# Repairing a Hydraulic Cylinder Leak



## 32-0-0

One of the hydraulic cylinders that raises the boom on our JD 640 front-end loader is dripping hydraulic fluid. This drip is coming out where the piston exits the sleeve.

I've never broken a cylinder apart - I've just taken them
to a shop to have the repair done. But I'm getting tired of spending a few hundred bucks to have this done.

Is this a difficult repair? Are there any special tools
needed?

Thanks,
Chris


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## CowboyRam

I would look at the shaft to make sure it is not pitted to much. If it is in good shape you probably just need seals; I am not sure how hard it is to take it apart, but don't think it would be difficult. It gets expensive if you have to replace the shaft. We had two completely, and had to have the shaft replaced. I cost us around $2200 for the two.


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## r82230

Can you just tighten the packing seal? That's an option on some cylinders.

As far as changing yourself, I've done some that didn't need any special tools. You just need to place all the packings in the proper order (Vaseline even can help on reassembly). Where I get my packing parts from, they are very good at putting the pieces in proper order needed to re-assemble, hope your supplier does the same.

Last tip, if rod is pitted (rusty pits even), a possible fix is to remove rusty pit spot only, clean well, then 'borrow' your better half's finger nail polish. After applying polish to cleaned pits (allowing it to dry), gently sand down the polish to make rod smooth again. Don't have a clue to how long your 'farmerized' repair will last, but...&#8230;&#8230;&#8230;&#8230;&#8230;&#8230; cheaper than new rods, I think. 

HTH

Larry


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## Farmerbrown2

Repairing cylinders is not difficult. I like to take pictures with my phone as I take them apart so I put them back together correctly.

I have scufffed many bucket cylinders on backhoes and excavators. Biggest thing is get them polished out quickly before the seals get damaged don't be afraid to use emery cloth on them. The other option is way to expensive as CowboyRam stated.


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## HAYcorey

Get yourself a gland wrench (I bought an OTC brand for about $20) and locate a good hydraulic supply house that's near you and you'll save lots of money.

Leave the cylinder on the machine to hold it while you loosen it. Once you get the gland off remove the rod end of the cylinder from the machine. Then pull the rod out of the tube. You'll see a big nut that holds the piston in place. These usually have fine threads and were installed using loctite. Use a MAPP gas or propane torch to heat the nut. Doesn't take a lot of heat < 500 degrees if I recall and the nut will come off real easy with a big socket and pull handle or a good impact wrench. You'll need to hold the end in a good vice or just pin it back to the machine to hold it.

Hydraulic Supply Company is really good in our area and the guys there normally remove and replace all the seals and o rings one at a time as they measure and pull the new ones off the shelf. The first cylinder I repacked was off a bobcat mini x and the kit from the dealer was over $80. The same seals for the second cylinder on the same machine at hydraulic supply cost less than $15.


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## Gearclash

One thing to watch for is wear of the bore that the cylinder rod slides through, sometimes known as the cylinder head. If the bore is significantly worn, replace the head as it will be hard to keep seals in it otherwise.


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