HOW TO CHECK LIFT CYLINDERS???

TNHOTROD · Dec 16, 2008

WHATS THE BEST WAY TO CHECK THE LIFT CYLINDERS ON A 763???
I HAVE RESOLVED THE OTHER PROBLEMS WITH ALL THE HELP AND MILLION QUESTIONS I HAVE ASKED.. I FOUND A COUPLE OF THE SMALL BLACK HOSES GOING TO THE CONTROL VALVE IN THE WRONG PLACE AFTER LOOKING AT ANOTHER 763 LIKE THIS ONE.. SOMEONE ELSE HAD BEEN WORKING ON THIS MACHINE AND HAD PUT IT BACK TOGETHER INCORRECT... AFTER REMOVING THE CONTROL VALVE SEVERAL TIMES FROM THIS MACHINE I THINK I COULD PUT IT BACK TOGETHER WITH MY EYES CLOSED..

Tazza · Dec 16, 2008

First of all, see the caps lock button? ensure its NOT on, lower case is all that is required, in the internet world caps are known as shouting. I hate to be the one to bitch, but PLEASE don't ask a question in one post then start a new thread with the exact same question. It won't speed things up at all, it will only anger other members of the forum that are trying to help you out.
Ken has posted his technique multiple times to do this in other threads. Essentially he uses compressed air on one side of the cylinder, if you can hear air bubbling on the other side you know your piston seals are bad. If you think they could be bad you can swap them pretty easily, they are cheap too.
Be patient, you will get all the bugs out of your machine. You have been doing pretty well so far!

TNHOTROD · Dec 16, 2008

Tazza said:
First of all, see the caps lock button? ensure its NOT on, lower case is all that is required, in the internet world caps are known as shouting. I hate to be the one to bitch, but PLEASE don't ask a question in one post then start a new thread with the exact same question. It won't speed things up at all, it will only anger other members of the forum that are trying to help you out.
Ken has posted his technique multiple times to do this in other threads. Essentially he uses compressed air on one side of the cylinder, if you can hear air bubbling on the other side you know your piston seals are bad. If you think they could be bad you can swap them pretty easily, they are cheap too.
Be patient, you will get all the bugs out of your machine. You have been doing pretty well so far!

sent it from my phone did not even know it was caps,, hopefully its not on now...ken ... who is ken??? got a link not seeing it...
thanks for your help...

Tazza · Dec 16, 2008

TNHOTROD said:
sent it from my phone did not even know it was caps,, hopefully its not on now...ken ... who is ken??? got a link not seeing it...
thanks for your help...

Ken is skidsteer.ca
I'll see if i can russle up some of his posts on this.

Tazza · Dec 16, 2008

Tazza said:
Ken is skidsteer.ca
I'll see if i can russle up some of his posts on this.

http://www.skidsteerforum.com/DesktopDefault.aspx?tabid=54&frmView=ShowPost&PostID=3414
Its about 1/3 the way down but here are the highlights:
**************************************************************
I'd be unhooking and capping the hoses to one cylinder, then the other. Lift the boom with just one cylinder conected to the system and see if you creep is still there. If it gone try switching cylinders, see if the other side creeps.
If it goes away with once of the cylinders disconnected then it is likely a piston seal. If you think this is the case remove the suspect cylinder. CAP (seal off) the port farthest away from the chrome shaft. Hook your air compressor to the port that world retract the ram, and put the air to it. If the cylinder is good the ram will re tract and stay retracted. If the piston seal is leaking it will retract , then begin to extend. This is a definite indication of a internal piston seal leaking.
If un hooking one cylinder then the other makes no difference then I would go after the control valve if I cannot find any lines or hoses leaking.
With the valve I'd start by unhooking the hoses to both cylinders and capping the hoses on one side.
I'd connect my trusty 3000 psi guages , one to each of the lines that was connected to the second cylinder. Start the engine and step on the lift pedal.. The guage on the lift side should come up to what ever your relieve valve pressure setting is. say 2500 psi, when you release the pedal it should stay there if there are no leaks or valve problems.
In my expierence with load checks, they don't creep when the valve spool (control pedal) is in the center (neutral) position. I have a problem with the one on the tilt circuit of my 553. It hold fine until I move the pedal slightly from center, then the bucket starts to slowly dump even though I'm pushing with my heel, (curl bucket) until I push the pedal enough that the hyd pump starts putting oil in the cylinder, then the bucket comes up. It stays put fine as long as I don't move the pedal slightly off center.
****************************************
He did also mention using compressed air as a way of testing cylinders, use it on one side and listen for gurgling or foam.

mllud · Dec 16, 2008

Tazza said:
Ken is skidsteer.ca
I'll see if i can russle up some of his posts on this.

