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sevenracer
sevenracer Reader
3/20/22 8:56 p.m.

My 3500 model quick jack blew one cylinder a few months ago. Would not lift that side, and red hydraulic oil infused foam coming out of the air cylinder when Schrader valve opened. I bought a new cylinder and went on with life. Yesterday, other cylinder did the same. 

No rebuild parts from quick jack, just new cylinders. Google shows nothing either. 

Here is the piston end. No hex head to unthread the end. There is a hole that kind of looks like a set screw, but does not appear to be one. Anyone seen this setup before? Can the end be removed in a non destructive way? I assume, new seals would solve the problem. 

 

WonkoTheSane
WonkoTheSane UltraDork
3/20/22 9:00 p.m.

If you're not in a rush, a friend runs North Central Service a hydraulics shop, https://www.ncs-inc.com, he can probably rebuild that.  Give them a call or send an email with pictures and they can probably guide you through what you need.

jgrewe
jgrewe HalfDork
3/20/22 10:08 p.m.

I would find a hydraulic shop near you if the one linked above is far from you. 99 times out of 100 they have the special tools and can do the rebuild in a day.  My local place charges about $100 for most cylinders that I can carry in.  They do tend to fail in pairs like yours did. I've had a few instances where one of a pair goes and the next week the other goes.

sevenracer
sevenracer Reader
3/20/22 10:31 p.m.

At this stage I was just hoping to learn how to get it apart. If special tools are the answer, then yeah I'll be sending it somewhere.

jgrewe
jgrewe HalfDork
3/20/22 11:02 p.m.

That is probably a hole for a C pin spanner wrench.

sevenracer
sevenracer Reader
3/21/22 4:10 p.m.

In reply to jgrewe :

Never encountered those before.

If I can get the right spanner, any reason not to try to unscrew the end off one of the dead cylinders and investigate - you know, for science laugh

Slippery
Slippery UberDork
3/21/22 4:44 p.m.

jgrewe
jgrewe HalfDork
3/21/22 7:57 p.m.

I would! Can't figure out how stuff works without trying to remove its guts. If you have a supplier for O rings I'm sure you could walk in with the old ones and match them up.

sevenracer
sevenracer Reader
3/22/22 8:34 p.m.
jgrewe said:

I would! Can't figure out how stuff works without trying to remove its guts. If you have a supplier for O rings I'm sure you could walk in with the old ones and match them up.

Unfortunately, I don't currently have an "O-ring guy", lol. But first things first, I ordered the spanner.

Also, really surprised to find zero hits on Youtube for rebuilding QuickJack cylinders. Seems like someone would have blazed this trail already.

californiamilleghia
californiamilleghia UltraDork
3/22/22 9:20 p.m.

Are there any good YouTube videos that shows how it's done ?

I would probably not end up doing it , but it's good to know what goes wrong so you can decide if something that's for sale is fixable , 

I really like those big long Hein Warner shop jacks , but most of the cheap ones are pretty old and leaky.....

Thanks

jgrewe
jgrewe HalfDork
3/22/22 11:24 p.m.

You don't need a business account at Grainger anymore. They will ship to you or to a branch near you. Looks like there are two branches in Charlotte. Their prices tend to be high but they have what you need.

Keep track of seal orientation and get out a dial caliper.

https://www.grainger.com/search?searchQuery=hydraulic+seals&searchBar=true

 

 

sevenracer
sevenracer Reader
3/23/22 10:14 p.m.

Ok, mostly disassembled...

The white spacer ring behind the cap o-ring is broken , but that should only help to seal the cap to the tube (which had no leaks) - and not affect actuation

The piston end has 2 seals and a hard plastic wear ring in the center. The green seal rings must have failed - there was a ton of oil in the dry side of the piston when I took the cap off.

Sealing ring has dimensions molded in:

The piston appears to be press fit on the shaft:

 

So, I think the green seals are the problem since lots of fluid made it to the other side. Should be easy enough to source and replace those. Obviously, best to replace all seals, but I think to do that I would need to press the piston off the shaft to be able to remove the cap from the shaft and replace its seals. The cap should have a seal and wiper for the shaft.

I'm kind of tempted to just replace the green piston seals and re-assemble. The cap seals have not been disturbed and were not causing problems. This avoids potential damage to the shaft when pressing the piston off and back on. I'd like to replace the broken white spacer on the cap, but it appears to be delrin or similar - i.e. not stretchy, so not sure how easily it can be installed - and certainly don't think it can be stretched over the piston and then the cap.

jgrewe
jgrewe HalfDork
3/24/22 12:27 a.m.

Are you sure the piston isn't threaded on the shaft? I would think a pressed fit on something that is used to press and pull on things might cause trouble.

