Loader curl leak down

[CalG]

There is no need to turn positive enquiry into a negative. No one said that a properly functioning piston seal was not part of any effective repair. Some readers may find value in bringing out the truth of the investigation into "The case of the unaccounted volume". Similar symptoms may be associated with other difficulties.

 

[lexluther]

Pulled the cylinders and hung them from the rafter. With the cylinder compressed, plugged the same inlet on both. One cylinder holds my weight the other won't hold its own weight.

Have both rebuilt?

 

[CalG]

both are out, It will never be cheaper.....

 

[lexluther]

both are out, It will never be cheaper.....

Getting them out is free, except for the mess...lol, is there a secret to not making a mess?

 

[CalG]

Getting them out is free, except for the mess...lol, is there a secret to not making a mess?

Larger drain pans ;-)

 

[kennyd]

Have both rebuilt?

Like tires, brakes, wipers, headlights and even socks I feel it's always best to replace the cylinder seals in pairs. The "good" cylinder has cycled the same number of times as the bad one.

 

[Rocky J]

Lexluther this video is entertaining as well as educational and it might be what CaIG is talking about .:licking: How To Rebuild a hydraulic cylinder FT: georjah ja - YouTube

 

[LD1]

CalG: Let me try again here

The curl cylinders operate just the opposite as lift cylinders.

Lift cylinders on the loader hold the load by preventing the cylinder from being compressed. In order for the the loader to drift, cylinder rod needs to enter the cylinder barrel. And the ONLY way it can do that is for it to displace fluid OUT of the cylinder barrel. IE: external leak or back through the valve.

BUT, the same logic cannot apply to the curl cylinders, because they are trying to resist tension. They are trying to resist the rod leaving the barrel.

With the forces trying to extend the cylinder....pulling the rod out of the barrel, creates MORE volume inside the barrel of the cylinder. In a good working cylinder, with good gland and piston seals, the fluid on the rod side of the cylinder is contained by those seals. Not allowed to go anywhere, thus no movement.

With faulty piston seals, the oil can simply bypass the piston, and continue to occupy its "space" within the cylinder body, just on the other side of the piston. When you are extending a cylinder, you are creating MORE room for oil on the base-side, than you actually are displacing on the rod side. This will cause a vacuum. Gland seals and QD's are typically not designed to seal against a vacuum. And even if so, vacuum acts more like a "gas" or air, in terms of being "compressible".

So when it comes to having a cylinder "drift".......the biggest thing to look at is weather the "drift" is causing the cylinder to collapse, or to extend. Assuming NO external leaks, and its a simple circuit with just a valve and cylinder......if the drift causes the cylinder to collapse, it 100% CANNOT be the cylinder at fault.

But drift causing extension of the cylinder....could be either. The OP was 100% correct in his troubleshooting. Isolate the valve and cylinder by unhooking the QD's. IF problem is still there.....its the cylinder. IF problem stops......its the valve.

 

[CalG]

LD1

Very good explanation.

For myself, I had that covered in a single line of my earlier post. i.e.
"Of course the cylinders could be sucking air as they extend. That would make the explanation easier. ;-) "

 

[lexluther]

Confused by the hydraulic shops previous test result indicating the cylinder was good, I was about to give up and call a mechanic but decided to give it one more try with Google which is where I came up with the idea to disconnect the lines. Threads like these saved me have saved me hundreds of dollars which I will surely plow into more tractor accessories, guns or ammo, so thank you!

I am still not convinced it's wasn't sucking air somewhere, but it seems like anyplace that sucked air would also leak oil. There was some oil at the QD but not much. I'll get it all put back together and give it a bath and see.


Hilarious video Rocky, looks like my shop except I like to wear my white dress shirt and listen to Merle Haggard.

I will drop the cylinders off for rebuild today and come back with an update after rebuold.

 

[LD1]

LD1

Very good explanation.

For myself, I had that covered in a single line of my earlier post. i.e.
"Of course the cylinders could be sucking air as they extend. That would make the explanation easier. ;-) "

Maybe I read into it wrong, But I was still thinking things were unclear. Just trying to provide a little more detail/clarity to just whats going on. As long as everyone is on the same page :thumbsup:

 

[lexluther]

Here is the resolution




Got it all reassembled and got a nail in the tire immediately after on the way back from using the pressure washer on it. Oh well now it's put away clean and ready to roll next time the beaver makes our road impassible.
The first pic shows the parts that were clearly bad, the second shows the final bill to rebuild two cylinders ($260) and all the parts replaced.

