This is a 2 stage free lift.Problem is, Center lift cylinder doesnt hold above 3000 lbs. center cylinder will fall slowly,Causing outer cylinders to raise. Once center lift cyl. has droped.Outer cylinders hold load,do not leak down. Thank for any help, Kent
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Know I haven't been servicing this lift.they bought it.then realized the problem.ive been wondering about that,also.we've tried contacting the guy it was bought from.but haven't been able to.the problem you Speek. of,seems very close.
Have you been servicing this lift before this issue started or is this the first issue you're servicing on this lift?
Reason for this question is- are you sure the main hoist cyl hasn't been altered/replaced?
I have a triple stage lift I service where the bottom of the main barrel got dented- the cyl had the packing at the bottom of the ram only w/ only a wiper in the upper gland nut. With the barrel being dented the ram wouldn't go past the dent, keeping the forks raised about 6". I had my hydraulic vendor re-machine the gland nut for a full packing & removed the packing from the bottom of the ram. After this alteration the ram went fully down, past the dent & the upright worked great, as long as you didn't mind the secondary cyl's raising first w/ the main cyl extending only after the secondary channels were fully extended.
Had to revert the cyl back to it's original configuration & have a new barrel made. Is it possible someone tried the same scenario on this upright?
Ill check that.I dont see how it could be in control valve.With outer cylinders holding,not leaking down.The main pressure line tees off threw that block,supples all 3 cylinders.I thought that block ,had to do with hyd. cusion for the lift cylinders.I was going back to work on it today,but I want to be able to fix it this time.The owner is very understanding.Still yet,I want to be more noligable about how this system works.Thanks Kent.
not sure if that manifold block has a check valve in it
after looking through several manuals for the duplex limited full freelift system and the troubleshooting guide it keeps referencing to check the relief valve on the control valve.
Could have a broken or weak spring or something in it or possibly a bad spool.
That's a full free lift duplex mast and I believe that valve is called a flow control valve. I think that is the only thing that can cause that problem because the lift cylinders are all the kind with just seals in the gland nut and no piston on the end of the rod.
GDPO60LCN2BF086/N543408. Yes it has the valve block attached to the back of the cross member.The main pressure line from the control valve enters on the bottom side of this block.The free lift cylinder hyd. hose attaches on top.{fluid to the free lift goes stright threw.There is a valve inside the block}.Theirs a valve comeing out the left of it.The two outer cylinder hyd.lines hook up here.Ive had this block off,an apart.Cleaned inside and reassembled,didnt see a broking spring,or any damage.It can be shimed at spring.but not seeing any problem.OR knowing for sure how it worked.I didnt want to change anything..
Hi Kent,
Have you got the rest of the model No of this truck,
Is it a GDP060 AB/TD/AF is it quite an old truck, dose it have a valve block screwed to the cross member at the back of the mast, if it has then there's a good chance that this valve has failed, I have experienced the cone shaped piston in this valve breaking up. Looking in an old w/shop manual this valve is referred to as the lowering valve but is not part of the main control valve.
we can guess at this all day long
but we need a full model number to give you any accurate information
but from what i remember on these masts the valve at the base of the freelift and left main cylinder is called a 'lowering control valve'.
It's function is to catch the load and limit the lowering speed in the case of a ruptured line. It is a safety valve. It has no bearing on how the load is held while the mast is raised.
From the diagrams i found on a 2 stage limited freelift mast the freelift (center) cylinder does have seals on the base of the piston and a flow control valve in the piston. But i did see a note that some 2 stage masts did not but there is one in the main left cylinder piston. From what i read that valve is there to allow a certain amount of fluid to pass to the top side of the piston packing to allow for some cushioning when full raised.
The troubleshooting section did speak of faulty seals in the cylinders or a possible faulty control valve. And as was suggested installing a gate valve between the control valve and the mast was the method used to determine where the leak was.
now with all that said there is still a slim possibility that this mast is a special mast not made by yale but that is rare.
Without a complete model number (and serial number) we're all just guessing here.
What is the year of manufacture of this lift? I haven't seen a standard ram type hoist cylinder in some time- since the early 80's I think?
Does anyone have a service manual for this.Im still trying to figure this out.their useing it,It lifts with the outer cylinders.
I Took the cylinder apart this morning.Ram is solid on bottom ,no valve,or lower packing.Also took the velocity fuse apart.{ hyd.fitting in lower cylinder}Looks fine.Their is a flow valve in this fitting.I dont know just what this fitting is for.Other than inlet for hyd. fluid.I had orderd a new one,but its on back order for 3 weeks.
I've learned the hard way that I always quote flushing the hyd system & replacing whatever filters are installed in cases like these where it's unclear until dis-assembly what actually happened
not really a check ball, is a check valve but made a little bit different
they usually are not servicable, you have to replace the valve
If you take the ram out and the valve is gone it's probably in the bottom of the cylinder beat all to pieces and you will have to fish out the pieces and hope none went back up into the lines.
Thanks.Ill check that.Its basically a check ball / seat deal,right. Kent
Sounds like the valve in the bottom of the free lift cyl is faulty.
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