When I purchased my land, one of the main selling points was an old excavator left on my land. An old Drott 40 Cruz-air, basically a track hoe on tires.  It had been sitting for years and belongs to the neighbor.   I've recently had some earthworks done at my place for a building pad, and at a good buddy deal of 125 dollars an hour to rent a machine and operator, hundreds of dollars can add up quickly directing earth moving equipment to implement our permaculture designs.  The amount of work a good operator can do in one hour is incredible. However, having my own machine to play with, even if it takes 5 times as long to perform that same amount of work, would be not only a great deal of fun but also very rewarding knowing you were able to carve out your own designs in the landscape.

Heres a picture of the machine we are trying to revive.

It was parked in the woods and left when a hydraulic line to the tilt/twist bucket ruptured and was not wanted to be repaired.  I replaced that hydraulic line and we were able to drive it out of the woods to this place, where it sits now.  Between repairing the hydraulic line, running new fuel lines and running new battery cables, I have about 400 dollars in the machine.  If i can spend 1000 dollars and having a working turn key excavator, it will be entirely worth it. So here we come to a dilema. One of the hydraulic cylinders is leaking, and its a big one up high.  The machine cannot run for very long because the cylinder leaks so badly.

Heres an image of a exploded view of a hydraulic cylinder.

The reason it leaks so badly is a failed seal in the gland that seals the cylinder rod.  The way a hydraulic cylinder like this works is that pressure is constantly allowed to both sides of the piston.  This lets the machine be able to hold positions without falling. The cylinder we are servicing controls the curl of the bucket.  When you require the cylinder to move one direction or the other, pressure is vented off from the opposite side via the controls in the machine, and the side of the piston with the greater pressure allows the cylinder rod to move towards the lower pressure.  When you release the controls it closes off the "pressure dump" and the pressure on both sides of the piston is again equal. Causing the cylinder rod to be "locked" in that postion.  So with a bad seal in the rod gland, even though we are not operating the curl of the bucket, it still leaks anytime the machine is running and must be repaired.

This is the cylinder we need to repair.

There are several designs of glands, ours is a very common one using pin holes like a spanner wrench.  Someone in the past tried to take this apart using a punch and a hammer.  This will not work and only damages the gland. You need the correct tool.  

Here is the face of the gland nut

And here is the tool used to loosen the gland nut, called a gland nut wrench.  I purchased this tool on amazon for around 85 dollars.

What your going to need to perform this job is a whole arsenal of tools, hammers, pry bars, giant wrenches scraps of wood etc.

You need to fire up the machine and get it to a good resting postion for the cylinder you are going to service.  Since ours controls the curl of the bucket, I extended the boom out as straight as a could to make it closer to the ground, and curled the bucket and let it rest flat on the bottom.  I shut the machine off and with no more pressure I allowed the natural weight of the boom to rest the bucket on the ground.  If you using the downward pressure of the hydraulics, you can lift the machine and cause the pins to become jammed and you will never get it apart.

Nows the time to break the gland nut loose. I parked the truck underneath the boom to give me enough heighth to work on the machine.  Look for any set screws or roll pins that could be used to lock the gland in place to keep it from unscrewing.  Ours had none, but looks like a roll pin could have been present at one time. Using your gland tool, a breaker bar and a cheater pipe break the gland nut loose.  The tool is 3/4 drive, I used a 3/4 to 1/2 adapter, a half inch breaker bar and a 8 foot piece of pipe.  This is a critical step.  If you cannot break the gland nut loose, your done, thanks for playing.  Ours broke loose.

After the gland nut is broke loose.  Were ready, this is going to happen.  You do not need to pull the whole cylinder off.  We only need to pull the cylinder rod, gland nut, and piston out of the barrel. If you've positioned the machine correctly, The cylinder pin will not be in a bind.  Usually there is a bolt or pin through the end of the pin to keep it from working out that will have to be removed.  It locks the pin in the machine much like a cotter key.  Ours was missing and will have to be replaced during assembly. Give the pin a few whacks with a hammer and see if it will move.  Wear your safety glasses. Chipping paint can hurt you badly.  Notice have weve hit the end of the cylinder rod pin in and its much closer to flush then all the other pins on the machine.  Ours is loose and not in a bind.  Were in the correct position to take this apart.

The tools I used were just a seal driving rod and a mini sledge.

Ok now here comes the safety.  You need to analyze the machine carefully and consider exactly what your trying to do.   This machine is 39,000 pounds.  Its heavy.  All the pieces of it are heavy.  If something, shifts or goes wrong, your going to be badly injured or possibly killed.   There are so many pivot and pinch points. You need to use wooden cribbing to brace this machine for three important reasons. One to provide a safe working environment, two the pieces of the hydraulic cylinder are precision machined and contact with hard surfaces like metal can easily damage it. And three, the machine must not move so that it can be reassembled easily. If you pull the cylinder out and the boom shifts, how in the world will you ever get everything lined back up?.

It never hurts to add more cribbing then you will ever imagine needing.

Wooden I beams screwed together

Cribbing, Cribbing and more cribbing shots, very important!

Now that you have the machine braced securely. You need to loosen the hydraulic lines running to the hydraulic cylinder.  This will relieve any pressure still in the system, and allowed the piston to be pulled out because a vacuum cannot be created on the back side.  I threw my tool bag on the boom and crawled down it to reach the spot I needed.

You see that hole in the center of the boom?  I got extremely lucky. I got down the boom fine and loosened my lines, but when I tried to come back up, that hole was full of hornets! I was literally stuck on top for awhile before I got brave enough to just shimmy down and jump on the truck.

The line was cresent wrench sized, the biggest wrench I brought was 34 mm and it was still too small.  The lines don't need to come off, just loose.

At this point you need to crib the barrel end to support it, and I made another just to support the rod.

With the barrel supported, you can go ahead and remove the rod pin.  Be careful of components that will fall off once the pin is not in them such as this.

As your drive the pin out, it may bind, the swing arm on the other side was bieng forced out and it had to be driven towards the boom occasionally to promote smooth pin travel.

Pin removed

Now your to the point of needing assitance.  Go ahead and unscrew the gland the rest of the way and pull it off.  Be prepared to catch any escaping oil.  Pry the cylinder up and slide your cribbing back with the help of an assistant so that the rod and gland will clear the boom and come over the top easily.

You cannot have enough wood and cribbing!  The cylinder, gland and piston must be protected from damage!!!  Now were ready to pull the assembly out.  

We used a chain to wrap through the pin hole and used the tractor to pull the piston from its bore. You could have used something like a come along.

We pulled the piston and an absolute insane amount of oil came out and completely covered the truck and filled the bed. Im not sure how you could possibly catch this.  However disappointing this was, it was actually good it happened this way.  The car washes are set up with oil and grease traps to catch oil and are capable of handling this. So filling the truck kept the fluid off the ground and at the car wash who can handle it properly, but it made a heck of a mess.

With the cylinder out, two people could pick it up and slide it down the boom and off into the truck.

Thats it for part one.  Next I'll take the piston into the shop and show you how to rebuild it, and then reinstall.