I would go your route of replacing the green seals and leave the top seal alone at first. Now that you can pull it apart it will be easy the second time if it leaks. You will keep oil off of that side of the piston which leads to it being forced out when the ram is extended. No oil, no leak. Just wiping the shaft. Heck, it might only be a wiper seal in there anyway if it isn't a 2 way ram.

sevenracer
sevenracer Reader
3/24/22 9:10 a.m.

In reply to jgrewe :

Not sure how the piston is attached, but I'm not seeing any features in the piston to torque the piston down on a threaded shaft.

This is a one way hydraulic ram, but the dry side is pressurized with air to help retract the cylinder the final distance home when no weight is present on the jack (i.e. once the car is resting on its wheels). That's why I'm speculating that there is some type of seal in the cap in addition to the wiper.

TurnerX19
TurnerX19 UltraDork
3/24/22 9:17 a.m.

Do I see the end of a wire lock ring here?

WillG80
WillG80 Reader
3/24/22 9:19 a.m.

Search YouTube for hydraulic cylinder rebuild. There's a million videos of guys repairing their construction equipment cylinders. I'm about to rebuild the two lift cylinders on my skid steer, they're pretty simple. 
 

if you take the disassembled cylinder to the hydraulic shop they can measure and instruct on what to replace. There's a very good chance they have all the needed seals in stock. A cylinder rebuild kit it usually only $20ish so it's worth replacing all the seals while you're in there. 

hobiercr
hobiercr UltraDork
3/24/22 11:45 a.m.

I'm late to the game here but some additional info.

The green piston seals are called unloaded u-seals and they are installed in a double-acting orientation. U-seals can be designed in piston, rod, or symmetrical orientation. Frequently DA pistons use 2 symmetrical u-seals. You can tell by looking at the lip design. The part numbers on u-seals is Cross Section - ID - Height, so a 250-1000-500 would be 1.000 x 1.500 x 0.500 (IDxODxHt) seal. If the dimensions aren't on the seal (which yours are) you would want the metal dimensions to determine what you need (i.e. piston groove OD, Bore ID for IDxOD) and normally the height is from the seal itself.

EDIT: Your seals are a 1.5 (OD) x 1.125(ID) x 0.25 HT and possibly a piston seal design based on how they show the seal dimensions. Your CS is 0.1875 so a seal house would call that a 187-1.125-250. 

I doubt the wear ring sees much side loading so probably no reason to replace it. 

In the head there will be another seal (u-seal probably), possibly another wear ring and either a snap-in wiper (no can) or a press in (can) that looks a lot like an oil seal but with no lip spring. To replace these the shaft has to come apart somehow with the piston coming off (snap ring or threaded). The white ring that is broken is a Teflon back-up ring that helps the o-ring seal fluid in without extruding through the gap. This back-up ring can either be solid, skive cut, or spiral cut. Because yours is damaged it could either be a solid or a skive cut, hard to tell. 

To install any of these seals it will be important to lubricate them very well and even possibly heat them in oil, especially the teflon back-up ring as it has very little memory and won't snap back like the NBR o-ring or polyurethane u-seals.

in Charlotte there is a Wyatt Seal and HSC (Hydraulic Supply Company). Both should be able to get you what you need.

hobiercr
hobiercr UltraDork
3/24/22 12:04 p.m.
sevenracer said:

In reply to jgrewe :

Not sure how the piston is attached, but I'm not seeing any features in the piston to torque the piston down on a threaded shaft.

This is a one way hydraulic ram, but the dry side is pressurized with air to help retract the cylinder the final distance home when no weight is present on the jack (i.e. once the car is resting on its wheels). That's why I'm speculating that there is some type of seal in the cap in addition to the wiper.

Questions. Do you often use compressed air to retract the cylinder the entire way? If so, through the schrader valve or some other port? When lifting the jack, how does air escape the cylinder? 

jgrewe
jgrewe HalfDork
3/24/22 12:22 p.m.

In reply to hobiercr :

I bet gravity does most of the work with the car on it, then a little bit of air pressure to get past the friction of the seals.  It looks like the system holds some volume/pressure of air in the piggyback cylinder and the hydraulic pressure wins the battle to lift the car.

@ sevenracer- I would grab the small diameter end of the piston with a pipe wrench and see if it turns. 

sevenracer
sevenracer Reader
3/24/22 2:36 p.m.
hobiercr said:
sevenracer said:

In reply to jgrewe :

Not sure how the piston is attached, but I'm not seeing any features in the piston to torque the piston down on a threaded shaft.

This is a one way hydraulic ram, but the dry side is pressurized with air to help retract the cylinder the final distance home when no weight is present on the jack (i.e. once the car is resting on its wheels). That's why I'm speculating that there is some type of seal in the cap in addition to the wiper.

