Haudraulic oddity that has my local dealer stumpped

[Logginsteve]

Before spending the money having my L3240 (5 years old) hauled to the orange doctor I wanted to see if anybody can help me figure out what is going wrong.

I have two circuits on my loader to operate a 72" grappler. I last used it in the Fall and took it off for the winter (such as we had here in Maine). I ran the tractor only a couple of times since then until yesterday. I drove it around and used the forks then switched off to the grappler. Plenty of power, drove as expected, nothing out of the ordinary.

When I put the power to open (bottom circuit) the jaw opens about one foot and then stops as if physically arrested. Up to the point it stops it behaves normally in terms of sound and responsiveness. Close (top circuit) works fine. No matter what I try to do, no change in behavior. I can see the hydraulic lines jerk when it hits the unexpected stopping point.

I switched the lines to see what would happen. The expected behavior was being able to open it full, but have problems closing. Instead it didn't want to move at all. Which is a mystery.

Today I pulled the couplings off the grappler to see how it moved manually. I could open and close it fully and easily. Further, the hoses (in a container) both bled out and sucked back in the hydraulic fluid. This indicates to me that the grappler is working perfectly OK.

Next, I replaced the male and female couplers for the bottom (open) circuit with brand new ones. Oddly it opens to exactly the same point as before (i.e. not where it should), but now the close function is sloooooooooooooow. Really slow. I swapped the female coupler on the top circuit and that made no difference.

Even though there were no signs of a loss of hydraulic power I did check the reservoir and I was down about 3/4 of a gallon. I don't know why, but I haven't checked it since last summer so I can't say when I lost the fluid. It doesn't seem to be a factor, especially because topping it off made no change.

Strange, isn't it? Anybody have any inspirational advice?

Thanks!

Steve

 

[massey driver]

if you have another cylinder/or ram hook it up to your tractor and see if it works.I suspect that you have something going on inside the cylinder.something has let go.bets would be to take it apart and see whats going on.Moving it in and out with no pressure isn't the same as what happens when it being pressurized.

 

[Billrog]

Change the hose that's causing the problem ?

 

[Mendonsy]

From your description it sounds like something is causing the return side from the cylinder to the tank to stop flowing. Are there any flow controls or check valves in the circuit??

 

[TractorTech]

It sounds as though you might have a restrictor hole in the base of one of the cylinders that is getting covered by a foreign particle like a piece of teflon ring off of one of the cylinder pistons. Not sure why the cylinder would stop at the same place, but manually actuating doesn't move the piece in place fast enough to cause blockage or noticeable flow restriction.
The easiest inspection, although may not reveal anything, is to remove the cylinder base hoses and inspect the cylinder ports. Next step would be disassemble the cylinders and inspect as massey driver says.

 

[Logginsteve]

Thanks for all the thoughts and advice. Good news is I fixed it, though I'm still not entirely sure what combination of things did the trick. Here's the details and hopefully there's something in it that can be learned from.

Yesterday I took both female couplings off the grappler and bled the fluid out as I checked to see if there was something physically wrong with one of the cylinders. It moved freely and burped out significant fluid. Since the original problem was sticking at about 6" opening I apparently only worked the jaw about a foot and declared it good (i.e. I didn't get stopped 6" out so cylinder wasn't the problem). But that was a mistake and late at night I realized this wasn't good enough.

Today I put a spare male coupling to the hoses in turn and tried to open the full range. It worked, but in the process there was a very large burst of AIR that came out of one of the lines. I mean big and all at once. As soon as that happened the jaw easily opened to its full position. I hooked it back up and sure enough it works fine now.

I confirmed with my orange doctor that the system is designed to self bleed, which is why neither of us thought of that possibility yesterday. Yet in my case something interfered with that and an air pocket apparently prevented full actuation. Now that it's clear I'm back to where I need to be AND I didn't spend an arm and a leg in the process. Just a couple hours of head scratching.

The lesson here is don't rule out the possibility of an air pocket when you run out of likely suspects.

Steve

 

[Logginsteve]

Not sure why the cylinder would stop at the same place

This is the part that had both the expert and me puzzled the most. All kinds of things can affect power or stop the flow completely. But it really should be either full stop no action or SOME amount of action, even if erratic, slow, low power, etc. Stopping at the same point every single time just didn't make sense except for an air pocket. Which itself doesn't make sense because air pockets, if they form at all, should bleed out as you actuate. Again, maybe erratically, however it should work its way out.

At least that's my layman's understanding of a closed hydraulic system with self bleeding capabilities.

Steve

 

[Billrog]

Good for you pleased it's up and working again :thumbsup:

 

[KennyV]

It won't be air causing the abrupt stop... air is compressible and acts like a cushion, and with 2500 psi it compresses a lot. Plus while compressed it's area of displacement will get small and easily travel out along with the fluid... You may be working fine for some reason now, but if you didn't locate the blockage,sorry to say it will likely return. KennyV

 

[Billrog]

I think what may have happened if there was a lot of air in 1 cylinder the other one was getting ahead of it locking it up. Never seen it happen with a tractor but fix this scenario with a friends motor home slide one side was leaking fluid so when he tried to activate the slide it would bind sideways and not go all the way.