Boom Cylinder Dripping - Need Advise.

[Tractor Pilot]

I have a 1997 John Deere model 70 loader on my JD770 tractor. One of the boom cylinders (right side) drips hydraulic fluid where the rod enters the cylinder. As far as I can tell, it doesn't drip or leak when I am using the loader (the rod is dry). After I shut the tractor off it drips about 3-12 drops over a day or two then stops. Sometimes it doesn't drip at all. The cylinder has done this since I bought the tractor about 6 months ago.

I suspect that when the cylinder is pressurized that the seals are sealing fine but after the pressure is removed when I turn off the tractor that a seal may relax just enough to cause some minor dripping. Is this serious enough a leak where I should buy the seal kit and replace the seals in the boom cylinder or should I wait till the leak gets worse? The other boom cylinder (left side) doesn't leak. The loader seems to work fine as is.

Any advise would be appreciated.


Bruce

 

[kennyd]

To fix or not to fix...it's really your call. You are probably correct about why it does not leak under pressure, so if it was me-I might get the kits to have on hand and rebuild them at my leisure-maybe over the winter or another time when you don't need the loader for a while. You should do both cylinders at the same time also.

 

[Tractor Pilot]

kennyd,

Thank you for the advise. I think I will get the kits and wait until the dripping gets worse on the one cylinder before I replace the seals on both boom cylinders (my local John Deere dealer wants $47.03 per kit plus tax; greenpartstore.com wants 42.75 plus shipping). I park the tractor in the barn that has a dirt/gravel floor so I don't mind a few drips. The cylinders are 14 years old. I'm surprised that only one cylinder on the loader occassionally drips. I already replaced the o-ring on the fuel shutoff valve that was dripping. All seals wear out over time.

I was looking at the dripping boom cylinder a bit closer today. The open end of the snap ring was on the bottom of the cylinder. I rotated it so that the open end was on the top of the cylinder (the other 3 cylinders had the open end of the snap ring on the top). I exercised the loader, lowered the bucket, and shut off the tractor. I went back several hours later and no drips. Whether that fixed it or this is just one of those random times that it doesn't drip remains to be seen.

Bruce

 

[wdchyd]

Bruce,

another thing to do while you get seal kits and wait for good time to repack them.......oil up the other cyl gland (if you're planning on repacking both).....if you dump oil on the gland a few times it may help you when the time comes the do them.....

occasionally the "Dry" one can be more difficult to take apart......just a heads up....Good Luck......:thumbsup:

 

[Tractor Pilot]

I decided to rebuild the boom cylinders on my model 70 loader, but I have a few questions before I get started:

1. Only one of my boom cylinders is leaking (right side). The left side is fine. What is the reasoning that it is recommended to rebuild both cylinders at the same time? I plan on rebuilding both - just curious of the reason.

2. On the schematic I originally posted for the boom cylinder, how does the gland assemply (#4) come out? There is a snap ring. Will it come out with a good tug on the cylinder rod after the snap ring is removed or does it also screw out?

Thanks for any help. I plan on taking and posting pictures of the rebuild process.

Bruce

 

[kennyd]

1. Only one of my boom cylinders is leaking (right side). The left side is fine. What is the reasoning that it is recommended to rebuild both cylinders at the same time? I plan on rebuilding both - just curious of the reason.

They both have the same wear&tear on them-and both have been in there same amount of time. And if your luck is like mine the other would start leaking a week after the first one was fixed. If it wasn't for bad luck sometimes, I'd have none at all
Same thing goes for tires, brakes, shocks, headlights, windshield wipers, shoes, socks, gloves....they should always be replaced in "pairs".

2. On the schematic I originally posted for the boom cylinder, how does the gland assemply (#4) come out? There is a snap ring. Will it come out with a good tug on the cylinder rod after the snap ring is removed or does it also screw out?

Yes, after the snap ring is pulled, the rod should come out.

 

[Tractor Pilot]

kennyd,

So in addition to the snap ring, the gland assembly doesn't screw in to the cylinder? So the only thing between 2100-2500psi and the atmosphere is a little snap ring? If true, WOW!

When you have rebuilt loader cylinders, do you quick disconnect the entire loader off the tractor and then pull the cylinder or do you leave it attached to the tractor and pull off the cylinder?

Thanks,
Bruce

 

[kennyd]

I left my loader on the tractor and completely removed the cylinders. Just be careful the it does not move.

There are lots of different way's to close cylinders, from retaining wires, threads, internal locking rings, internal snap rings, external snap rings...

Notice that they include a new snap ring in the seal kit also.

 

[Wayne County Hose]

Disconnect the hoses and use the rod as a slide hammer to remove the gland.

 

[Tractor Pilot]

So today I replaced the seals in the right boom cylinder that was dripping and now have the cylinder mounted back on the tractor. Before I start the tractor and check for leaks I wanted to ask if I need to do any special procedure to bleed the air from the right cylinder. I haven't replaced the seals in the left boom cylinder yet (it wasn't leaking) but I plan to next week.

So as the tractor sits now, the left boom cylinder is full of fluid and the right boom cylinder is full of air. Do I just operated the boom hydraulics slowly and in small increments and as the fluid fills the chambers on both sides of the piston in the right boom cylinder the air will eventually self-bleed out into the hydraulic sump?

Does anyone have a better suggestion/method? I'll post some pictures and give a brief write-up about this project after I finish.