How can I test a loader for cylinder vs control valve leakage??

[Tx Jim]

I'm with 4570Man

Simple "volume issue" You can put a liter of oil plus 1/2 liter volume of steel shafting into a 1 liter volume cylinder.

The oil must go somewhere!

DITTO

 

[BeezFun]

Do you have some way of supporting the loader a ways off the ground? If yes raise the loader, support it, unplug quick disconnect in the cap end of the cylinders. Remove the support, does the loader drift down? If yes you have bad seals on one or both of lift cylinders.

If no your valve is the source of the leak.

I believe there is one additional step necessary for this test to work properly. The total volume of fluid in the cylinder changes as the loader drifts down because the rod end contains the steel rod and fluid, whereas the cap end only contains fluid. So there has to be somewhere for the trapped fluid to go as the cylinder retracts. If the cap end is plugged, and rod end is attached to a valve that's not leaking, then the load can't drift down because it's trying to compress a trapped volume of fluid. This test would work if the rod end of the cylinder were open to tank, or some kind of collection container. So I believe this test will work if, in addition to disconnecting the cap end hose, the rod end connection is open to a container to capture the fluid that needs to escape as the cylinder drifts down.

 

[oldnslo]

I believe there is one additional step necessary for this test to work properly. The total volume of fluid in the cylinder changes as the loader drifts down because the rod end contains the steel rod and fluid, whereas the cap end only contains fluid. So there has to be somewhere for the trapped fluid to go as the cylinder retracts. If the cap end is plugged, and rod end is attached to a valve that's not leaking, then the load can't drift down because it's trying to compress a trapped volume of fluid. This test would work if the rod end of the cylinder were open to tank, or some kind of collection container. So I believe this test will work if, in addition to disconnecting the cap end hose, the rod end connection is open to a container to capture the fluid that needs to escape as the cylinder drifts down.

4570, CalG, & Tex Jim,
Please Go back to my post #11 and reread the last sentence in what I stated.

 

[Tx Jim]

oldnslo
Ok here's your statement & I'll quote you[/quote]By leaving the rod end hose connected you have a path for the oil to return to tank IF the piston seals are leaking.[/quote] IMHO not true if return hose is attached to a non leaking control valve.

 

[oldnslo]

oldnslo
Ok here's your statement & I'll quote you

By leaving the rod end hose connected you have a path for the oil to return to tank IF the piston seals are leaking.[/quote] IMHO not true if return hose is attached to a non leaking control valve.[/QUOTE]

Jim,
You are correct that if the valve does not leak the cylinder will not drift. Hind sight being 20:20 I should have included the valve must also leak in this statement. That would then point towards the valve leaking from the cap end being the initial problem all along.

This test was intended to isolate the potential leakage of bad piston seals and a leaking valve contributing to the cylinder (FEL) drifting down which was the OP's original question.. In my mind this is a very simple test to show exactly that potential problem.

 

[ch1ch2]

Youæ±*e making this too hard. Itç—´ impossible to push the rod into the cylinder without leaking oil past the valve or leaking externally.

That is correct and the most over look thing when bucket lower on their own. If the buck lowers it has to be a valve.

 

[daugen]

I'm sorry to ask a stupid question but i'm trying to follow this with limited mechanical ability.
The control valve being referred to is the valve external to the cylinder usually far away from it?

And...if I take 4570's cut to the quick approach, if I don't see oil leaking from the cylinder, not hard to check on...
then the problem is in the external control valve?
I know this has been covered but what about a worn out cylinder that doesn't leak externally but doesn't hold pressure properly internally?
I'm assuming that's when you need a "complete" test.

Thankfully you can "get to" most of this stuff and fix it without big bucks.
Took me a long time to figure out why my grapple was so hard putting on until I realized I had to unload the pressure from the FEL, first one
I had ever operated. What is the matter with that little ball? It just won't push in...

Clearly if one has been operating hydraulic lifts/equipment for forty or more years you just know what breaks all the time.
But I wonder if more modern equipment has other or newer problems.
Like the use of internal plastic valves instead of metal.
Or perhaps soon, pressure sensors on each ram. (I love instrumentation...)
Nice little gauge with six psi readouts, like a TPMS system for motorhomes.

I can leave a thousand pound mower on the three point of my Kubota and it will stay elevated in the same place for a week.
Not so for the front, need to remind myself to always drop equipment front and rear. I live alone so it's only my feet under there but...

If you look at the title of this thread, I think OP got a perfect answer to his question.

 

[b7610hsd]

Being as The loader has a Left and Right cylinder. Either both cylinders are leaking or just the one valve.

 

[hawkeye08]

I think I am finally understanding all this a bit.. my loader drops also so based on this thread, I expect I have a leaking valve. My tractor is lightly used low hour (<800hr) and the only abuse is back dragging to smooth out the ground when moving dirt around. My bucket also drops if I put a brace under the loader arms so the whole loader does not drop. It used to stay up with no drift a couple years ago. Are the loader valves easily rebuildable or is the fix replacement?

 

[Groo]

I think I am finally understanding all this a bit.. my loader drops also so based on this thread, I expect I have a leaking valve. My tractor is lightly used low hour (<800hr) and the only abuse is back dragging to smooth out the ground when moving dirt around. My bucket also drops if I put a brace under the loader arms so the whole loader does not drop. It used to stay up with no drift a couple years ago. Are the loader valves easily rebuildable or is the fix replacement?

I believe generally it is a spool replacement.

Putting in a PO check/loadholding valve might be another option if all you are worried about is the loader drifiting down.