My FEL is bleeding down

[StuartDK45SE]

2013 DK45SE bought new in 2014, only 64 hours.

I thought I noticed the other day that my FEL wasn't where I left it several hours earlier. Today I took a measurement and came back three hours later and it had bled down 3 inches in that time. What is acceptable? I would assume as new as it is for it not to bleed down at all.

 

[davesl708]

That is pretty normal. The control valve does not have O rings or other seals other than very close tolerance between the valve body and the spindles.
Some bypass will occur under load.

 

[DK35vince]

Normal

 

[k0ua]

Yep, 3 inches in 3 hours or an inch an hour is well within normal. Some are tighter than others, and might bleed a little less than that, but they all bleed down some.

 

[J_J]

Just about all hyd will leak down, some will hold better that others.

Worn seals will allow the cyl to leak down .

Worn spools in the hyd valve could leak down.

You tractor dealer service dept will have the leak down tolerance for your machine.

Sometimes it is how much you can tolerate.

Is it a safety concern

 

[LD1]

As others mention, valve bodies have no seals. IT is a tight metal on metal tolerance and not 100%.

3" in 3hrs is likely acceptable. But call the dealer and ask.

Worn out seals in a cylinder will cause the loader to be weaker, but will NOT cause the loader to leak down UNLESS there is an external leak somewhere.

 

[J_J]

Can it be true that thousands are rebuilding their cyl to fix a leak down when it is the valve causing all the problem.

It just seems to me that a load placed on a leaking cyl will leak down. That load being the bucket and lift arms.

It does seem strange that people that rebuild their cyl don't have the leak down after rebuilding.

Few people on TBN have said that by replacing the valve that the leak down was stopped.

Same with the 3pt leak down. Few people are replacing their 3pt valves.

They all seem to do the cyl. Why is that.

Just saying.

 

[davesl708]

Those rebuilding the cylinders may well be solving a problem with leak down. Especially if the leak down occurs during operations. Cylinders do have O rings on there pistons and do wear out and leak by.
However, if you raise the FEL and shut the engine off some slow leak down will occur due to the spools allowing fluid to bypass. The spools are letting fluid from all three cylinders to bleed off pressure and the FEL lowers. If one cylinder has bad O rings the other cylinder will not be leaking down and support the bucket and arms. Rebuilding the worn cylinder will correct that problem.

 

[J_J]

Even though the valve spools will leak some due to metal to metal tolerances, There is a leak down rate in drops per min for that situation for the dealer to replace the valve.

Now, let me ask you whether you would replace a $50 set of cyl seals or a $300 valve.

Now consider this, if a raised bucket and lift arms is putting down pressure on the piston in a very good cyl, that would therefore accelerate the valve leak down rate, correct.

So what pressure do the dealers use to establish the leak down rate, a static situation or a dynamic situation.

You might not even notice the leak down when using the cyl, except if you can't make the cyl go into relief, then you know something is wrong.

So now, add a cyl with worn out cyl seals, raise the loader and add a shutoff valve in the base end of the cyl, do you think the lift arms and bucket will descend a certain amount until the pressure is equalized.

In a static environment with no pressure and worn seals, the piston probably will not move in a cyl.

I am so confused, but not really.

 

[LD1]

It just seems to me that a load placed on a leaking cyl will leak down. That load being the bucket and lift arms.


Just saying.

Only if the cylinder is leaking externally.

It does seem strange that people that rebuild their cyl don't have the leak down after rebuilding.



Just saying.

If there was an external leak past the gland nut, then yes a rebuild would fix this. Or possibly one more theory I will discuss at the end of this post.

Same with the 3pt leak down. Few people are replacing their 3pt valves.

A 3PH is totally different. The "rod" side of the cylinder is open to the case (tank). So a leak past the piston goes straight to the tank. On a loader, the leak past the piston would HAVE to go through the valve (which is closed) to get back to tank. So, if the valve is TIGHT and NOT leaking by, there is no leak down.


Now that theory I mentioned. It IS possible for the valve spool to only be leaking by on the rod side port. In that case, if piston seals are shot, then fluid can bypass the piston, and then bypass the valve spool and you have leak down. In this case, Rebuilding the seals will stop leak down. But so would a valve replacement.

I know this has been debated on here FAR too many times. It is simple hydraulics. With a properly functioning valve, any fluid that wants to bypass the piston seals STILL has no where to go and should not leak down.

You can completely remove the seals, raise the loader, and unhook the quick connects and it will stay up all day long.

 

[arlen4720]

Can it be true that thousands are rebuilding their cyl to fix a leak down when it is the valve causing all the problem.

It just seems to me that a load placed on a leaking cyl will leak down. That load being the bucket and lift arms.

It does seem strange that people that rebuild their cyl don't have the leak down after rebuilding.

Few people on TBN have said that by replacing the valve that the leak down was stopped.

Same with the 3pt leak down. Few people are replacing their 3pt valves.

They all seem to do the cyl. Why is that.

Just saying.

Like has been said many, many times before....if a cyllinder is EXTENDED, it can't retract without some oil leaving the cylinder. The volume of oil that has to exit the cylinder has to be equal to the volume of the rod that is entering the cylinder as it retracts. It's just that simple.
Many single acting cylinders don't even have piston seals.
Consider this: Fill a jar to the top with water, then shove a dowl into it. Does the jar over flow? Is the volume of water overflowing equal to the volume of rod that was inserted?
Next put a tight lid on the jar, and put a hole in the lid, with a nice tight fit to the dowl. Do you think you could shove the dowl down into the jar with it full of liquid? Would it be safe to say that if the dowl moves down into the jar, that water would have to come out of the seal around the dowl?
Would it be safe to also say that if you have an extended hydraulic cylinder full of oil on both sides of the puck, and both ports capped, that the rod could not retract into the cylinder without oil leaving the cylinder?

