Hydraulic drift on John Deere 650

[K5lwq]

BC,

Are all your leaks at the ports or is a cylinder leaking around the rod? You also said you rebuild the cylinders, what all did you replace?

If the port fittings have o-rings, you should be able to get new o-rings to seal.

 

[BCinMI650]

The front two cylinders I rebuilt with all new seals (rebuild kits from the manufacturer) except for the ports. The rear two have not been rebuilt but will be this winter, but even though they are leaking, there is no discernible drift in the action they support. Of the front two, one have a chip in the head that I believe is the cause of the leak there, but it also has a leaky port (port is leaking worse than the head). The second has the smallest leak to it, only noticeable by placing cardboard under it.

This is all awesome information everyone so thank you. It will really help prioritize work and part finding this weekend.

 

[BCinMI650]

Quick update...
It was not the hydraulic port, swapped that out and it had no effect on the drift. I've got my spare control unit in the parts washer now, so i'll swap that out and see if its a valve not returning to a closed position or something like that. Does anyone know if there is an external way to adjust that? Last step will be replacing the head and cylinder rod. Does anyone know if there is a way to isolate which side it is? I've been assuming the culprit was the leakiest side, but I guess I don't know that for sure.

Thanks

 

[K5lwq]

Ok, if you have the external leaks stopped then the next test I would do is undo the cylinder from the bucket. Then cap the extend side of the cylinder. If you have quick disconnect couplers that should work fine. Then with tractor running, try to retract the cylinder. If it does not move then the valve is the issue. If it extends while trying to retract it is the cylinder.

 

[BCinMI650]

Am I disconnecting both cylinders from the bucket to take gravity/weight of the bucket out of the equation? Or do I want the one cylinder on the bucket and one off (doing the above test on each side individually) to see if it’s something internal in the cylinder not holding the pressure?

And of course I don’t have the quick couplers, so I’ll have to pick up some caps for this weekends round of testing.

Thank you!

 

[K5lwq]

Doing one at a time is best. Yes you are testing the piston seal.

Because the surface area is greater behind the rod than in front, if seal is bypassing the rod will extend while trying to retract if that makes sense. If the seal is good and the blind side is capped, you will see no movement.

You will be blowing over the relief valve so do not do it for a long time. Just long enough to see if there is movement.

 

[BCinMI650]

Okay so I did the above test. The only time it moves is with weight the bucket still attached to 1 cylinder and lifted in the air, so basically with any weight on it at all, it drifts, with no weight it doesn’t. With the “good” side capped, the bucket just barely drifted. Even with me standing on it. With the “bad” side capped it drifted pretty quickly. I say “bad” side because it had the most internal issues and still has the heavier of the leaks. As it drifted, the capped side extended as well, even thought it was disconnected from the bucket. I think I need to replace the head and rod on it.

This was kind of opposite of what I was thinking would happen... does that make sense?

Another question. Would having the incorrect viscosity hydraulic fluid contribute to this? Previous owner informed me he threw “whatever he had on hand” in there including 5W-30 and synthetic motor oils. Could that be getting past seals easier than true hydraulic fluid?

 

[K5lwq]

I will answer your last question first. Definitely change that fluid and put in the correct fluid type recommended for your system.

This is the test and explanation of what I think you should do. Watch this video and see if it helps determine the issue.

Bypass testing a hydraulic cylinder - YouTube

 

[BCinMI650]

That video was super helpful, thank you. I was having a hard time visualizing what should be happening if incorrect. In my head i was thinking "how could retracting make the cylinder extend" and just had a mental block. It definitely extended when I retracted. pulled the "bad" cylinder and took it apart again. As I was taking it apart the rings on the piston literally fell into pieces. I'm guessing that's the issue. I'll go get new rings at lunch today, probably a couple extras for the other cylinders. I'll update when i have it all back together!

I'll also pick up correct hydraulic fluid and swap that out...

 

[K5lwq]

Sounds like you are headed in the right direction. Hopefully that will get you going.

You might consider a filter as well.