cat 430d loader lift hydraulics dead

[x6m]

RE: Caterpillar loader/backhoe 430d bnk05975

Hi folks,

I just experienced a sudden failure of the loader lift and bucket valve [mechanical type] to actuate anything; nothing on the lift arm moves at all. Everything worked fine when I shut it off, then, upon restart it’s like the lift arm is stuck in the float position regardless of the position of the valve handle.

The engine starts and runs fine, and the other hydraulic functions [steering, backhoe functions, and stabilizers are unaffected and functioning normally.

There are no hydraulic leaks. Seems unlikely that it is a hydraulic malfunction; more likely an electrical issue. There are 2 wires connected to a sensor, switch or solenoid at the base of the valve bank . I tested it for continuity and it appears closed. What is the function of it? Can anyone walk me through a troubleshooting sequence for it?

 

[Mark250]

I am assuming you mean this electrical connection.
it is part of the return to dig feature in the tilt control valve with mechanical linkages

 

[Mark250]

As the controls are mechanical for the loader it wont be an electrical problem
I would check the orifice and the resolver in the steering priority valve

 

[Dave Neubert]

Normally its the O rings on the resolver bottom out a function on the back hoe and move the loader lever at the same time and see if it operates

 

[x6m]

Hi Dave and Mark
Thanks guys for taking the time to help. Not easy to wrap my septuagenarian brain around these hydrodynamics. I also reviewed the other threads regarding a similar problem.
When I tested the loader end while actuating the backhoe end, everything returned to normal and I have not been able to replicate the failure event. Yet! Is it possible a small obstruction occurred in the sensor system and then cleared???
Clearly I am going to have my work cut out for me.
I’ve got the manuals but they cover so many machines and valve variations that it is hard to identify the components of mine.
The manuals I am using are:
renr3583-04 systems operation
renr3584-04 testing and adjusting
renr3585-02 disassembly and assembly
sebp3996 parts
any direct reference to pages would be helpful

Dave,
Maybe there are some typos in your reply. Can you clear up for me what you mean by:
“The O rings on the resolver bottom out a function on the back hoe” which resolver are you referring to? And where is it located?

Mark,
When the loader valves were dead the steering still worked. Can the ‘steering priority valve’ the ‘SMU’ in the schematic intermittently malfunction?
In the parts manual, page 304, which of the parts should I order?

 

[Dave Neubert]

hold one of the controls let it bottom out the function and at the same time try the loader control wile the back hoe is held in the resolver is on the bottom of the loader control right next or partly under the cover for the spool I think its a flush allen plug
i just read that you did that and functions returned I would still pull the resolver

 

[x6m]

Hi Dave,

Thanks for the walk through. Now that I know how to get the bucket off the ground and the machine moving again if the fault re-occurs I don’t have the fear of getting stuck. I’ll pull the resolver when I finish the project I’m on and post the results.

Thanks again for helping me get up to speed