Bucket curl cylinders and 3 point cylinders are different in the way that they are typically arranged on the machine, in the fact that they RETRACT to lift, so the load and gravity are trying to extend them. As the rod extends in a cylinder with bad seals, it creates a vacuum on both sides of the puck. Since the seals are bad in this example, you really have one chamber. The rod seals are not effective at sealing a vacuum and air is pulled in to make up for the volume of the rod as it leaves the cylinder.
I will challenge anybody to refute this logic. Also, I invite anyone with a settling loader boom to unplug the quick connects. As sure as the sun will rise tomorrow, that boom will not settle any further; of course I am stipulating that there is no external leakage of oil in the system.

 

[LD1]

Like has been said many, many times before....if a cyllinder is EXTENDED, it can't retract without some oil leaving the cylinder. The volume of oil that has to exit the cylinder has to be equal to the volume of the rod that is entering the cylinder as it retracts. It's just that simple.
Many single acting cylinders don't even have piston seals.
Consider this: Fill a jar to the top with water, then shove a dowl into it. Does the jar over flow? Is the volume of water overflowing equal to the volume of rod that was inserted?
Next put a tight lid on the jar, and put a hole in the lid, with a nice tight fit to the dowl. Do you think you could shove the dowl down into the jar with it full of liquid? Would it be safe to say that if the dowl moves down into the jar, that water would have to come out of the seal around the dowl?
Would it be safe to also say that if you have an extended hydraulic cylinder full of oil on both sides of the puck, and both ports capped, that the rod could not retract into the cylinder without oil leaving the cylinder?

Bucket curl cylinders and 3 point cylinders are different in the way that they are typically arranged on the machine, in the fact that they RETRACT to lift, so the load and gravity are trying to extend them. As the rod extends in a cylinder with bad seals, it creates a vacuum on both sides of the puck. Since the seals are bad in this example, you really have one chamber. The rod seals are not effective at sealing a vacuum and air is pulled in to make up for the volume of the rod as it leaves the cylinder.
I will challenge anybody to refute this logic. Also, I invite anyone with a settling loader boom to unplug the quick connects. As sure as the sun will rise tomorrow, that boom will not settle any further; of course I am stipulating that there is no external leakage of oil in the system.

I have no idea why this is such a hard concept for some to understand.

 

[davesl708]

On a two way cylinder you can remove the O rings on the puck and the cylinder can be extended and retracted due to the lack of seal between the two ends of the cylinder. The fluid moves back and forth flowing around the puck.

If the FEL arms are raised and the O rings are bad fluid will leak by and the FEL will lower. The fluid is simply moving from one end of the cylinder to the other.
A good example of this is your power steering cylinder. If the O rings wear out the steering will feel like it is floating when you are driving for a short time due to the pressure equalization on both sides of the puck. As soon as the pressure builds on one side of the piston it will move and you can steer.

 

[LD1]

If the FEL arms are raised and the O rings are bad fluid will leak by and the FEL will lower. The fluid is simply moving from one end of the cylinder to the other.

The fluid can "try" to move from one side to the other. But since there is different volumes from rod side and base side, SOME fluid has to EXIT the cylinder somewhere for the cylinder to retract.

This can only be in the form of an external leak (hose, gland seal, coupler, etc); or from a spool valve leaking by letting fluid return to tank.

 

[arlen4720]

On a two way cylinder you can remove the O rings on the puck and the cylinder can be extended and retracted due to the lack of seal between the two ends of the cylinder. The fluid moves back and forth flowing around the puck.

Think about what you are saying here. The volumes are different on each side of the puck. How do you account for that?
In the case of the steering cylinder the valve opens pressure to one side of the cyllinder, and the valve allows the other side to go to tank. If the seals are bad, fluid just blows through and can't exert force on the puck. That is not the same as a loader boom settling with a static load when the valve is centered.
Read over the logic in my previous post, and think about it.

 

[arlen4720]

I have no idea why this is such a hard concept for some to understand.

I think they view us as the dumb ones:laughing:

 

[J_J]

Prince Hydraulics > Support > Loader Valve FAQ

 

[J_J]

That is not the same as a loader boom settling with a static load when the valve is centered.

It is not a static situation with a load on the cyl such as a couple of hundred lbs.

Just for the h*ll of it, take a syringe and remove the plunger and close off the needle end.

Now, cut the o-rings or remove the o-rings on the barrel and fill the tube with water.

Now press on the plunger and see if the fluid in the tube will pass to the open side of the syringe.

Do you think the water will transfer?

 

[arlen4720]

Prince Hydraulics > Support > Loader Valve FAQ

While that is useful information, it doesn't refute any of the points that I made. In fact, in step 7 it says to mark the boom cylinders and measure the amount that they settled, calculate the volume, and says that is the amount of oil leaking by in the valve. They don't mention that bad seals could be the cause.

 

[arlen4720]

It is not a static situation with a load on the cyl such as a couple of hundred lbs.

It is a static load in the sense that everything is at rest and pump pressure is not being directed to the cylinder. But, I feel you are trying to divert attention away from the simple principle that I'm trying to explain. If you agree with my logic great, if not, I would love to hear your logic on how you disagree.