This is a recent post of Kens on tilt cylinders. I think this is what Tazza is talking about.
Cylinder bypassing the piston internally?
The test, unhook the hoses, push the rod in and out to remove most of the oil. Plug the port on the barrel end of the cylinder, and take the pin out of the rod end, hook your air compressor to the port on the rod end and pressurize it. If the packings are good the rod will retract into the cylinder and STAY there. If the cylinder is bypassing, the rod will retract then begin to extend itself.
As the air bypasses the piston it moves from the rod side that has a smaller piston area to the backside, since the piston has more area on the back side (becasue the chrome rod is eating up the usuaable area) and the back port is plugged the pressure equalizes on both sides of the piston but the back has more area so the rod extends out of the barrel
If the cylinder passes this test then its your load check (unless you have a external leak)
Ken

Re: 763 lift arms won't stay up
Posted: 12/11/2008 02:58 PM

The piston seals on one or both of your lift cylinders is leaking past, or it can be the control valve the foot pedal attaches too.
You can pressure test the seals on the cylinder piston with compressed air and see if they are sealed or bypassing the piston and escaping out the opposite port on the barrel.
If the pistons are sealing. then hook a 3000 psi pressure guage to the hose that goes to the back end of the cylinder and plug the hose going to the opposite side of the machine on the back end of that cylinder.
Start the machine and push the pedal to lift the boom. The guage pressure should rise (the boom should not lift if you hooked into the right hose and plugged the other one) to about 2250 to 2500 psi and stay near there when you release the pedal. If the pressure drops back down to 0 you have a problemwith a internal leak in the control valve or a bad hose. (the hose is unlikely because you would notice the oil leaking out everywhere)
Ken

mllud · Dec 16, 2008

mllud said:
This is a recent post of Kens on tilt cylinders. I think this is what Tazza is talking about.
Cylinder bypassing the piston internally?
The test, unhook the hoses, push the rod in and out to remove most of the oil. Plug the port on the barrel end of the cylinder, and take the pin out of the rod end, hook your air compressor to the port on the rod end and pressurize it. If the packings are good the rod will retract into the cylinder and STAY there. If the cylinder is bypassing, the rod will retract then begin to extend itself.
As the air bypasses the piston it moves from the rod side that has a smaller piston area to the backside, since the piston has more area on the back side (becasue the chrome rod is eating up the usuaable area) and the back port is plugged the pressure equalizes on both sides of the piston but the back has more area so the rod extends out of the barrel
If the cylinder passes this test then its your load check (unless you have a external leak)
Ken

Re: 763 lift arms won't stay up
Posted: 12/11/2008 02:58 PM

The piston seals on one or both of your lift cylinders is leaking past, or it can be the control valve the foot pedal attaches too.
You can pressure test the seals on the cylinder piston with compressed air and see if they are sealed or bypassing the piston and escaping out the opposite port on the barrel.
If the pistons are sealing. then hook a 3000 psi pressure guage to the hose that goes to the back end of the cylinder and plug the hose going to the opposite side of the machine on the back end of that cylinder.
Start the machine and push the pedal to lift the boom. The guage pressure should rise (the boom should not lift if you hooked into the right hose and plugged the other one) to about 2250 to 2500 psi and stay near there when you release the pedal. If the pressure drops back down to 0 you have a problemwith a internal leak in the control valve or a bad hose. (the hose is unlikely because you would notice the oil leaking out everywhere)
Ken

Tazza I was searching for kens post and I guess you posted in between. I didnt see you already posted. Mike

