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How to bleed/set up hydraulic/pneumatic cylinder for bender

Squamch

Squamch

Canadian
Joined
May 19, 2020
Member Number
93
Messages
1,514
Loc
republic of Vancouver island
I have a princess auto (canadian Harbour freight) air over hydraulic cylinder on my model 3 bender.
The directions I found online said to pull the fill plug, crack the release 1.5 turns, and connect air for a minute. Then it should be bled. Replace fill plug, tighten release valve, and off ya go.


That's not the case. I did that until no more bubbles were coming out, and it still won't fully extend. I also read mention of needing to overfill it if it's mounted horizontally, which it is. No direction on how exactly to achieve that over filling.


So, do I just need to give it longer on the air to pump the air bubbles out, or what?

This thing has been loaned out for the last couple years to various buddies, and no one will admit to fucking with it, or having any problems.
 
Hmm. Well I'll be of no help but I'd say it'd be a seal let go. I've got the non princess one on my bender and never had an issue with it. Worked straight out of box. It is a vertical bender though but I didn't even bleed it initially.
 
you got it assembled with the air cylinder on the bottom side right?
Pump won't suck oil unless its intake is submerged

it's really just a bottle jack, if you've had one of them apart and can visualize what's going on
 
[486] said:
you got it assembled with the air cylinder on the bottom side right?

Pump won't suck oil unless its intake is submerged
Click to expand...

No. It's on the side. And worked fine like that for 2 years. Now it will only extend 2/3 of the length of the shaft.

Maybe someone backed the release screw too far out and dumped some fluid?

If I wanted to add fluid, what would the process be?
 
just dump in ATF or AW32 or p/s fluid, or whatever thin viscosity oil you've got
the excess will be ejected when you lower the jack completely

have some rags and a catch pan ready
 
So, fill hole at the high point, fully extend the ram, pour oil in, let it hang out for a while for bubbles to percolate out, collapse shaft, put the plug back in, should be good to go?

My fuckery with hydraulics experience is this ram, apart from power steering systems. Not ram assist.
 
nope, ram all the way compressed
fill reservoir (generally with those bottle jack type things you stand it up vertical)
then fiddle with the hydraulics a bit to work the air out
 
Well, I removed it from the bender, filled it, bled it as per directions, and it still won't extend on air past about 40%. Manually pumping it'll go all the way though.
 
Going back to your first post

I got a 500.00 laser handed back to me by a buddy that mysteriously unassembled internals when it came back not working

It was self leveling, other than putting batteries in it I have no idea wtf he was doing in there

but 'weird' things happen on loan for some reason
 
I use one of these air/hydro jacks almost every day in a home made lift in the shop

I have a good 10 years on it, I think I have had to add a little oil once maybe
and it up/downs 20x a day at least

good little cylinders, I might be suspecting a seal at some point
 
I’ve used one once on a buddys bender and half way through the job it blew up spitting air and oil out of it. Foot pedal thing

I had a home brew full Hydraulic old school one I replaced with a newer stronger bender. Full hydraulic. Once you go full hydraulic you’ll never want an air over hydraulic unit. Much better control and feathering with full hydraulic IMO
 
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