# Leaking hydraulics



## JimK (Jul 19, 2004)

Let me first summarize: I bought a 1990 JD 955 with 70A loader and #7 BH back on July 23. Within 10 minutes of trying out the BH, a hose blew. It needed that repaired and more, so off to the JD dealer it went. Two weeks later, I have a much happier tractor, and it has a happier owner.

So, last weekend I used it quite a bit to move concrete debris from a large slab I broke up with a 90lb jackhammer (oof!). Since I got it back from the dealer, each successive work session has revealed more leaking cyclinders in the attachments. By leaking, I mean oil drips past the piston rod seals. I also find that my backhoe and bucket drift down fairly rapidly. I have to pull the boom back on the BH every 5 minutes or so when I am moving material with the front bucket. When I have the front bucket down supporting the front of the tractor while I am using the BH, after about 10 minutes it no longer is supporting the weight of the tractor. The stabilizers for the BH also leak down after about 5 minutes. I notice this when the tractor starts to "dance" on the rear turf tires as I am digging. Even the swing cylinders are now starting to weep, and don't feel as strong as the rest of the BH. Overall Iam very pleased with the strength and performance of the BH and FEL. I just wish the FEL bucket tilted back farther.

Given the age and hours (~1425), I suspect the cyclinders all need service. My dealer said that there is a "re-pack" kit for the cylinders that goes for about $25 each. Is that all that is needed? What is in the kit? I have no problem rebulding them myself if all they need is new seals.

Thanks for any guidance or referrals to on-line hydraulic cylinder service info.


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## Live Oak (Dec 22, 2003)

Great to hear about the improvements to your machine so far Jim. Yes you can get repack kits for your cylinders but you need to inspect the cylinder piston rod chrome plating and outside diameter to see if they are still within spec. (i.e. any chrome plating peeled or peeling off, are the rods straight - no bends, the inside of the cylinder you will have to inspect when you tear it apart but check for the same things more or less) If the cylinder is servicable the repack kit should make a big improvement in leak down and seepage. 

Some other things you may consider if you haven't already is that you will need BIG spanner wrench to break torque and remove the cylinder plug and some pretty good sizw wrenchs to remove the nylock nut from the cylinder piston rod guide/plug.

Getting the repacked piston back into the cylinder is a bit of a tight fit but it needs to be and just be gentle and careful about gently tapping it in without damaging it. Be careful and gentle about threading the plug/guide back into the cylinder. If the threads are not to badly damaged; you can usually clean them up with a proper pitch thread file. I a little bit of grease or oil on the threads is a good idea too. 

Remember to buy more Hygard, figure on average somewhere around a gallon per cylinder. I recommend the standard Hygard as the Low Viscosity Hygard will leak that much easier. 

On a safety note be ABSOLUTELY certain that each cylinder has been FULLY relaxed that and the boom, outrigger, bucket or whatevery CANNOT move when you break torque on the hydraulic line. This will #1 save you from taking a nice oily shower.   MOST IMPORTANTLY be ABSOLUTELY certain your hands, feet, or any other parts or your body are well CLEAR of any potential movement of the tractor's appendages since they can leak down really fast and possibley crush, pinch or amputate a limb or worse. Just be very award and careful.

If the cylinders still leak down without improvement and the cylinders looked in good shape as well as within spec. Take a look at the SCV control valve block and valves. I have had to repack these as well and they are a lot more involved. This is where that John Deere shop manual or CD will come in real handy. Good luck and let us know how the job went! :thumbsup:


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## JimK (Jul 19, 2004)

Thanks Chief. Prompt with the valuable input, as always. :thumbsup: 

My dealer said since my cylinders were the "older" style, they had circlips at the cylinder ends, and would be easy to disassemble. If not, I have a good selection of tools, and will buy what I need to do the job, if necessary. All the chrome on all the rods looks pristine, but of course the bores may not be as good, so I will have to investigate that when the time comes.

Since the 955 is a hydro, will the standard Hygard be OK instead of the low vis? The manual and the dip stick say to use low-vis. I do need to get my tech manual and CD.

I hear you on the "stored energy" safety point. I will certainly relieve all the cyls before I open any up. I will have everything "grounded" or blocked too to keep the mechanical movement to a minimum. I am half tempted to remove each attachment in the garage and work on it off the machine. That way I can clean it up and maybe even re-paint.

Hoo boy. Sounds lke I am already restoring this machine . . .


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## Live Oak (Dec 22, 2003)

Unless you leave the tractor parked outside during the winter and or use it outside during extreme cold; I would stick with the standard vis,. Hygard. That is what I use in my 4410. I went with what the owner's manual called for on the temperature chart. 

You should also verify the outside diameter of the piston rods are within spec. with a micrometer as well. Just to be on the side of certainty.


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