Questions. Do you often use compressed air to retract the cylinder the entire way? If so, through the schrader valve or some other port? When lifting the jack, how does air escape the cylinder? 

Jgrewe is correct. Weight of car does most of the work and there is a small chamber welded to the main tube that has a Shrader valve. Before using the quickjack, you set the pressure at about 50 psi with the Shrader valve to move it back the last little bit where there is no weight on the jack. The system maintains air pressure for months in my experience.

And thanks for all the info in your other post!

hobiercr
hobiercr UltraDork
3/24/22 3:04 p.m.
sevenracer said:
hobiercr said:
sevenracer said:

In reply to jgrewe :

Not sure how the piston is attached, but I'm not seeing any features in the piston to torque the piston down on a threaded shaft.

This is a one way hydraulic ram, but the dry side is pressurized with air to help retract the cylinder the final distance home when no weight is present on the jack (i.e. once the car is resting on its wheels). That's why I'm speculating that there is some type of seal in the cap in addition to the wiper.

Questions. Do you often use compressed air to retract the cylinder the entire way? If so, through the schrader valve or some other port? When lifting the jack, how does air escape the cylinder? 

Jgrewe is correct. Weight of car does most of the work and there is a small chamber welded to the main tube that has a Shrader valve. Before using the quickjack, you set the pressure at about 50 psi with the Shrader valve to move it back the last little bit where there is no weight on the jack. The system maintains air pressure for months in my experience.

And thanks for all the info in your other post!

Thanks for the clarification. Because it stores air on the high side of the piston, this is a double-acting design. The piston seal on the low end of the seal keeps the oil out of the high end while the piston seal on the high end keeps air out of the system. Polyurethane seals don't work great with air. I wonder why they used it instead of NBR. I'd be really interested to see what seal is in the head if you end up taking it apart. The PTFE back-up ring damage is especially interesting. I see no way the usage you have given this would cause a piece to be missing. Also, the remnant piece would be in the cylinder somewhere.

A thought, if the failure showed as oil coming out of the Schrader valve, I wonder how much oil bypassed the piston seal and was on the high end of the cylinder? Air and Hydraulic fluid compress at different rates. If a significant amount bypassed, it would raise the 50psi air pressure level on the high side and fight the cylinder extension and put extra pressure on the seals. Did you try draining the fluid out of the top end of the cylinder to see if that effected performance?

sevenracer
sevenracer Reader
3/24/22 5:05 p.m.

In reply to hobiercr :

Not shown in the pics, but the missing piece of the PTFE back-up ring was loose in the cylinder and fell out as the hydraulic oil drained from the dry side. I'd say about 1/2 to a full cup of fluid drained from the dry side.

Interesting point about the volume of hydraulic oil raising the pressure on the dry side. I actually have two failed cylinders. Have just opened up the one. The other is still installed in the jack. I'll try to drain the oil from the shrader valve tonight and see if it changes performance.

Note: The problem encountered with both failures is that the side with the failed cylinder would only start to raise the car and then stop moving while the other side with the good cylinder would behave normally. Oil coming out of the shrader valve was a symptom that I noticed. QuickJack tech support said if oil is in the air side, it's failed and new cylinder needed.

hobiercr
hobiercr UltraDork
3/24/22 5:34 p.m.

In reply to sevenracer :

Look closely at the PTFE ring. If it is a skive-cut split ring you will be able to tell. That is a LOT of fluid in that size cylinder. I bet that was affecting performance. 

When you figure out how to take the piston off we can ID all the parts and build a kit. 

sevenracer
sevenracer Reader
3/24/22 9:24 p.m.

No pics, but no luck unscrewing the piston. Didn't want to mar the surface, so used rubber sheet and vice grips. Wouldn't budge before the rubber slipped on the piston.

Hopefully, tomorrow I can get to a hydraulic shop to see if they know how to disassemble.

PTFE ring appears to have been a complete ring - looks torn at both ends

Then I moved on to the other failed cylinder. First, I connected just the one cylinder and stood on the jack. It lifted about half the way up and then stalled. Next, I Drained the oil from the shrader valve- then promptly managed to spill about half of it. So, estimating from what was on the floor and left in the cup - roughly 4oz total. Finally, re-pressurized with air and re-did the test. It went up almost all the way, but not quite to the upper lock position. So, draining the oil seemed to significantly improve performance - at least with my weight on it.

 

hobiercr
hobiercr UltraDork
3/24/22 10:51 p.m.

Interesting. A failure like that on the backup ring would have to caused by a massive pressure spike on the air end of the cylinder.  I'm interested to hear what the hydraulic shop says.

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