M1084A0 Crane Stalled

[firefinder]

I replaced some of the hoses on my M1084A0 Material Handling Crane. Lost about 2.5 gallons of hydraulic fluid during the hose replacement process. I was impatient and tested the system without refilling the reservoir. All systems worked fine until the boom extension and lift cylinders seem to stall. The other crane control components seem to be working well.

Attempted to search prior threads for this scenario without success. Given my feeble knowledge of hydraulic systems, I did not find any remedies in the tech manuals either.

Do these cylinders have pilot control valves at the cylinder base? Is it possible the pilot has lost prime due to the low fluids from replacing the hoses? If so, what is the best way to re-prime?

Stay safe and stay in touch,

firefinder

 

[snowtrac nome]

might be air not wanting to push through load holding valves

 

[firefinder]

I agree snowtrac.

TM-9-2320-366-34-3, Section 16-7, Page 271, discusses removal of the hoses from the counterbalance valves. But, there is no discussion of bleeding. The only instances in the tech manuals I find of bleeding is in the fuel system. Nothing in hydraulics.

The hoist motor control valve parts diagram is detailed in TM-9-2320-366-24P-2, Figure 381, Page 1228. The other cylinder control valves are part of the cylinder body and detailed in those diagrams. All of the individual parts are broken out, but the valve housing is shown as part of the cylinder.

I figured this was so simple, to the more hydraulically minded than I, that they didn't even think to include in the tech manuals!

What's the best method of clearing the air through the valves? Simple as loosening the hose / tubes to allow the air to bleed or other techniques required?

 

[FloridaAKM]

You have to bleed the hoses as a hydraulic pump cannot move air, it just cavitates. My experience is just loosen & bleed the hoses that you replaced till you remove the trapped air pockets. After that, you should be back in business! YMMV.

 

[oregonfirefighter]

Could there be air in your stabilizer jack lines? Perhaps a sensor is not recognizing that they are extended and in place? Most consumer lifts will not work unless all the supports are fixed in place.

 

[snowtrac nome]

the load holding valves in your cylinders have a screw you loosen up to allow fluid flow. once you have done that just extend and retract all cylinders through their full stroke. the pump is below tank level it will have a positive pressure on it no bleeding necessary

 

[firefinder]

Thanks for the follow-up!

 

[scottmandu]

I've replaced all the hoses on My 1084A1 and never had an issue with air in the system or bleeding.