• If you like antique engines, vintage tractors or old iron, please register and join us. When registering, please provide your CITY and STATE as your location!

Daewoo Forklift - Lift Cylinder Repair

dalmatiangirl61

Subscriber
Last Subscription Date
07/10/2019
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:shrug:. 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?
 

Attachments

europachris

Registered
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
 

Russell Walker

Sponsor
Last Subscription Date
08/25/2019
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.
 

dalmatiangirl61

Subscriber
Last Subscription Date
07/10/2019
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.
 

I like oldstuff

Registered
Last Subscription Date
11/09/2015
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.
 

Russell Walker

Sponsor
Last Subscription Date
08/25/2019
There should be no hyd. fluid at top. if there is it is leaking past piston which is normally on bottom of the ram.
 

Turbo

Subscriber
Last Subscription Date
07/12/2019
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.
 

Ifix71

Subscriber
Last Subscription Date
02/04/2020
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
 

LCJudge

Subscriber
Age
60
Last Subscription Date
12/14/2019
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.
 

dalmatiangirl61

Subscriber
Last Subscription Date
07/10/2019
Its ok Russell, I've never seen one like this either. Went up and looked at it again, and had 2 others look at it to verify. Pic 1 base of cylinder front. Pic 2 base of cylinder back, hyd hose in both pics is the one going to center of cylinder wall. Pic 3 Top of cylinder, big nut with flats for a wrench. Note the port boss on top right of cylinder, it has what looks like a brake bleeder valve. Pic 4 top of ram, pretty sure that all unbolts and can be set to side.

As long as I can break the nut free without pulling the whole cylinder, I'm kind of liking this design. Did right side steering cyl on the JD (again) last week, and was not looking forward to wrestling with a rod 3 times longer/heavier.
 

Attachments

CharlieB

Registered
Having never seen on of these, I'm still trying to get my head around the concept. ????
I get that the entire cylinder is pressurized to move the ram. How does the pressurized oil get to the bottom of the cylinder to exert force on end of the ram? Is there clearance between the ram and the cylinder to allow oil to pass? If so, what keeps the ram from wobbling in the tube? I get that this design eliminates the cost of seals on the end of the ram, but what is the advantage of introducing the oil at mid-stroke instead of at the bottom of the cylinder?
 

Toesmack

Subscriber
Last Subscription Date
02/08/2019
Dalgal, europachris and several others got it right. Notice the ram is only slightly smaller than the outer cylinder tube. There is not a piston as we might know it, just a guide at the bottom of the ram to keep it aligned, and keep you from blowing it out of the cylinder. The ram IS the piston. The upper gland nut and seal is the only pressure seal required. The bleeder nut is to remove the air trapped inside the hollow ram. If you raise the whole thing about 6" and throw a wood block under the fork fence, you should be able to slack out the chains enough to pull the roller head without breaking the chains. Hopefully the packing nut will turn with a chain wrench, it should be o ring sealed so does not require thousands of ft lbs of torque.

Charlie The only real advantage of the inlet being so high is in getting the lines and fitting up higher on the machine where damage is less likely. Really doesn't matter where you squirt the oil in, it still figures out which way to go.
 

CharlieB

Registered
Aha. So there is a guide at the bottom of the ram/piston to keep it centered and still allow oil to pass. Is this a wear part that should be replaced along with the seal at the top? If not, it looks like a big advantage to this system is that you don't have to remove the ram during overhaul. I hadn't considered that the ram might be hollow (and open at the bottom end?) That would mean that the pressurized oil pushes against the top end of the ram instead of the bottom, greatly reducing the compression force on the ram. I guess that means that there would be bleeders at the tops of both the cylinder and the ram. I think I get it now. Thanks for your help, Toesmack.

To dalmationgirl. My apologies for temporarily hijacking your thread. Good luck with your project.
 

dalmatiangirl61

Subscriber
Last Subscription Date
07/10/2019
Charlie, its not hijacking, this style ram is clearly new to a few of us. I had looked at it for a week before posting here, needed to make sure my thinking was not crazy.

Ordered a seal kit today, Doosan carries parts for the Daiwoo line, all they needed was model & serial numbers. $36 + tax and shipping and it should be here Thursday. Might have been a little cheaper at the parts counter at a hydraulic shop in SA or Austin, but I really try to avoid going to either one of those towns, its a traffic nightmare and can be an all day trip.

Out of curiosity I wondered what happened to Daiwoo and did a little looking into it, here is the Wiki page https://en.wikipedia.org/wiki/Daewoo they went bankrupt in 1999, about 84 billion in US dollars in the hole:eek:. The heavy industry section became Doosan, and the automotive section is now owned by GM, and marketed under the Holden name in Australia and several other countries.
 

Heins

Subscriber
Last Subscription Date
01/02/2020
Truck hoist have been built like that for years. Most are telescoping (one ram inside another) and are sealed at the top. At the bottom part of the ram there usually some brass on the ram about 1 or 2" wide that will just fit inside the barrel to guide the ram inside the barrel. It will have some places in the brass to let the oil go by.

D-Girl, I think you have it figured out.
 

Heins

Subscriber
Last Subscription Date
01/02/2020
Here are two pictures of hydraulic cylinders, the first is our old fork lift. It has a three stage cylinder. The oil goes in at the bottom, the line you see at the top of the cylinder is a leak off line. There are only two stages out.

The second picture is of a truck three stage hoist cylinder. You can see the end of the ram, it is the same size as the rest of the ram that goes through the seal.

The brass at the end of the ram is larger than the rest of the ram. It hits the part that holds the seal so the ram doesn't blow out of the cylinder.
 

Attachments

dalmatiangirl61

Subscriber
Last Subscription Date
07/10/2019
Nice sunny day today so I worked on the Daewoo. Pic 1 Load guard removed and a jack stand under fork carriage, had to stand on top of cylinder while friend pulled lever to get it to lower so there was slack in chains. Pic 2 Gland nut removed, used the chain wrench. Pic 3 seals replaced and gland nut back on, even though rod has a good bevel, it was a pia getting new seal over rod, solution was a piece of pipe over rod, then levering with a 2x4 against steering wheel. Pic 3 being a hard tire lift I guess mfr thought this machine would live indoors so there was no cap to cover top of cylinder, decided to make a cap for it and this little ss bowl fit just right. Should keep out most of the rain, the ever-present dust, and reduce UV exposure to the wiper seal which is exposed.
 

Attachments

dalmatiangirl61

Subscriber
Last Subscription Date
07/10/2019
Pic 1 the new dust/rain/UV cap installed and lift ready to test. Pic 2 it all works great, dust cap just clears the chains and hoses, and drops right over cylinder every time.

Next up is the side shift cylinder, need to give that area a good bath before tearing into it.
 

Attachments

Top