Leaking hyd. cyl, 400X Loader

   / Leaking hyd. cyl, 400X Loader #1  

Red Horse

Veteran Member
Joined
Dec 12, 2010
Messages
1,174
Location
Bolton, MA
Tractor
Deere 655ZTrak, Deere 4720 Cab, 400 X LT 155
Well the 400X loader on my 4720 appears to have some packing issues on the loader boom cylinders. In a little over two hours, the arms dropped 8". Three days later, from a height of 48" the bucket is now on the concrete floor..

Any clue as to what typical cost is to replace packings? Not only does boom drop, but I tried to load a structure I was told weighed about 1200 pds on the back of a one ton and couldn't get load any higher than about 18". I think a 400X is rated for over 2000 lb.
 
   / Leaking hyd. cyl, 400X Loader #2  
I believe I have the answer for you as far as cost. I'll have to go find the receipt in my garage though later. I swear it was around 500 bucks. My 300cx dump cylinders were doing the same thing from day 1 and they repacked both cylinders. The cost was on the receipt however, it was under warranty. The problem still happened though about a week later and it turned out I got a bad batch of cylinders. They were defective inside so john deere had them replace both cylinders after that
 
   / Leaking hyd. cyl, 400X Loader
  • Thread Starter
#3  
I believe I have the answer for you as far as cost. I'll have to go find the receipt in my garage though later. I swear it was around 500 bucks. My 300cx dump cylinders were doing the same thing from day 1 and they repacked both cylinders. The cost was on the receipt however, it was under warranty. The problem still happened though about a week later and it turned out I got a bad batch of cylinders. They were defective inside so john deere had them replace both cylinders after that
THX Big M. I had heard it was pricey. I have worked on older machines with the typical packing nut on the ends and it was not rocket science but these "sealed" units are something else.
 
   / Leaking hyd. cyl, 400X Loader #4  
Redhorse
Have you looked at the breakdown of the parts shown in jdparts ? Doesn't look to be real difficult to remove the snap ring and pull the cylinders apart to get at the seals.
 
   / Leaking hyd. cyl, 400X Loader #5  
Well the 400X loader on my 4720 appears to have some packing issues on the loader
boom cylinders. In a little over two hours, the arms dropped 8". Three days later, from a height of 48" the bucket
is now on the concrete floor..

That's about normal for JD FEL valves with some hours on them.

On one of my 4300s, one FEL boom cylinder piston seal was completely blown out and the loader would still leak
down at about that speed...3 or 4 days to go from chest height to ground.

The other symptom you report (can't lift heavy loads) does indicate a bad boom piston seal or 2. I do
NOT buy from JD any more, however ($!). Measure the sizes and try Herculesus.com.

BTW, with a blown seal, my FEL could only lift its own weight (empty) about 4 or 5 feet high.
 
   / Leaking hyd. cyl, 400X Loader
  • Thread Starter
#6  
Guys- Thx for input- I will check out the schematic. Should not be rocket science.
 
   / Leaking hyd. cyl, 400X Loader #7  
Here is a pic of the parts..
 

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   / Leaking hyd. cyl, 400X Loader
  • Thread Starter
#8  
Here is a pic of the parts..
Thx- just downloaded and printed off web site. 49 bucks and change per cylinder-so 100bucks and a lot of cussing on my part and I should be done......Stay tuned!
 
   / Leaking hyd. cyl, 400X Loader #9  
don't expect internal seals to fix a settling boom. The reason is that the extended cylinders can't retract even with NO seals (Unless fluid is going back through the valve, or oil is leaking externally). When a cylinder retracts, the rod has to displace oil. If there is no where for the oil to go, the rod can't retract. It's that simple.
Now, the lift capacity being reduced...that's a different story. That sounds like an internal seal. You will still have the settling issue when you are done.
In Big Mikes case, he had a problem with the internal seals of the DUMP cylinders. They EXTEND when they settle, so the rod exiting the cylinder increases the volume, and pulls air in from the external seals to take up the extra space. The external seals do a poor job of sealing a vacuum.
 
   / Leaking hyd. cyl, 400X Loader
  • Thread Starter
#10  
don't expect internal seals to fix a settling boom. The reason is that the extended cylinders can't retract even with NO seals (Unless fluid is going back through the valve, or oil is leaking externally). When a cylinder retracts, the rod has to displace oil. If there is no where for the oil to go, the rod can't retract. It's that simple.
Now, the lift capacity being reduced...that's a different story. That sounds like an internal seal. You will still have the settling issue when you are done.
In Big Mikes case, he had a problem with the internal seals of the DUMP cylinders. They EXTEND when they settle, so the rod exiting the cylinder increases the volume, and pulls air in from the external seals to take up the extra space. The external seals do a poor job of sealing a vacuum.
I'm confused. It is a double acting cylinder-not a single action. Thus if boom is raised , force is on the "down" side of the boom. If seals are bad, doesn't "x" volume of fluid simply take path of least resistance and push to other side of piston??? Same volume of oil is in the cylinder bore-it just is now on the other side. What am I missing??
 
 
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