Loader Boom Drops Before Lifting

pittstate08 · Dec 22, 2020

I have a New Holland L778 skid steer that the boom seems to go into a "float" stage and drops just before lifting (if I am trying to feather the lift it will drop clear down). The tilt cylinders work perfect and do not do this. I rebuild all cylinders on the machine and this did not help. Does anyone have any suggestions on what could be causing this problem and what needs done to remedy it?

ptsg · Dec 22, 2020

That seems to be the load check valve for the lift/lower circuit stuck open with trash or the spring broke.

Load check valves prevent exactly that symptom when lifting the loader.

There should be one for each spool and it's usually located in between the work ports of the loader valve block. Some manufacturers use a hex plug, other a slotted plug.

RickB · Dec 22, 2020

Agree 100%.

wdchyd · Dec 29, 2020

I would double check the lift cylinders before pulling apart the control valve, one piston seal can cause the load to drop when feathering if it’s bypassing.
If you can test them 100% then the load checks in control valve would be next.

RickB · Dec 29, 2020

wdchyd said:
I would double check the lift cylinders before pulling apart the control valve, one piston seal can cause the load to drop when feathering if it’s bypassing.
If you can test them 100% then the load checks in control valve would be next.

Removing a load check is easier than rebuilding a cylinder which the OP has already done. If the symptoms are tied only to activating the circuit, a faulty load check is most likely.

wdchyd · Dec 29, 2020

Pittstate08, can you swap the tilt hoses with the lift hoses at the control valve? This will show if it’s in the control valve or cylinders.

wdchyd · Dec 29, 2020

RickB said:
Removing a load check is easier than rebuilding a cylinder which the OP has already done. If the symptoms are tied only to activating the circuit, a faulty load check is most likely.

I’m not suggesting pulling apart the cylinders again yet, I’m suggesting doing troubleshooting before taking any components apart to isolate the problem first.
If it is his cylinders (from a bad repair) then they might come apart easier than pulling a control valve IMHO.

RickB · Dec 29, 2020

wdchyd said:
I’m not suggesting pulling apart the cylinders again yet, I’m suggesting doing troubleshooting before taking any components apart to isolate the problem first.
If it is his cylinders (from a bad repair) then they might come apart easier than pulling a control valve IMHO.

You wanted him to double check the cylinders, suggesting a failed seal could be the problem. How do you suppose he is to accomplish that without tearing the cylinder down? Would a failed piston seal cause the boom to drop when the operating valve was centered? Probably just as much as when the valve is stroked.
The troubleshooting is in the OP's post. The boom drops when he shifts the boom valve spool to the raise position. There is no indication or complaint of the boom drifting, creeping or having diminished capacity. The boom drops when the valve is stroked to raise it. For those here that understand how a load check works and what happens when one fails revisiting the cylinders is a waste of time. Now an L778 is an old machine and it's been a while since I've been close to one but I'll wager the load check can be removed from the valve housing right where it sits.

wdchyd · Dec 29, 2020

Rick ,I don’t know why you are arguing with me, I’m trying to help him like you.
He obviously doesn’t know how to troubleshoot properly or he wouldn’t t be here asking questions.
Yes, the cylinders can be tested without taking them off. He claims they were rebuilt but by whom and were they done properly?
If the loader lift piston seals were compromised it would do this exact scenario. With the control valve spool centered the cylinders would stay up till the spool was shifted as both ports blocked the cylinders would act like a single acting cylinder, when shifted to raise the load can go down, and if it’s excessive it won’t like to lift a load to capacity.

I’ve seen it happen many times.