Bobcat 325 Mini-ex hydraulic problem

[shantie]

My Bobcat 325 Mini excavator has lost all function on the right-hand side, I have tested the relief valves, and the hydraulic pump, everything seems fine. looking for ideas to check next

 

[oldnslo]

Is the joystick hydraulic pilot or electric on that model? Either way I would check to see if getting a pilot signal or command from joystick to valves.

 

[shantie]

joystick hydraulic pilot

 

[shantie]

All left side controls are functional, and all auxiliary (blade and boom swing) controls work

 

[oldnslo]

I would double check to confirm that you are getting pilot pressure to the right joystick. Some of those systems had “pilot supply” valves for each joystick vs one common supply valve that you could have is controlled by the safety circuit.

 

[shantie]

I forgot to add that I do not have any right-hand drive as well, there doesn't seem to be any hydraulic pressure on the right-hand valve bank, I have tested the pump 1 which is producing the appropriate pressure.

 

[oldnslo]

Do you have a hydraulic schematic? Your system could have unloading valve for each pump vs a common unloading valve. I believe some excavators where built this way.

 

[shantie]

Do you have a hydraulic schematic? Your system could have unloading valve for each pump vs a common unloading valve. I believe some excavators where built this way.

Yes I have the service manual and the hydraulic schematic the unit is set up as ISO controls so on the right joy stick is the boom controls and bucket control, the right travel is a foot/rod control. Could a failed valve be letting oil dump bank to tank?

 

[oldnslo]

Yes I have the service manual and the hydraulic schematic the unit is set up as ISO controls so on the right joy stick is the boom controls and bucket control, the right travel is a foot/rod control. Could a failed valve be letting oil dump bank to tank?

Depending on how the circuit is setup it may have a valve or valves to unload the pump or pumps. Can you attach a picture or pdf of the hydraulic schematic showing the pumps, control valves, joysticks, etc. That could help us identify potential valve or valves that could cause the problem you are experiencing.

 

[shantie]

Attached files from service manual

 

[oldnslo]

Looking at the schematic the pilot signal line is common for both joysticks. It also does not show any unloading valves for any of the three pumps.

Was this a sudden failure of all right hand functions or something that was intermittent and now is completely not working?

I would first start by confirming you have pilot pressure to the joystick then would check to see if getting pilot pressure to the valves. I am not sure if lock out safety valve has two separate supply ports one for each joystick of if there is a tee after the lockout. I believe pilot supply is approximately 360 PSI.

 

[shantie]

The right side was an instant complete failure I had to tow it out of the wood with my skidder, I understand the pilot valve issue controlling the joystick functions but how would it effect the right-hand travel function?

Thank you for helping me troubleshoot, I will check pilot valve first thing in the morning.

 

[oldnslo]

Sorry, I missed the right hand drive not working in your post. Does either boom or bucket functions work? Reason for asking these functions are also supplied by pump 1.

How did you test pump 1 for pressure? I see test ports shown at pump outlet but curious what valve you shifted to build pressure.

Is it possible to install a gauge on the test port of pump 1 and monitor that gauge while operating the functions pump 1 feeds? Curious to see if pressure changes at all.

Possible relief failed open but then you shouldn’t have seen any pressure which contradicts what you have stated. This would affect all of the functions and depending on relief valve design it could be a sudden failure. That is the only valve the only valve shown in the schematic that would affect all those functions.

 

[shantie]

we unhooked the pump 1 pressure line installed a line with a pressure gauge and a ball valve beyond the pressure gage from the valve connected this into the supply line, this way we could slowly close the valve and wat the pressure rise.

 

[oldnslo]

we unhooked the pump 1 pressure line installed a line with a pressure gauge and a ball valve beyond the pressure gage from the valve connected this into the supply line, this way we could slowly close the valve and wat the pressure rise.

By doing that you took the system relief out of the equation so it may be your problem. Does the service manual state if the relief valve is pilot operated or show a parts break down for it? Pilot operated relief valves will fail open if the pilot orifice becomes blocked or a piece of crud gets caught on the pilot seat. Direct acting type relief valves rarely fail completely unless the spring breaks.

Hopefully this might point you towards the next step in diagnosis of this failure.

 

[shantie]

screen captures of the main 6 function valve bank and the left joystick showing pilot valve item 17. If I am looking at the schematic correctly the right travel would not be affected by the pilot valve operation.

thanks

 

[oldnslo]

You are correct the pilot pressure would have no effect on the travel function but item 1 the main relief being stuck open would unload the pump flow for all of the functions. Since sudden failure possible a spring broke, O-ring failed, if pilot operated relief could also have crud blocking pilot orifice.

 

[shantie]

I will look into this and let you know the results

 

[shantie]

We tested the pump pressure on pump 2 no pressure building, looks like a pump rebuild is in my future

 

[oldnslo]

Per the schematic pump 2 should have no effect on the right track but would affect the left track. Did both tracks stop working?