Loader Valve Leaking Down

[rScotty]

There is a way for the piston seal to cause leak down without going through the spool. If you have the loader up and you shut the engine off then lower the loader part way now you have a void on the rod side, same can happen with the engine running if the loader is lowered briefly before the rod side can be filled. You can prove this by lowering the loader to the ground and keep the lever in the down position there will be a delay before it starts to lift the tractor up. Because the rod side has space. So I don’t agree the rod side is always full, because it isn’t.

Hmmm.... If lowering the arms without the engine running creates a void, wouldn't that put the void on the cylinder side of the piston instead of on the rod side?

On your second point, I"ve felt that delay too. But I don't think that the fact of a delay proves that the rod side is filling up an air space. Or even that there is an air space to fill. The delay could just as easily be in the time to take up slack in the loader joints and expand all the pressurized parts and hoses.

I do agree that we can set up special conditions like turning the engine off or reversing stresses and get some oddball loader effects. You've mentioned a couple of interesting ones.
But the original question was simply - What would cause the loader arms to drift down while using it?
I still think that it is most likely to be internal leakage in the control valve.

rScotty

 

[Seven Gables]

Hmmm.... If lowering the arms without the engine running creates a void, wouldn't that put the void on the cylinder side of the piston instead of on the rod side?

On your second point, I"ve felt that delay too. But I don't think that the fact of a delay proves that the rod side is filling up an air space. Or even that there is an air space to fill. The delay could just as easily be in the time to take up slack in the loader joints and expand all the pressurized parts and hoses.

I do agree that we can set up special conditions like turning the engine off or reversing stresses and get some oddball loader effects. You've mentioned a couple of interesting ones.
But the original question was simply - What would cause the loader arms to drift down while using it?
I still think that it is most likely to be internal leakage in the control valve.

rScotty

No , absolutely on the Rod side. If the pump isn’t filling the rod side as fast as gravity is bringing the loader down and
Rod into cylinder... there’s going to be a void on rod side.

 

[rScotty]

No , absolutely on the Rod side. If the pump isn’t filling the rod side as fast as gravity is bringing the loader down and
Rod into cylinder... there’s going to be a void on rod side.

Right, I see how you are viewing it now. in that case I agree that a void could be created on the Rod side if a heavy load collapses the cylinder faster than replacement fluid is being supplied.

To avoid that happening, many - but not all - control valves have the capability to add deal with that problem by using regeneration. Regeneration allows some of the fluid being forced out of the compression side of the cylinder to be diverted to the extension side. That adds the regenerative flow to the pump flow to offset low from the pump alone. Or just for increased hydraulic efficiency.

I don't know what type control valve the OP's TC45DA uses, regeneration is normally shown on the hydraulic schematic of the control valve circuit.

rScotty

 

[LD1]

Wow, another valve vs cylinder loader drift post. HAvent seen one of these in awhile.

But its very clear that a lot of people (even those so called mechanics or dealership employees) have no clue about hydraulics, and just regurgitate the bad information they have heard all their lives.

Lets put it VERY simply......the loader cylinders will NOT drift down (compress) unless oil LEAVES the cylinder. Either a leaky hose OR back THROUGH THE VALVE. PERIOD. END OF STORY.

Listen to oldnslo. He knows what he is talking about.

Bad cylinder seals will make a bad valve worse. And rebuilding the cylinders will make the issue less aparent....probably why everyone seems to preach about rebuilding the loader cylinders. But the root cause of the problem is the valve. You could rebuild the cylinders with NO piston seals and if the valve is good it still will NOT LEAK DOWN

 

[rScotty]

Wow, another valve vs cylinder loader drift post. HAvent seen one of these in awhile.

But its very clear that a lot of people (even those so called mechanics or dealership employees) have no clue about hydraulics, and just regurgitate the bad information they have heard all their lives.

Lets put it VERY simply......the loader cylinders will NOT drift down (compress) unless oil LEAVES the cylinder. Either a leaky hose OR back THROUGH THE VALVE. PERIOD. END OF STORY.

Listen to oldnslo. He knows what he is talking about.

Bad cylinder seals will make a bad valve worse. And rebuilding the cylinders will make the issue less aparent....probably why everyone seems to preach about rebuilding the loader cylinders. But the root cause of the problem is the valve. You could rebuild the cylinders with NO piston seals and if the valve is good it still will NOT LEAK DOWN

Thanks, LD1. Nice summary.

 

[Dman1981]

That’s amazing but it would leak up

 

[LD1]

That’s amazing but it would leak up

Not sure I understand?

 

[Dman1981]

Not sure I understand?

With no seals on piston putting down pressure loader would leak
Because rod oil
Would be displaced in head where there is no oil

 

[LD1]

With no seals on piston putting down pressure loader would leak
Because rod oil
Would be displaced in head where there is no oil

Yes there would be no down pressure with no piston seals.

I was just illustrating a point and not trying to muddy the water.
The simple point is cou cannot COMPRESS a hydraulic cylinder unless oil LEAVES the cylinder.

 

[dieselscout80]

I have not done any other troubleshooting on the issue.

However, I thought about some other things that I have noticed. If I park the tractor with my pallet forks so the tips are on the ground the next morning the back of it is now on the ground leaving the tips up (enough to trip on)

Another is when I hauled my tractor Monday it was loaded so the bucket edge was vertical. When I picked it up it flopped a bit before curl up.

The last thing is the owner before the guy I bought it from was a feed store and I am certain the loader was used a bunch as the bucket was worn.

The tractor had 1130 hours on it when I bought it and now has about 1200 hours on it now.