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1999 LULL 644D-34 Highlander

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CarpenterRick

Member
Joined
Jul 1, 2011
Messages
15
Location
Louisiana
Has anyone replaced the boom extend cylinder seals on one of these machines? I received an estimate that stated I must replace the counter balance valves as well. I know my valves are fine. The shop manager said they may not be able to reinsert the piston without removing one of the valves, and once they are removed they must be replaced with new ones ( I am sure this is for liability reasons as another memeber had stated).

I am ready to handle this project myself and need a couple of tips from someone experienced with LULL.

Any guidance is very much appreciated.

Thank you,

Rick
 
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BillG

Senior Member
Joined
Mar 26, 2009
Messages
510
Location
S. Wisconsin
I just did one a few months ago. Simply reinstalled the ram until the piston passed the retract port and retracted it via the hydraulics after the head was reinstalled. No problems, just go slow installing it so the air can escape. It doesn't have to go in very far. Also remove the two mounting bolts at the back to allow for rod clearance if you are not going to remove it from the machine.
 
joestewart

joestewart

Well-Known Member
Joined
Oct 14, 2009
Messages
204
Location
Lafayette, LA
Check the service manuals that are available online on the JLG site for the 644C and 644E and see if your boom extend cylinder is the same. Follow the procedure given in those manuals if it is:

http://csapps.jlg.com/OnlineManuals/browse.aspx?path=Lull/Lull Telehandlers&title=PDF Manuals&refkey=http%3a%2f%2fwww.jlg.com%2fen-US%2fMaintenance.Repairs.html&link=

I have a pdf of the service manual for the older Lulls and can email it to you if you want it, but I'm pretty sure that the cylinders and counterbalance valves are different. I am not familiar with the 644D
 
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CarpenterRick

Member
Joined
Jul 1, 2011
Messages
15
Location
Louisiana
Bill,

I have couple of questions:
1. Did you remove the counterbalances valves at all (I am sure I can get the piston out with the hydraulics)?
2. It appears that once I remove the main pin, I can chock the cylinder up to allow for rod access/ clearance (asking this as I did not understand the comment about the two bolts at the back). Unless you are referring to the two 1-1/4" bolts mounting the rear of the cylinder to the machine.
3. On my original estimate from the repair shop, there was mention of "steam cleaning". Any idea on what they are referring to?
4. This will be my first ever cylinder repair, any basic tips on dealing with pressure/ bleeding air etc. I assume that the hydraulics can do much of the work for me (as you mentioned in your previous post).

I'll post some pics soon. As long as the seal kit is in stock, I will perform the repair this weekend.

Thank you very much, Bill.
 
B

BillG

Senior Member
Joined
Mar 26, 2009
Messages
510
Location
S. Wisconsin
CarpenterRick said:
Bill,

I have couple of questions:
1. Did you remove the counterbalances valves at all (I am sure I can get the piston out with the hydraulics)?
2. It appears that once I remove the main pin, I can chock the cylinder up to allow for rod access/ clearance (asking this as I did not understand the comment about the two bolts at the back). Unless you are referring to the two 1-1/4" bolts mounting the rear of the cylinder to the machine.
3. On my original estimate from the repair shop, there was mention of "steam cleaning". Any idea on what they are referring to?
4. This will be my first ever cylinder repair, any basic tips on dealing with pressure/ bleeding air etc. I assume that the hydraulics can do much of the work for me (as you mentioned in your previous post.
Click to expand...

1. No, I just removed the head (loose) and used the hydraulics to push the ram out.

2. I am referring to the two large ones in the back end of the cylinder. If you don't remove them there is not enough wiggle room (technical term) to block up the head end.

3. They were just referring to cleanliness and making sure there is no water in the cylinder when reassembled.

4. Just use a little common sense and make sure that you get the seals installed in the proper orientation. Laying them out and understanding that the pressure goes against the mouth of the seal and that the wiper (farthest outside seal) can be damaged, and any garbage (another tech term) that gets by it will ruin the new seals. Also lube up everything with a good quality assembly grease will make everything go better. Inspect the chamfer on the inside of the tube, this is the place where more new seals are destroyed. Check for rough spots and imperfections here and also on the entire length of the rod and tube.

Also use web straps, not chains when you handle the rod. The rod is heavy so position the lift somewhere that will allow for overhead support. You will need a large wrench to remove the piston, 1 inch drive will probably be needed as the torque needed to tighten it is considerable. Just take notice of the amount of pull needed to loosen it. Placing the rod end back in the socket (where you removed the pin) will give the needed holding.
 