TNHOTROD · Dec 17, 2008

mllud said:
Tazza I was searching for kens post and I guess you posted in between. I didnt see you already posted. Mike

Well i (thought) i had fixed the lift arm drift problem but i guess i have not. After putting the bucket back on i have now found that it still drifts down slowly and the tilt cylinder is drifting also slowly. i have the kits to do the lift arm cylinders but have not done them yet. Is it possible if the lift arm cylinders are leaking that the tilt cylinder would drift also???
Any suggestions or help???
thanks for all the help

skidsteer.ca · Dec 17, 2008

TNHOTROD said:
Well i (thought) i had fixed the lift arm drift problem but i guess i have not. After putting the bucket back on i have now found that it still drifts down slowly and the tilt cylinder is drifting also slowly. i have the kits to do the lift arm cylinders but have not done them yet. Is it possible if the lift arm cylinders are leaking that the tilt cylinder would drift also???
Any suggestions or help???
thanks for all the help

Not in any way I can think of. They should both be isolated from each other.
Pressure test the cylinders to see if they are sealed or not. Bad poly packs (cylinders seals) can leak on one lift cycle and not on the next also. As the packing tears apart pieces can block the leaking hole on one cycle of the cylinder and then leave it open to leak on another cycle. You had stated the main lifts were re packed? Air test them and see if they are sealed or not.
Ken

Tazza · Dec 17, 2008

skidsteer.ca said:
Not in any way I can think of. They should both be isolated from each other.
Pressure test the cylinders to see if they are sealed or not. Bad poly packs (cylinders seals) can leak on one lift cycle and not on the next also. As the packing tears apart pieces can block the leaking hole on one cycle of the cylinder and then leave it open to leak on another cycle. You had stated the main lifts were re packed? Air test them and see if they are sealed or not.
Ken

As ken said, the 2 circuits are not linked in that way. Both lift cylinders are in parallel but not linked to the tilt. The only common point both have is the high pressure oil suply, but when the spool is in the centre the fluid is held in place, or should be and they are isolated.

TNHOTROD · Dec 17, 2008

Tazza said:
As ken said, the 2 circuits are not linked in that way. Both lift cylinders are in parallel but not linked to the tilt. The only common point both have is the high pressure oil suply, but when the spool is in the centre the fluid is held in place, or should be and they are isolated.

I have had a couple of people say something about the aux. stems and coils .. all three stems and coils have been replaced with new ones. a couple of people have said something about the stems looking similar but the diameter being different causing problems.. Anyone ever seen this problem????

Tazza · Dec 17, 2008

TNHOTROD said:
I have had a couple of people say something about the aux. stems and coils .. all three stems and coils have been replaced with new ones. a couple of people have said something about the stems looking similar but the diameter being different causing problems.. Anyone ever seen this problem????

I can't see it being your aux system causing the problem. I'd start by by re-packing the cylinders first.

TNHOTROD · Dec 17, 2008

Tazza said:
I can't see it being your aux system causing the problem. I'd start by by re-packing the cylinders first.

both or all three???????

Tazza · Dec 17, 2008

TNHOTROD said:
both or all three???????

I'd do all 3, they are cheap.

TNHOTROD · Dec 18, 2008

Tazza said:
I'd do all 3, they are cheap.

what would happen if the port relief/anticavitation stems got switched around in the control valve?? one is just port relief and one is a optional port relief anticavitation together???

Tazza · Dec 18, 2008

TNHOTROD said:
what would happen if the port relief/anticavitation stems got switched around in the control valve?? one is just port relief and one is a optional port relief anticavitation together???

It is possible.....
It wouldn't hurt to check it, there have been so many things wrong so far i'd check it out. It may be a combo anti-cav relief, a lot have gone this way.

TNHOTROD · Dec 18, 2008

Tazza said:
It is possible.....
It wouldn't hurt to check it, there have been so many things wrong so far i'd check it out. It may be a combo anti-cav relief, a lot have gone this way.

i know there are two that are the same and one that looks the same it just has a small hole down towards the end .. are the bics cartridgesthe same on both sides???

thanks chris

HOW TO CHECK LIFT CYLINDERS???

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