excavator crowd cylinder

jacks

Member
I need to reseal the 'crowd' cylinder on a Deere 690B excavator. This is the cylinder that is mounted to the top of the boom and moves the stick. According to the shop manual, it says to retract the crowd cylinder (which will stretch the stick out straight), lower the bucket, and then remove the entire cylinder. Is this the best way, or could the rod be pulled out of the barrel and the new seals installed. Any advice is appreciated.
 
I always removed them from the machine. We had a cylinder bench to lay them in and a hydraulic wrench or torque multiplier to remove the piston from the rod. Some of the rod nuts or bolts had thousands of pounds of torque on them. If just the o ring between the head and barrel were leaking I have replaced the o ring by cutting them and gluing it back together with a Loctite O ring splicing kit. Its nice to have some hoses made up to cycle the cylinder once removed and run the oil out of the cylinder into a bucket.
 
I had the crowd cylinder repacked on my 690 a couple years ago for about $300. I removed the entire cylinder and took it to a local hydraulic shop. With all of the weight involved, I don't think you could easily remove just the rod and then be able to get the piston back in without risk of damaging the new seals. I know the shop had a hard time getting the cylinder cap off, and the spec for the piston nut is close to 1000 ft-lbs so no way I could have gotten that off either. For a small cylinder it is worth a try but that one is much too big to do in place.
 
I resealed the crowd and lift cylinders on my Ford 655A backhoe this past spring on the machine. I had help. Never could have done it alone. And then one of us was standing on a pallet on a forklift.
You've got something there- twice as big? I think just getting the cylinder off will be enough fun!
 
Having done quite a few of them, a direct answer to your question is that YES, the rod can be pulled out, new seals installed, and then put back in without pulling the barrel off.

That said, the main thing is to have something on hand to pick up the rod and get it lined up before putting it back inside the barrel. This is something that you will have to do regardless of whether the cylinder is on the machine or not, so that's not a big issue. The benefit is that the barrel is pinned in place, and held stationary so it often makes things a lot easier, especially if you can stand on the ground, or a platform, and get to the rod end easily enough. Personally I use the crane on my service truck as it allows me to do the job by myself, but if your using another machine it would help to have an operator so one can run the machine, and the other can put the rod back in.

Now others have made the comment about the rod nut, that holds the piston on being tight. That's true, and 1000 ftlbs is actually low for some. Many of the ones I've pulled have been between 3000 and 4000 ftlbs. Thankfully I've got a home made, mobile, cylinder bench that I can take with me in the field to do that part, instead of trying to rig up something to get the nut off. As far as the head, where the rod exits the cylinder, once again having the barrel attached to the machine makes getting it off much easier as you don't have to rig up a way to hold it still while you get it broke loose. As many different ways as they are attached I'm not even going to get into actually getting it broke loose. Still having the whole assembly attached to the machine, and stabile, in 99.9% of the situations I've encountered, means more than anything else to the ease of getting it apart.

Beyond that, when you get the machine setup to pull the rod, you need to loosen the lines going to each end of the cylinder so it doesn't draw a vacuum as you try to pull the rod out. Once you get the pin out of the rod, raise the cylinder up and let it set on a block at an angle that allows the rod to clear any obstructions as it comes out. Take everything apart, install the new seals, and then carefully reassemble it. On that note, one of the reasons you need to be lined up, and relatively stable, is that you might have to assist the rod reentering the barrel with a hammer as the seals can often be a tight fit. I've had to do this many times, and can't remember cutting a seal going back in but once, and I chalk that one up to the simple fact that crap happens. Good luck.
 
I really appreciate the advice. We recently revealed the boom cylinders and removed the pins at the top of the cylinder, lowered the cylinders to horizontal and removed the rods. To reinsert the rods, we found that even a sledge hammer driving on the back end of the rod was not enough to get the seals compressed and started into the barrel. Ended up using a porta power pushing against a loader bucket to get the ram reinstalled. Since we were standing on the ground it was not too bad. With the crowd cylinder being about 10-12 feet off the ground, I am concerned about getting a safe platform to work off to get the rod reinstalled. I do have a 175C loader which I think will be able to reach high enough to lift the whole cylinder assembly off and back on. I think I will err on the side of safety and remove the cylinder as a unit. Thanks again for the good advice, each had some good points.
 
Tuck it down into transport position and unhook the end that attaches to the stick will be closer to the ground and easier to work on. Piston nut will be the challenge. Use a piston ring compressor and lots of oil to install rod back in barrel.
 
Bill, I thought about doing it that way. It looks like the boom would have to be supported if I disconnect the crowd cylinder with the stick in transport position. I appreciate the advice. Doing it as you describe, have you had to support the boom weight with the stick unlinked?
 

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