Loader curl leak down

[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