John Deere 146 Loader Leaking Off

Hello everyone. I've got a John Deere 2640 with a 146 loader. The loader is plumbed correctly into the pressure control valve and returned into the filter housing. I have the original two spool loader valve that operates the loader. With the tractor turned off and loader raised, it doesn't take long for both the lift and bucket to leak off. My loader is plumbed with quick couplers at the pressure control valve and filter housing. With the tractor turned off and the loader lifted, I disconnected the return line and the loader will stay up all day like its supposed to. As soon as I plug the return line in it immediately begins to pop and creak as it slowly leaks off. The final test I did was putting the loader all the way down and disconnected the return line. I held my finger over the fitting to open the valve on the on the end of the return line. When I cranked the tractor the return line immediately pressurized and I could not depress the valve. Pretty sure that oil is constantly returning back to the filter housing. I read here that this should not be the case when the loader is not in use. I am thinking that there is something wrong with the loader valve itself. Am I on the right track? Can it be repaired? I've read in several places that the valve often cannot be repaired. I've also attached a photo of the bottom of my valve just to make sure that I have the pressure and return lines hooked up correctly. The one with the red circle is the return line.

Thanks!

If you had the pressure and return lines backwards the loader would not work. The valves would suck all the way in one direction and you would not be able to recenter them.

It's likely the valve is leaking internally. It's probably not repairable, as these valves rely on the lapped steel-on-steel fit of the spool and body to provide a seal. O-rings are only sealing between the valve and the outside world. Decades of cycling the spools back and forth have worn both the spools and their bores.

It's the Cessna two spool valve.

I think barnyard is right on the money about your valve leaking by and letting the loader cylinders settle. The rest of my points do not change this. The valve no matter the type passes fluid when you operate it and then when centered holds that fluid from passing back or captures it in the hose and cylinder. You say you have an ..original.. spool valve. You mean it is an original valve JD would have sold for that loader? I am just wondering if the valve may be an open center valve instead of the correct closed center valve I think that is correct for your tractor. On second thought I believe a 2640 may be a closed center or open depending on the serial number. Has the loader and valve been on the tractor and operating fine or is this a recent install. The response of the return pressurizing means it is an open center system or you have an open center valve on a closed center system.

The loader is original to the tractor but has been operated since 1977 off of the rear remotes. Several months ago I bought the cessna two spool valve and bracket from a john deere dealer. It came off of a tractor equipped with a 145 loader. Is there a way to tell if it is an open center valve? Surely its not, but maybe so! Loader operation is good. At low RPM when tractor is hot there is just the slightest hint of chatter but clears up with increased throttle. I've attached the best picture I have of the valve, although you can't tell much due to the bracket.

You could still have leaks across either one or more of the valve spools, acrosss one or more of the cylinders pistons, or both.

The fact that the loader only drifts down a little and then stays in position when the hoses are disconnected from the tractor only means that the incompressible hydraulic fluid trapped in the loader has run out of places to flow and the pressure has equalized across all the valves and across both sides of all the cylinders.

A good example of this is taught in most beginning hydraulics classes.
1. Connect both ends of a cylinder together with a hose with a pressure gauge.
2. with the rod end up, place a weight on the rod.
3. the pressure on both sides of the piston will increase and equalize at a rather high pressure equal to the weight over only the cylinder rod. The bore of the cylinder no longer has any effect, only the weight and the rod size matter.

..Is there a way to tell if it is an open center valve? Yes, disconnect the pressure in and return line, blow in the valve inlet if air blows through it is an open center valve. Sounds like you are saying your tractor is closed center.

(quoted from post at 08:17:30 06/22/22) It's the Cessna two spool valve.

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Have a look at the''load checks'' (key #5) and the springs, (Key #4) for wear, damage or trapped debris.

I assume you have the valve hooked up the ''standard'' way, pull rearward to raise, the load checks only work if it's set up like that.

I'll give that a check. And yes, the valve is set up the correct way.

One other thing that I thought of that might be worth mentioning. When the bucket has a heavy load in it, I've noticed that when
I dump the load, the bucket stops midway and pauses before continuing its cycle for full dump. Sometimes it acts like its wants
to reverse directions. I've read some on here about regen, but I'm fairly certain that my valve is not equipped with this.

To add, to test the cylinder packings for certain place a quick coupler set in the lift side of the circuit of the loader frame lift cylinders. Raise the loader up and place it on something solid 6 off the ground. Let pressure off and uncouple back away and if it stays up the cylinders are good. Repeat with bucket curl cylinders. Probably easy enough to figure out but in both cases angle the bucket so you can drive back up on the item to take the pressure off to recouple the hose. A for certain leak free shut off valve would do the same and you would not have to worry about setting it on something. This does only check them in one certain position but usually a failed packing leaks in almost any position. Only possibility to leak in one position but not another would be scoring in the cylinder bore.

I should have mentioned that all of the cylinders were rebuilt recently. Pretty sure that the cylinders are in good working order.

You are correct. No way a cylinder can retract with both hoses disconnected on a regular double action cylinder where piston end is holding oad.

Also, no way for oil to escape out the return line with loader raised except past the internals of the cylinder.

Buckets are different on most loaders as they hold the load on the rod end of the cylinder so it takes a little more diagnostics to pin point the problem. The oil level would actually lower in return end , which would be piston end in that case. And it only takes one cylinder leaking internally of loader to effect loader and one cyl on bucket to to effect loader bucket.

One problem with John Deere, is that the piston packings are usually V Packings. These have to be installed pointed to the rod on boom cylinders. Pointed away from rod on bucket cylinders. John Deere use one set and for main direction use. I have had to turn packing in the right direction even after a dealer had repaired them. Was always a problem when a fellows wife would bring me a cylinder to repack. I had to find out if cylinder was used for lifting or on the bucket. Some bucket cylinders looked more like booms on some models

Fixed the issue with a new control valve. The control valve is a Cross Manufacturing SBA22CC closed center valve with Joystick conversion kit. Valve works flawlessly and loader no longer leaks off. Joystick is much improved over the old style double levers. Very impressed with Cross products. Thanks to everyone for their help!