Yale GDP050TENUAE086:
hydraulic problem with mast

Sometimes the second mast section starts to raise before the first one has reached it's limit. The top sections can also stay extended too long as you are lowering the forks. As the lower section starts to lower, the top sections will free fall slightly to catch up.

I am thinking it's a valve sticking, causing the pressure not to divert properly. Does someone have more info? If it is a valve, where is it located (in the union connection?)

If you extend the mast fully before you start to use it, it seems to work ok. It has plenty of oil, looks pretty clean. Haven't tried changing the filter, since the pressure seems fine.
  • Posted 13 Apr 2007 09:21
  • Discussion started by Suzi
  • Texas, United States
Showing items 1 - 11 of 11 results.
The rail comes up before the carriage does and the only way to get it to work properly is taken all the way up and then back down again it'll work about two times then it goes back to the same situation the rail comes up and the carriage don't
  • Posted 20 Sep 2022 20:56
  • Reply by David_Southerly
  • Virginia, United States
David
Hello,

I have a similar problem with a Toyota 02-8fgu series 2008.
In the lifting command , sometimes the center free lift cylinder ,is rising for 1-2 cm and stop,... then 2 stage cylinders is rising.
The second problem is , when the free lift center cylinder is rising first , then you stop the command , then when you look careful this cylinder slowly descends.
Maybe the problem is from the same place. the check valve from the cylinder????

If it were just a mechanical advantage,when you have the load in the fork, would not lift the first "free lift" cylinder and the oil would be directed to the other 2, so it must be a condition to keep the pressure in the first cylinder
Regards !
Gabi
  • Posted 6 Oct 2017 08:27
  • Reply by gabi_g
  • Ontario, Canada
gabihdh at gmail dot com
This may or may not help. We had a Toyota 3 stage with the exact same problem. A real gremlin. We replaced the hydraulic line to the 2 stage cylinders and it solved the mystery. for some reason it was causing the cylinders to work out of sequence. This may be cheaper than resealing the cylinders. Hope this helps
  • Posted 22 Aug 2008 07:00
  • Reply by Prentice
  • Ontario, Canada
IF this has not already been fixed. The freelift cylinder needs to be disassembled, the small black shuttle valve in the bottom of the ram needs to be replaced, it is held in by a small snap-ring. If this valve is not opening freely it will allow the fluid to build around the positively displaced ram and fool the hoist cylinders into thinking it is full extended. This valve allows the hydraulic fluid to escape from the topside of the piston as the cylinder extends.
I guess in "internet time" on forums like this, that makes it often safe to _ass_u_me_ the last post must have fixed the problem?
my problem in "self help" internet forums is to read far enough into the thread before I shoot off and try the first or second suggestion that sounds like it makes sense. I bought some real crap and made a huge mess trying to get some linoleum flooring up in my kitchen once....

;-)
  • Posted 21 Jul 2008 00:00
  • Modified 21 Jul 2008 00:03 by poster
  • Reply by edward_t
  • South Carolina, United States
edward_t is correct in his assumption that they may have already fixed this since there has been so much time elapsed since the first post. And yes it would be nice if users would come back and post thier findings for all to see. It might actually help someone else but unfortunatly in this fast paced world who as time? know what i mean? nobody wants to take the time to follow through unfortunatly.
  • Posted 20 Jul 2008 23:52
  • Reply by Jplayer
  • North Carolina, United States
John Player Jr
_________________
LiftOne, LLC
Charlotte, NC
Email: jplayer@liftone.net
a couple of questons, when the lift is staging improperly, if you run the lift to it's maximum length up, does it then start staging correctly? is it only in the lifting action that the sections travel improperly, or do you sometimes only have a problem lowering?

my instant guess is the seal in the center (first stage) lift cylinder on the piston is allowing bypass oil to get above the seal, (usually when just sitting and no weight or pressure is against the seal, so noticing this early in the day or ju8st after lunch?) and until the oil is forced back to the correct side of the seal by fully lifting.
The reason one set of cylinder lifts before the other set is not a valve it is called "mechanical advantage" that while the load is shared by all the cylinders, the center cylinders have an slightly easier time lifting is why they move up first, not some "cylinder lowering control valve" that controls the mast staging.
The valves you might see at the bottom of a lift cylinder are more likely to be what I call a velocity fuse, where if a lift hose were to break or other wise loose all pressure, the fuse would prevent full speed dropping of the load.
have someone else that the forklift tech you had look at it in the past, and get their price on repacking the center lift cylinder.


