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Lifting and Loading

Daewoo Forklift - Lift Cylinder Repair


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  #1  
Old 03-26-2018, 05:16:16 PM
dalmatiangirl61 dalmatiangirl61 is offline
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Default Daewoo Forklift - Lift Cylinder Repair

The main lift cylinder on the Daewoo forklift is leaking at top of cylinder (I can see a gap in the seal), generally I know how to repair cylinders, but this one has me scratching my head. There is only 1 hose going into this cylinder, instead of going into base, it is going into the side of the cylinder at about the mid-point. The rod is clearly long enough that the piston would travel past the port, soooo, I'm just not getting it. If fluid is traveling along the side of rod, and going thru the piston (holes?/valving?), can I just pull the nut and slide it over top of rod and replace the seals in the nut?

Single hose/port into cylinder is middle of pic on first 3 pics. Fourth pic shows rod at full extension, its a solid rod, not telescopic.

Anyone understand what is going on here?
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  #2  
Old 03-26-2018, 05:33:06 PM
europachris europachris is offline
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Default Re: Daewoo Forklift - Lift Cylinder Repair

It's possible the rod doesn't have a piston. There would be a guide at the bottom of the rod to keep it aligned in the bore, but it wouldn't seal to the bore. The oil would be able to enter in the middle of the cylinder and pressurize the entire rod (bottom and sides) inside the cylinder, basically squirting it out of the cylinder like a watermelon seed. All of the pressure sealing is done at the top of the cylinder.

If this is actually how it's put together, it's rather uncommon. Unless the rod is hollow, it makes it much larger and heavier an a piston-style cylinder.

Chris
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Old 03-26-2018, 05:58:20 PM
Russell Walker Russell Walker is offline
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Default Re: Daewoo Forklift - Lift Cylinder Repair

There is a pipe or port from fitting to bottom of cyl. The seal you see is a dust seal at that point pull packing gland nut the one at top. let incoming hyd line have air and pull ram out of cyl. barrel seal you need is on bottom of the ram/center rod. Rod is real heavy. any good hyd shop will have new seals you need.
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Old 03-26-2018, 06:48:29 PM
dalmatiangirl61 dalmatiangirl61 is offline
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Default Re: Daewoo Forklift - Lift Cylinder Repair

Chris
That is what I'm thinking, but I've thought wrong before.

Russel
There is no external line to bottom of cylinder, I don't think wall of cylinder is thick enough to run port thru there, and a groove in the interior wall of cylinder puts us back to the space between cylinder and rod above piston being pressurized. Only other possibility I can come up with is that somehow they routed hydraulics thru base casting that cylinder base is bolted to???

In operation, it does not leak much while lifting forks, if forks get raised then left to sit it starts a fairly steady flow, when forks are lowered what ever is puddled on top of cylinder gets sucked back in. So far no shower of hydraulic fluid, just a steady seep. Looked at a similar Toyota lift mast last week, it had port at base of cylinder.
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Old 03-26-2018, 06:53:00 PM
I like oldstuff I like oldstuff is offline
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Default Re: Daewoo Forklift - Lift Cylinder Repair

I can't tell by the pics as we can't see the top of the cylinder and I could be wrong, but it may be a welded cylinder. Therefore the rod won't come out as the top fitting that serves as the bearing and travel limiter is welded onto the cylinder after the rod is inserted. The rod diameter is smaller than the cylinder ID so fluid flows freely. A one hose design just relies on gravity to push the juice back to the reservoir.

If this is the case and is a single acting welded cylinder, these cyls can often use a multiple layer disk seal. Imagine 8-10 paper disks stacked on top of each other then secured by a big nut or a washer and snap ring. Some of these seals are split so you can slide them over the shaft if there is an end feature on the rod that is bigger than the rod diameter. *Soak the new ones in oil for a day to soften them up before putting them on and stagger the gaps. They're pretty cheap. If this is whacha have and you can't get them from Daewoo, take your ID and OD measurements and stack height then trundle to the local hydraulics store.
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Old 03-26-2018, 07:01:10 PM
Russell Walker Russell Walker is offline
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Default Re: Daewoo Forklift - Lift Cylinder Repair

There should be no hyd. fluid at top. if there is it is leaking past piston which is normally on bottom of the ram.
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Old 03-26-2018, 07:07:10 PM
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Default Re: Daewoo Forklift - Lift Cylinder Repair

I have worked on a few cylinders like that before and there is no sealing piston, just the ram. On a single acting cylinder there really is no need to have a seal on the piston.
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Old 03-26-2018, 07:10:42 PM
Ifix71 Ifix71 is offline
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Default Re: Daewoo Forklift - Lift Cylinder Repair

This design is very common in forklift mast cylinders they are single acting the fluid pushes the solid shaft out of this cylinder at the top of the cylinder you will have a Gland nut holding the wiper and possibly the seal inside it otherwise the seal is under it you’ll have to have a tool like a wood screw in the end of slide hammer to pull it out many times the urethane seal will come out in crumbles caused by the detergents either in the soap washing the machine down or in the oil itself
Be sure and block the mast up properly before you attempt to take it apart
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Old 03-26-2018, 07:15:09 PM
LCJudge LCJudge is offline
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Default Re: Daewoo Forklift - Lift Cylinder Repair

Quote:
Originally Posted by europachris View Post
It's possible the rod doesn't have a piston. There would be a guide at the bottom of the rod to keep it aligned in the bore, but it wouldn't seal to the bore. The oil would be able to enter in the middle of the cylinder and pressurize the entire rod (bottom and sides) inside the cylinder, basically squirting it out of the cylinder like a watermelon seed. All of the pressure sealing is done at the top of the cylinder.

If this is actually how it's put together, it's rather uncommon. Unless the rod is hollow, it makes it much larger and heavier an a piston-style cylinder.

Chris
Chris, I have a TCM forklift and it works exactly as you describe. There is no seal at the "base" of the shaft. Rather, the oil filling the cylinder tube displaces the shaft causing it to be forced out the top. The top is the only place there is a seal for the cylinder. I didn't realize it was made and functioned like this until mine began to leak and I decided to fix it myself. I unscrewed the cap at the top of the cylinder and pulled the shaft out. There was no type seal at the bottom of the shaft. I took it to a local hydraulic repair shop and asked them what was the deal on it. They explained it and asked me to go get the tube and bring back to them. I went and took it off and they didn't have it back in their shop more than 10 mins and they brought it back to me repaired. The cost wasn't too bad, about $50 for parts and labor.
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Old 03-26-2018, 08:03:29 PM
Russell Walker Russell Walker is offline
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Default Re: Daewoo Forklift - Lift Cylinder Repair

Sounds like your machine is a lot newer than any I have worked on. Please ignore earlier post.
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