FEL won't hold cylinders at fixed position

[Jwmaustin]

Just got a 2000 model JD 4600 with 460 loader. Lift arms, bucket, all cylinders seem to leak off and drop in about 15 minutes. Not sure what to search for in previous answers on here?

Thanks for input!

Bill

 

[J_J]

Worn cyl seals or worn valve spools.

 

[Jwmaustin]

Since curl, lift and backhoe cylinders all are affected doesn't that mean it's something common to all of them? I do see where you've suggested ways to check cylinders to others. I can do that but the fact that all cylinders seem affected makes me think there's a common leak path...makes sense right?

p.s. thanks for the quick response!

 

[J_J]

You have separate valves for the FEL and the BH.

You could have leaking relief valve, but there are two or three of those.

A leaking relief valve on the BH would not affect the FEL.

Only thing common to everything is the pump.

How old is the tractor?

When you have a good cyl and good valve, it should lock the hyd . Pump is not in the circuit.

Leaks down in 15 min, I would say something is worn out.

1999 - 2003 4000 Compact Series

At least 12 yrs old.

 

[Jwmaustin]

Good logic. I think I follow. So I can check the cylinders for leak down by hose removal or swapping as I've seen mentioned. BH seems a little slower leak but all go down within an hour...FEL drops as I carry a load even. The tractor has 750 hours which doesn't seem like much and it's a model year 2000. I guess it's possible there are multiple seals that are bad, I just wondered about one point common to FEL or BH. Sounds like I can check the relief valve for FEL and relief valve for BH if I understand your comment. I think I'm beginning to understand....seems scary LOL

You've helped a lot.

 

[Tx Jim]

J_J
Please don't take offense as I'm just asking a question.
If the boom cyl rod end is attached to loader mast and butt end is attached to boom corresponding to JD 460 FEL photo I viewed and assuming cyl packing is blown where does the displaced oil go if piston moves toward butt end of cyl because the rod occupies space in cylinder where oil must occupy? Won't more oil have to be displaced than cylinder bore has volume because of the area the rod occupies which gets greater as cylinder closes? I think control valve spools or it's relief valve would be the boom leak down problem not the lift cylinders.
Thanks,Jim

 

[J_J]

That is absolutely true.

Any movement will stop when the pressure equalizes.

The relief valve is not in the circuit when the lever is in neutral.

This is what he said.

{ Lift arms, bucket, all cylinders seem to leak off and drop in about 15 minutes ]

With only 750 hours, it would not be logical that all cyl leak down. However it could be one cyl in each circuit.

Best gress would be the valve spools tolerance is not that good.

You do know you can use a manual hyd pump to check a cyl or a valve.

Are we back to the cyl can't leak down thing?

 

[bigdeano]

I agree, it's most likely worn valve spools. My old backhoe had that problem. Are you sure the 750 hours is accurate? That's only 50 hours a year for 15 years. Maybe the hour meter was replaced.

 

[Jwmaustin]

The guy I purchased from is someone I know. I think I can trust his statement on the tractor hours (it looks like 750) but I guess I never asked if he purchased the loader separately. The loader itself does have more wear than the tractor. I was assuming like you guys that 750 is low hours. I'll check with him tomorrow.

Yeah I should have been more clear in my post too. It sounds like the control valves need checked for hoe and loader. The relief valves only are involved when pump is in the circuit, right?

But if it's the loader control valve that's typically a part of the tractor isn't it? When I bought the 300cx loader for my JD4300 it had a loader valve pre-installed so it was "part of the tractor". Do you think someone would have purchased a used loader AND a used valve? Again I'll ask, in fact I just sent an email to him.

Thanks for the help...these forums are like having several buddies working around the garage.

 

[LD1]

If leaking down causes the cylinder to compress, then it is not worn packing or anything to do with the cylinder. The problem is elsewhere like the valve. That is assuming the oil is not leaking externally.

IF leaking down causes a cylinder to extend (like curl) then the issue could be cylinders OR valve.

For the FEL, raise it up about 16" or so and put a jack under it. Rest the loader on the jack and remove hoses (assuming you have QD's). Now lower and remove the jack and see if it bleeds off. You will need to put the jack back under it to take the pressure off the hydraulics in order to hook the QD's back to the tractor