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B

BillG

Senior Member
Joined
Mar 26, 2009
Messages
510
Location
S. Wisconsin
Sorry, i misread your question on steam cleaning. The reason for the caution is to prevent pressure build up inside the cylinder when it is sealed. With the valves in place it would be a potential safety hazard.
 
joestewart

joestewart

Well-Known Member
Joined
Oct 14, 2009
Messages
204
Location
Lafayette, LA
This advice comes from a novice. The only hydraulic cylinders I've rebuilt are the ones on my Lull:

1. The "high pressure sealing ring" on the piston (it was yellow in color on all my cylinders) will stretch a little bit when you install it onto the piston. This stretching makes it difficult to re-insert the piston into the bore of the cylinder and also increases the chance that you will damage the ring when you push it in. The guys at the hydraulic shop recommended that I put a ring compressor on it (or a hose clamp with cardboard used for padding) for about 10 minutes immediately before I attempted to re-insert the piston into the bore of the cylinder - helped a lot!

2. I used petroleum jelly for lubricant during assembly.

3. I used a 1 inch drive impact wrench to get that nut off the piston and to re-install it. I understand that the torque on that nut exceeds 1000 foot-pounds!.

4. If there is residual pressure beneath the counterbalance valves after you loosen up the bolts holding it down, I understand that there is the possibility that the valve can be propelled off of the cylinder with such force that it becomes a dangerous projectile that can cause injury or death. There's a warning about this in the manual. Mine came off ok, but I did get partially soaked with hydraulic fluid when I took one of them off. They recommend that you wear eye protection during this part of the disassembly.

5. I had to use a gigantic (60 inch) pipe wrench to loosen the end caps. The wrench slipped and put a nick in the chrome rod. Like Bill said, keep chains and heavy tools away from the chrome rod.

It was a royal hassle to do the labor myself, but I learned alot and saved about $3000!
 
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CarpenterRick

Member
Joined
Jul 1, 2011
Messages
15
Location
Louisiana
Bill and Joe,
Project complete! I pressure washed the machine for a clean work environment (10 AM yesterday) and began the repair at 12PM. I was 100% complete (cleaning tools etc) by 6PM last night.
Probably could have used a better method of removing the nut holding the piston on...but it worked (massive pipe wrench and a sledge hammer...I had to file the nut back down afterward). I completed the project 100% solo...with the help of the Bobcat, John Deer, and some flat straps. I did not remove any of the counterbalance valves at all. I used the hydraulics to do the work....I was a little nervous removing the end cap as I had extended the rod out completely. After recognizing that there was immense pressure and I was staring down the barrel of a hydraulic oil bath, I backed the cylinder off past the retract port which removed a considerable amount of pressure. Once the cap was removed, I used the hydraulics (thanks Bill) to push the rod out. Off course hydraulic oil went everywhere (which I figured would occur) even though I had 3 different catch basins. I did boom the machine up to save some of the oil. Inspection of the cylinder, rod, piston was all beautiful. I cleaned everything obsessively, greased the crap out of everything, and installed all components and seals exactly the way they were removed. I did booger up the interior of the end cap a little (thinking it was much like a race in a wheel bearing) and sanded any dings down for a smooth surface. This was my only mistake. Once I inserted the piston end into the cylinder as far as possible by hand, I removed the grease fitting at the end of the rod, covered it with towels, and used the John Deere (in low gear) to incrementally push the rod back into the cylinder far enough to be able install the end cap. I then used the hydraulics to push it back into the cylinder (once again incrementally) and reattached the end cap using the sequence I read in one of the other Lull repair manuals. I have the machine fully boomed up this morning to verify that the counterbalance valves are still functioning properly. I still need to replace the fluid that was lost as the supply house did not have AW68.
But that is all she wrote for my first ever cylinder repair!
Thanks again to you both for all of your help!
If you are ever this way, look me up and I'll buy you a beer or two. You can see what I use the machine for on my website www.theprecisionconstructiongroup.com.
Thanks again, fellas!
Rick
 
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carpentervin

Member
Joined
Aug 24, 2013
Messages
5
Location
Baton Rouge, La.
Lull 644-D Highlander

Good morning Bill and Joe!

I could use your help again if possible. I have purchased the OEM boom hoses from a local supplier and have a quality mobile heavy equipment mechanic ready to assist. Can you please provide some insight. One of the local shops stated that I would have to take the boom down completely. Will need the machine on site in 1.5 weeks and a previous arrangement to change has fallen through.

Any help is much appreciated!

Rick
 
joestewart

joestewart

Well-Known Member
Joined
Oct 14, 2009
Messages
204
Location
Lafayette, LA
carpentervin said:
Good morning Bill and Joe!

I could use your help again if possible. I have purchased the OEM boom hoses from a local supplier and have a quality mobile heavy equipment mechanic ready to assist. Can you please provide some insight. One of the local shops stated that I would have to take the boom down completely. Will need the machine on site in 1.5 weeks and a previous arrangement to change has fallen through.

Any help is much appreciated!

Rick
Click to expand...
I've never replaced those hoses before, but according to the manual, you do not have to disassemble boom. Do you need me to scan the pages in the manual and send them to you? Let me know.
 
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