JD 420 Loader bucket cylinder drops

[jorswift]

Hey all,

Going to change out the Hydraulic and Transmission fluid shortly and figure I would maybe try and rebuild the bucket cylinders. The bucket tends to drop as soon as it has a load it in, or not, but faster with load. It is the bucket's curl that drops, not the lift. However, I dont ever see any fluid or puddling from the cylinders. Would this require a rebuild or something else? Thanks.

 

[LD1]

With curl cylinders it can either be the valve or the cylinders.

Lots of un-necessary cylinder rebuilds happen because people don't troubleshoot the problem.

If the cylinders are extending....it's one of two things happening.
1. Oil from the rod side is returning back through your control valve.
2. Cylinder seals are shot and oil is bypassing the piston.

Fortunately for you, you asked the question before wasting money.

To troubleshoot you need to isolate the valve from the cylinders.

Does your loader have quick couplers? I'd so because that makes it easy...since they are essentially plugs when disconnected.

Get a load in the bucket (to exaggerate the symptoms). Set the bucket on something or even flat on the ground and shut the tractor off and bleed the curl circuit my moving the joystick with tractor off.

Unhook both curl hoses. Again, easy with quick disconnects. If no disconnects....manually remove the hoses from the loader valve or even at the cylinders and plug the cylinder side of the hoses(not the valve side).

Now restart the tractor, raise the loader (don't touch the curl function because it is now unhooked) and monitor what the bucket does.

If it holds it's position.....you have an issue with the valve on the tractor.

If the bucket still dumps on its own at about the same rate....one or both of the cylinders need rebuilt.

There is further testing to isolate of it's one or both cylinders....but that is a little more involved. And on a loader that size....IF it's the cylinders I'd rebuild them as a pair anyway

 

[jorswift]

With curl cylinders it can either be the valve or the cylinders.

Lots op in necessary cylinder rebuilds happen because people don't troubleshoot the problem.

If the cylinders are extending....it's one of two things happening.
1. Oil from the rod side is returning back through your control valve.
2. Cylinder seals are shot and oil is bypassing the piston.

Fortunately for you, you asked the question before wasting money.

To troubleshoot you need to isolate the valve from the cylinders.

Does your loader have quick couplers? I'd so because that makes it easy...since they are essentially plugs when disconnected.

Get a load in the bucket (to exaggerate the symptoms). Set the bucket on something or even flat on the ground and shut the tractor off and bleed the curl circuit my moving the joystick with tractor off.

Unhook both curl hoses. Again, easy with quick disconnects. If no disconnects....manually remove the hoses from the loader valve or even at the cylinders and plug the cylinder side of the hoses(not the valve side).

Now restart the tractor, raise the loader (don't touch the curl function because it is now unhooked) and monitor what the bucket does.

If it holds it's position.....you have an issue with the valve on the tractor.

If the bucket still dumps on its own at about the same rate....one or both of the cylinders need rebuilt.

There is further testing to isolate of it's one or both cylinders....but that is a little more involved. And on a loader that size....IF it's the cylinders I'd rebuild them as a pair anyway

Thank you. I will most def try this out and see what happens!

 

[npalen]

What LD1 says above and also, if the open hoses leak fluid excessively, the curl valve spool and/or it's housing bore may be worn excessively and possibly in addition to bad seals in the cylinders. The hose leakage would probably be noticed when the loader arms are being raised building pressure in the system.

 

[LD1]

Thank you. I will most def try this out and see what happens!

Pleas do and report back and keep us posted

 

[jorswift]

Pleas do and report back and keep us posted

I tried the test today. Unfortunately, its still so wet out and I dont have anything close to load. But I drove the tractor up and down the drive with the forks on it, as it seems to be heavier than the bucket. It didnt seem to move much. But once I started hitting the bumps it started to let out? I am going to try again when the weather breaks a bit more this week or when more time allows.