VerticalVicDude, I am not too sure your method of answering is all that clear or correct. you write;

Q//? I am thinking it's a valve sticking,(That's Correct)

I am not so sure it's correct...
and since to original post was dated 13 apr 2007, hopefully they got this fixed, and maybe will come back and let us all know what the problem really was...
  • Posted 20 Jul 2008 20:54
  • Modified 20 Jul 2008 20:57 by poster
  • Reply by edward_t
  • South Carolina, United States
Q//?
I am thinking it's a valve sticking,(That's Correct) causing the pressure not to divert properly. Does someone have more info? If it is a valve, where is it located (in the union connection? (Yes It is)

A//
Bad Lowering Control Valve (Inside Lift Cyl second stages) and Lowering control valve (OUTSIDE located at free lift Cyl, a built-in mast fittings. in the union connection) could be any of this 3 valves. my best guess... take a look to a valve located at free lift cyl in the union connection using a Double Pointed Scriber to cleand-up or cause to change the actual condition.
  • Posted 20 Jul 2008 13:53
  • Reply by VerticalVicDude
  • California, United States
Victor Alvarado
Ok suzi,
you say they replaced the center seal 1yr ago?
ok that might be a place to look again.
The way the hydraulic system works on the mast is it is an equalizing type system, when you actuate the lift it sends fluid to the cylinders and if all is well the primary cylinder (center) is supposed to raise first, when it reaches it's max height and bottoms out the secondary cylinders take over. If there are no restrictions in the system this is how it is supposed to work.
If your center channels are raising prematurly then the center cylinder is restricted for some reason causing the fluid to divert to the secondary cylinders prematurly.

There are 2 things i would check
First of all i would have the primary (center) cylinder rechecked to make sure the packing in the gland nut isnt dry or has blown out and is causeing a bind against the rod.
Or even a small possibility that they installed the incorrect seal kit and it's just too tight causing the center cylinder to stick.

Second is there should be a small manifold block mounted about waist high on the back of the stationary channel between the mast and the cowl of the lift frame. (inbetween the mast and the truck) it should be mounted on the mast cross bar and has hoses or metal tubes running from it to the cylinders.
Pull the hoses and check inside this block for restrictions of any kind. If it has a check valve, check that for debis or being stuck.

Note: when they sourced the packing kit for the cylinder seal kit they should have looked on the cylinder, there is a cyllinder number group etched into the cylinder shell, usually somewhere on the side of the cylinder shell. You may have to clean it off to see this.

Hope this helps

Later,
  • Posted 13 Apr 2007 12:16
  • Modified 13 Apr 2007 12:24 by poster
  • Reply by Jplayer
  • North Carolina, United States
John Player Jr
_________________
LiftOne, LLC
Charlotte, NC
Email: jplayer@liftone.net
It's a Yale 5000 with a 3 section mast. We had a forklift company take a look at it and they just scratched their heads. They soaked the tracks down with lubed and checked the channels - said they looked ok. We bought the machine used about 5 years ago, treated pretty easy. Had the seal replaced in the center cylinder a year or so ago. It was leaking.

I think it would be with the hydraulics because the upper mast sections begin to move up before they are suppose to. (before the lower section reaches it's full extention)
  • Posted 13 Apr 2007 11:59
  • Reply by Suzi
  • Texas, United States
Hi Suzi,
you may want to double check the mast channel tracks where the rollers run and make sure there is no type of debris or dirt. Also check the thrust sideplay in the mast channels and see if there is any movement from side to side. If there is no movement your channels may be too tight inside thier respective tracks. I have seen this before and sometimes scraping the roller track helps, even applying some lube where you see rubbing inside the tracking area. I know a roller track doesnt require lube due to the nature of the beast, grease and rollers tend to cause the roller to slide and wear flatspots on the roller but in some cases this may be the only solution to your problem for the time being till the mast wears in some.

Is this a new machine? If so what type mast does it have?
make model of truck?

If there are any adjustable side wear plugs check those and make sure they arent too tight.
  • Posted 13 Apr 2007 11:22
  • Reply by Jplayer
  • North Carolina, United States
John Player Jr
_________________
LiftOne, LLC
Charlotte, NC
Email: jplayer@liftone.net

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