FEL drops when engine off

[io540]

I am getting mixed messages. The bucket slowly drops when the engine is off. Is this more likely due to a cylinder problem. I see no evidence of fluid leaking. Or would it be the control valve? Help is greatly appreciated. To many "experts" here. Thank you.

 

[bcp]

Do you have quick connect hoses? If so...

Lift it, then time it and see how long it takes to drop about 6 inches.

Then lift it back to the same height, disconnect the hoses, and see if it drops at about the same rate. If it does, it is the cylinder leaking. If not, it is the valve.

Bruce

 

[cviola2005]

Both parts could be the cause of the problem. One cylinder could have a leaking piston seal (internal leak) and the other will leak through it, lowering the bucket. The control valve could also have a leaking seal (internal leak) that could lower the bucket.

The only method that I can think of to verify location of internal leak requires a way to support the lifted bucket, and removing and capping hydraulic lines, so let's wait for other's (more "expert"-like than myself) input, before we delve into that.

Edit: Good idea Bruce, my idea is the same, but I didn't think about quick connect fittings (brainfart moment).

 

[Hassman]

My bet would be on the valve leaking when pressure is removed from the pressure side (engine/pump stopped running) as it only drops after you switch off the engine/pump. Should be fairly easy to change the o-rings in the valve spool.

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[cviola2005]

My bet would be on the valve leaking when pressure is removed from the pressure side (engine/pump stopped running) as it only drops after you switch off the engine/pump. Should be fairly easy to change the o-rings in the valve spool.

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That sounds like a very solid point, good thinking!

 

[1970cs]

BCP has the right idea, with the quick disconnect couplers you can isolate the circuit. Then you cap each cylinder individually to see which one is causing the issue NOTE YOU MUST SUPPORT THE LOADER WITH A CHAIN FALL WHEN YOU PULL OFF ANY LINE, except the quick disconnects.

Valves can be the culprit! but more of the exception than the norm. As suggested above by putting in o-rings will not solve the problems unless there is an external leak at the spool( shiny part) the spool moves back and forth to open passages to control up/down or tilt down/up and when the spool is in the neutral position it returns the fluid back to tank. FYI spools are machined to specific tolerances to tightly match the valve body and cannot be replaced, except a new valve.

The likely culprit is the seals on the lift cylinder/cylinders or scaring of the barrel.

FYI you have a LA450A loader.

Pat

 

[RCW]

In my thinking, I'm wondering why it would be important if the FEL bleeds down when the engine isn't running. Now if it falls quickly, different story.

As one of the other guys asked, how quickly to drop 6 inches?

I equate it with the plumbing in my house. I turn the main water entrance valve off if we're away. No doubt, some faucets/fixtures in the house will drip a little. Since liquids don't compress, the pressure in the house plumbing pressure will decrease quickly over time without a pressure input. My input pressure is 95 psi, but I'd bet after a few days we're near 0 psi in the house, just due to VERY minimal leakage.

Same with your loader, pressure will drop and loader, too. It's just a matter of whether you have a lot of "faucet drips," meaning the seals or O-rings the guys are talking about, or just a little.

It's not a good practice to leave pressure on an hydraulic system for an extended time with engine off.

The mower deck on my little BX will bleed down a little if parked in a lifted position by my error. Done it since new, and I'm okay with that. It's expected. If I realize the deck is up, I put it down.

Better to just put everything down, and take pressure off the system by working the FEL valves in all directions after the engine is shut down.

Best wishes!

 

[Kennyd4110]

Define "slowly"? Some leakdown is quite normal, and most OEM's even publish acceptable leakdown rates.

 

[dfh1977]

My BX FEL does the same with the engine off. I can leave the FEL up and many hours later it is sitting on ground on its own. So with 6 inches it will drop slowly over hours on own. Sonwould i have a real problem and need fixed by dealer or just ignore issue as it is doing what i was told to do when done using was to always drop any fel and attachment on back of tractor.


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[lugbolt]

Kubota's maximum leakdown rate is 2" per hour, measured at the cylinder (pin to pin).

There is no pressure on the valve while the engine is running with this type hydraulic system. Pressure only builds when one of the spools is moved away from center.

