419 Loader - Leaking?

[GONO2]

My loader on my 790 has always slowly leaked down, but lately it is much worse. Not only does the bucket slowly turn to dump (especially with a load in it), but the bucket goes down toward the ground as well. I had to raise and turn the bucket every 10 minutes while running the tractor yesterday. It does the same with the tractor not running too.

Any ideas on what is causing this and what needs to be done to fix it?

I also remember reading on here a long time ago about something you could do (shims I think) to get a little more capacity out of the loader. Anyone know the details? I can't find anything using the search feature.

Thanks for any help.

 

[RoyJackson]

First thing, check your hydraulic fluid level. Top it off, if necessary. If the level is OK, it's easiest to reseat your loader QD's.
If you still have a problem, change the fluid filter (personally, I'd change both the fluid and the filter).
If your loader still leaks down rapidly, it may be an internal leak in the valve body. I'm sure a rebuild kit (O-rings and other seals) is available. You just have to decide if you think you want to attempt it.
Or, learn to live with the leak down...until it gets bad enough that the leak down interferes with your work.

My loader (also a 419) doesn't leak down when the engine is running. Of course, I lower it before I get off the tractor most of the time....safety issue with me. Also,I don't let the tractor idle more then 5-6 minutes, so I may not even notice leak down.
I did see how long it took to leakdown with the engine off, one time. From about half raised to the ground took a few hours. Again, I always lower the loader for safety reasons, but I did try this experiment once.

As far as shimming the relief valve for more lift capacity, I have that information but I'll need to locate it. I'll post it when I find it. I did shim my tractor. It feels stronger, but I have no objective proof of a lifting capacity increase.

 

[kennyd]

There are two things that can cause your FEL to leak down. One is the cylinders and the other is the valve.

If it's the valve-then unfortunately there is no easy or cheap fix. The valve has NO internal wear parts that can be replaced. There are no O-rings or seals in it. The spools (the metal part that moves when you operate the joystick) is a precision lapped fit into the valve body and cannot be bought as a separate part. When the tolerance gets out of spec than the only solution is to replace the whole valve assembly. All of the valve used on CUT's are like this and can be expected to leak a little...JD even has a published document of "acceptable" leakdown times.

If it's the cylinder's, then they can be rebuilt with new seal kits. The kits are about $25 per cylinder from JD-or you could take them to a hydraulic shop and have them do it.

The best way to determine the cause is to raise the loader off the ground and rest it on something like a jack or pickup truck bed, then unhook the QD's from the tractor. Now remove the jack or pull the tractor away from the truck and observe the time it takes the loader to leakdown. Most likely the loader will still fall indicating the cylinders are bypassing internally.

Since think the problem has gotten worse recently...then I would assume the cylinders are your problem and not the valve. This is not unusual...

 

[RoyJackson]

If it's the valve-then unfortunately there is no easy or cheap fix. The valve has NO internal wear parts that can be replaced. There are no O-rings or seals in it. The spools (the metal part that moves when you operate the joystick) is a precision lapped fit into the valve body and cannot be bought as a separate part. When the tolerance gets out of spec than the only solution is to replace the whole valve assembly. All of the valve used on CUT's are like this and can be expected to leak a little...JD even has a published document of "acceptable" leakdown times.

Actually, there are a number of seals and o-rings in the valve body. The attachment is from the JD parts website.
I'm pretty sure the shop manual discusses rebuilding the valve...also the measurements.
You'd need the shop manual to rebuild...mostly for the spool's wear measurements

Kennyd's 4110 may not have a rebuildable valve...but the 790 does.

Good point about the cylinder internal leakage...something to check out.

 

[Willl]

First thing, check your hydraulic fluid level. Top it off, if necessary. If the level is OK, it's easiest to reseat your loader QD's.
If you still have a problem, change the fluid filter (personally, I'd change both the fluid and the filter).

I'm not following ya Roy, how would these items have anything to do with leak down ?

 

[Willl]

Actually, there are a number of seals and o-rings in the valve body. The attachment is from the JD parts website.

That pic shows no seals between supply and return ports.

Those o-rings shown are for valve shafts exiting the valve body.

 

[RoyJackson]

I'm not following ya Roy, how would these items have anything to do with leak down ?

When working on anything...take the least invasive steps you can first. Hydraulics depend upon fluid pressure and capacity(volume is probably a better word). Low fluid levels can result in lower performance. If there is a restriction in the flow (cruddy filter), that would also reduce preformance.
Is that what's happening here? No idea..but checking these items could prevent a more expensive, and perhaps unnecessary, tear down of a component.
Make sense?

That pic shows no seals between supply and return ports.

Those o-rings shown are for valve shafts exiting the valve body.

Read the two posts again. Kenny stated there were no seal or o-rings in the valve....there are. If the body is torn down to measure the spools, you'd want to replace them. It's be nice to have a schematic on hand to see the flow... However, there are multiple seals so, yep, I'd suggest a torn or worn seal could cause the leakage.
Measuring the spools wouldn't be so bad, if you have the specs and a tenth micrometer. Measuring the bores would require more specialized measuring equipment. Of course, the valve body itself could be defective (cracked, for example)

But again, check the easy stuff first. Might fix the problem. Also, I don't have that CD-ROM handy, I think there's a check valve in the system. That could be leaking down and would be cheaper and easier to fix.

I did 13 years all told in Naval Air. Rating was an Aviation Structural Mechanic. Part of the job was rebuilding valves and cylinders. Fortunately, that was a relatively small part of the job. Hydraulic fluid makes me itch.

 

[GONO2]

Thanks for the help!

I'll post back once I figure out what it is and how I fixed it.