 121-3s excavator. After

Customer Question

Hi I'm Brody. I recently purchased a 2008 Kubota 121-3s excavator. After running the machine 20 min all the hydraulics immediately locked up. No boom, no blade, no tracks. I shut it off restarted it and everything ran fine for a few minutes and quit again. I've used it 2 days and it's extremely intermittent whenever the issue arises. Might take 20 min might happen instantly. There's no method behind it's completely random. Any ideas?
Submitted: 1 year ago.
Category: Construction and Road Equipment
Expert:  Dan replied 1 year ago.

Hi my name is***** will be glad to help. First lets be sure there is no major failures occuring. Check the Hydraulic filter for fine metal/debris indicating a pump or component failure.

Expert:  Dan replied 1 year ago.

If clean check the pilot safety valve to be sure it is functioning properly. Let me know the serial number of your machine

Customer: replied 1 year ago.
33872 is serial number. Filter looks good
Expert:  Dan replied 1 year ago.

Thanks for the update. I will need some time to run through the manual and gather info related to your serial number machine, Check the safety lockout on the LH console to be sure that is not causing these problems... I will check on a few things and get back to you

Customer: replied 1 year ago.
I by passed the safety switch on the lh console with a paper clip just to see if that was the problem. Not sure if that would correctly by pass it but the problem still occurred. This machine has a control lever on the right side just below the rh console that has to be engaged for the controls to work. I put a voltage meter to the solenoids that control arm engages and had power to the solenoids whenever the problem had occurred. I'm no mechanic I'm a home builder. I have a general knowledge but this has trumped me
Expert:  Dan replied 1 year ago.

Thanks for the update. Since this problem is very intermitent I would start by testing your batteries and charging system... If ok clean all your battery terminals and starter connections and grounds.... Once that is eliminated then run the machine and do a wiggle test on the harness to see if you can manipulate this problem to happen by pulling and moving the harness

Expert:  Dan replied 1 year ago.

There may be a loos connection or short in the harness or connectors

Customer: replied 1 year ago.
Whenever the problem occurs it instantly happens. There's no power loss it acts like you lift the control lever everything just instantly locks up. The boom and blade will go down but nothing will come up. The control arm runs to a manifold next to the hydraulic fill cap. There's is actually two control valve solenoids on top of this manifold. One of the solenoids is brand new and the other appears to be factory. Not sure if the other solenoid is good but if I flip positions on the 2 solenoids I have the same issue so it appears that each solenoid is functioning properly. If I remove the outside solenoid and keep it off everything acts the same. If I remove the inner solenoid I have no controls. Basically it acts like the outside solenoid is doing nothing. Although, I'm not familiar of the task each solenoid is supposed to do. One has a green with a black wire and theother is yellow with a black wire. The green wire appears to be working properly
Expert:  Dan replied 1 year ago.

also check your relays as well and your grounds.... a bad ground can cause a lot of issues

Expert:  Dan replied 1 year ago.

Thanks for the update.... Give me some time to dig into this and put my thoughts together...

Customer: replied 1 year ago.
I wiggled wires and couldn't manipulate it. I found a couple wires that was frayed and repaired them but no change. The machie has rops but no cab. There's plug ins that aren't plugged in but I can't find where they would go and a guy working for me assumed they would run a heater and wiper for a cab machine
Customer: replied 1 year ago.
I bought this machine only because I'm in a bind with getting work done before the bad weather hits in missouri. I'm building an apartment complex and no way I could beat the winter with one machine so I added another and wouldn't you know it's done me no good as of now. I really need to get it fixed and all the dealer mechanics are busy and can't get to it for a couple weeks. A couple weeks is precious to me right now so I appreciate all the help I can get
Expert:  Dan replied 1 year ago.

Use this link to help you identify your components.... It the online parts catalog.... You will need to accept the terms to view. Parts Kabota

Customer: replied 1 year ago.
Do you have any idea what the outer solenoid does?
Expert:  Dan replied 1 year ago.

are you referring to? There should be a tpss valve under the operators cab and a solenoid... I have heard that others have had trouble with this model with power loss to the solenoid under the cab floor casing these symptoms...

Expert:  Dan replied 1 year ago.

Sorry which solenoid.... Typo...

Customer: replied 1 year ago.
Maybe I'm calling them by the wrong name but the new one says solenoid with a product ID on it. They are on the hydraulic manifold just under the door that you raise to fill the hydraulics. There's a manifold that has these two (solenoids) (control valve) setting on top of it. Each (solenoid, control valve) has 2 wires coming out of them. They clip into a harness right beside the hydraulic fill cap. One harness has a green and black wire the other has a yellow and black wire. Whenever the control lever engages I can feel them click
Customer: replied 1 year ago.
Whenever the machine locks up I can move the control lever all I want and neither (solenoid, control valve) clicks. I was concerned with them because one had been replaced recently and the other was factory. There's a switch the control lever activates and gives the signal for these to operate I'm assuming. I was worried the switch was bad so again I by passed it and ran into the same issue with the machine locking up
Expert:  Dan replied 1 year ago.

What you are looking at is called the change valve. that is the block with the two solenoids at the tank. there is also an SP solenoid lower right front of the machine as well. Check for power to the solenoids when the machine is functioning and then again when it is not. This will tell you if there is a loss of power to the change valve solenoids. If the solenoids have power but are disengaging then you likely have a failed solenoid. If it is a power loss we know it is a problem before the solenoid. Let me know. Go to the parts catalog to the control valve section and click on change valve. Let me know

Customer: replied 1 year ago.
Any more thoughts?
Customer: replied 1 year ago.
I've found out that the problem occurs more whenever the machine is in a bind or struggling like trying to turn in a circle with the tracks
Expert:  Dan replied 1 year ago.

Is there power loss to those solenoids when the problem occurs or is there still power there?

Customer: replied 1 year ago.
Still power there. Now I've noticed a hissing noise inside the main hydraulic manifold that sits just inside the rh cover by the hydraulic fill. If I put any kind of pressure with a control the hissing goes away.
Expert:  Dan replied 1 year ago.

Check the change valve for debris and damaged o rings as well as proper operation of the solenoids...Also check the solenoid under the RH side of machine as well for the same(Debris, power and proper operation. Let me know

Customer: replied 1 year ago.
I checked all I could everything seems to be clean. I don't have a way to check pressures
Customer: replied 1 year ago.
I noticed this evening that whenever I hold the 2 speed button down I couldn't get the hydraulics to lock up?
Expert:  Dan replied 1 year ago.

Thanks for the update. If you have no hydraulics, all the valves and electrical test good, there's no metal in the hydraulic filter indicating a failed pump then check the pump drive coupling between the engine and pump to be sure it has not failed and is actually turning the pump. Let me know