The guy who did the work said there was a bit of rust in the cylinder that he honed, that seemed odd, but a long time heavy equipment contractor said this guy was the best.

 

[kennyd]

Thanks for the update Lex, glad to hear it was indeed the seals.

Now that you have the o-ring sizes, you can do the rebuild next time yourself :thumbsup:

 

[lexluther]

Had to repair beaver damage to the road again today, so i got my first seat time since rebuilding the cylinders... my problem seems to not be fully resolved... the cylinders clearly needed to be rebuilt, but I still have the leak down, just not as fast. I believe they hold when unhooked at the quick disconnect (QD). So I think my problem is the QD, hose to the valve or the valve itself. Based on thus excerpt from LD1, (the drift is causing the cylinder to extend) I am thinking (hoping) the QD is the culprit or perhaps a hose sucking air? I remember once they popped off when I was learning / digging.

Is there a way to tell, or do I just start replacing/ rebuilding?
Are the QD a repair or replace item?
If it's the valve, do you repair or replace?

Thanks!

...With faulty piston seals, the oil can simply bypass the piston, and continue to occupy its "space" within the cylinder body, just on the other side of the piston. When you are extending a cylinder, you are creating MORE room for oil on the base-side, than you actually are displacing on the rod side. This will cause a vacuum. Gland seals and QD's are typically not designed to seal against a vacuum. And even if so, vacuum acts more like a "gas" or air, in terms of being "compressible"...

 

[CalG]

Crap!
It get's more troublesome when the other guys fix doesn't work for you.

First, suspect the rebuild , the only useful verification is to isolate the components and make methodical checks.
Wrap the QD in an oiled plastic wrapper and see if it sucks in and ruptures.
A pressure gauge that can be moved from port to port, fitting to fitting etc. can help, but it's going to be messy. ;-)

 

[LD1]

It's the valve. The hoses and qds aren't gonna suck air. Under operation, it's a 2500psi system. If you had issues, it would be spraying oil.

Valves don't have seals. It's a metal on metal mating surface between the spool and valve body. Thus a little leakage is normal.

How much leakage is acceptable is all up to the mfg and their manufacturing tolerances. They usually list a spec as to how many ounces/milliliters per minute at a certain pressure is acceptable. Without knowing that spec, and translating that in to how many inches per minute the cylinder will move as a result, we cannot say if what you are experiencing is considered normal/acceptable

 

[lexluther]

Crap!
It get's more troublesome when the other guys fix doesn't work for you.

First, suspect the rebuild , the only useful verification is to isolate the components and make methodical checks.
Wrap the QD in an oiled plastic wrapper and see if it sucks in and ruptures.
A pressure gauge that can be moved from port to port, fitting to fitting etc. can help, but it's going to be messy. ;-)

The other guys fix was clearly partially correct if you read my prior posts.

So, is the valve rebuilt or replaced?

 

[CalG]

The other guys fix was clearly partially correct if you read my prior posts.

So, is the valve rebuilt or replaced?

Due to the internal clearances (very small) typical two or three spool valves are not rebuilt, just replaced. $200-$500
"depending".

 

[CalG]

The other guys fix was clearly partially correct if you read my prior posts.

In some circles that is termed "necessary, but not sufficient". That is why I encouraged complete understanding in my earlier responses to your troubles. Many times "just getting it done" is a temporary satisfaction. Sometimes it works out fine.

One "test" you might do is to support the FEL with a down tilted bucket and then letting the boom float. This will demonstrate if the leakage goes both ways. (perhaps showing as fluid , so clean everything well first.

Most valve leakage stays internal with the fluid going back to tank unobserved. pulling the return to tank line would show any leakage across the valve spools, but ANY movement of the controls would flood the return circuit and make for a confusing evaluation.

 

[lexluther]

So I tried to determine if it was the valve.

The problem is the same with all the QD disconnected. So I think the valve is fine.

To give you an idea of the speed of the leak down, it takes about 15 seconds to go from full up to full dump.

Still no oil leak visible, which makes me think it's sucking air, I can hear noise in or by the cylinder while it leaks down.

I wondered if it leaks up or maybe that would cause a visible leak. raised the front of the bucket by extending the curl see photo... **** thing seems to hold. I couldn't disconnect the QD under that pressure, so I'll leave it up overnight, I guess theoretically it never spends much time with a load on this direction.



At one point I pressed the nipple on the disconnected QD and got foamy oil from the side that should have sucked which would fit the sucking air by the vacuum from the cylinder extending. I replaced that QD to be sure.

Could the cylinder leak in just one direction even after rebuild?

Ugh