Probably a leaking cylinder, internally. One or both. If it's less than a couple inches in an hours' time, you can rebuild it if you want to, but it's considered acceptable at 2" or less in an hours' time.

Usually if a spool leaks internally, it also leaks externally-as well as has other issues, while the engine is running. Not always, but more times than not.

 

[Hassman]

Please correct me if I am wrong (and this would not be the first time) but if the spool allows flow back to tank when in the neutral position then as soon as one were to take ones hand off the handle the whole FEL would drop to the ground.
-unless of course there are pilot operated check valves inline.

I am more used to hydraulic systems with constant pressure/variable flow (variable swashplate pumps as opposite to gear pumps) and I do realize that the valves are different for these two applications.

Also if the ram extends then a higher volume is needed as the back end of the ram has a larger volume than the front -where does this fluid come from?

Not arguing -just want to fully understand the system.
Cheers,
Hasse

 

[1970cs]

Yes, they use a poppet as a load check valve usually meant for when you first stroke the valve as way for it not to drop the load.

Pat

 

[jajiu]

I have the same problem with my L3560. I dropped the tractor off at the dealer for some service and to add a BH92 backhoe and told the service manager of my FEL lowering over time when the tractor was turned off and he said that is normal and there is no fix for it.

 

[CountryBumkin]

I don't like the idea of trying to disconnect a hose while it's under pressure. Chain fell or not. I think this is a bad idea. What if the quick disconnect is faulty.
The correct method would be to put a "hydraulic flow and pressure meter" in the line. A tool like this https://www.otctools.com/products/hydraulic-flow-tester. Then you can shut off the flow and see if the FEL drops.

If you don't have a hydraulic tester (and most people don't), take the tractor to the Dealer. One wrong move could kill you. Too many folks trying to save a buck or two really mess themselves up. I'm off my soap box now. Good luck.

 

[1970cs]

So tell me how a flow meter or pressure tester going to tell if you have cylinder packing leak by? This how we do it in our shop and that works to isolate the circuit.

Pat

 

[CountryBumkin]

So tell me how a flow meter or pressure tester going to tell if you have cylinder packing leak by? This how we do it in our shop and that works to isolate the circuit.

Pat

You put the test meter in-line (between control valve and the lift cyl.) with the FEL on the ground, no pressure, then start tractor and raise FEL. Then you can then shut off engine and close the meter's flow valve. If FEL starts to drop you know the problem is in the lift cylinder. (the test meter is just used as an expensive shut-off valve in this test). If the FEL doesn't leak down, then open the test meter flow switch and if the FEL starts to leak drown then the problem is in the control valve.

IMO, your shop method is fine for mechanics that are familiar for working around hydraulics and know what to expect. I'm just expressing concern about the "back yard mechanic" disconnecting hydraulic lines that may have pressure on them.

 

[Rolling Stock]

You can, while the FEL is down, relieve the pressure, disconnect the lines and install a couple ball valves inline and reconnect. Then you can lift the FEL and close the ball valves to isolate the cylinders. That way you aren't trying to disconnect while up and you can maintain control.

 

[CountryBumkin]

You can, while the FEL is down, relieve the pressure, disconnect the lines and install a couple ball valves inline and reconnect. Then you can lift the FEL and close the ball valves to isolate the cylinders. That way you aren't trying to disconnect while up and you can maintain control.

Yup.
If your tractor has quick disconnect fittings between control valve and FEL cylinders, you could make up a cheap tester with a "male disconnect on one side, a female disconnect on the other side, and a ball valve in the middle".

 

[1970cs]

You put the test meter in-line (between control valve and the lift cyl.) with the FEL on the ground, no pressure, then start tractor and raise FEL. Then you can then shut off engine and close the meter's flow valve. If FEL starts to drop you know the problem is in the lift cylinder. (the test meter is just used as an expensive shut-off valve in this test). If the FEL doesn't leak down, then open the test meter flow switch and if the FEL starts to leak drown then the problem is in the control valve.

IMO, your shop method is fine for mechanics that are familiar for working around hydraulics and know what to expect. I'm just expressing concern about the "back yard mechanic" disconnecting hydraulic lines that may have pressure on them.

Gottcha! But $3025.00 for that piece is out the window for everybody but shops that repair. He should just take it in to be safe. Or do the ball valve thing that some else has suggested.