AC G won't lift after replacing cylinder packing

Hey guys. You all got me through redoing the brakes on our other G last summer, hopefully there's some help available here. We've got a G with the OEM rear furrowing bar cylinder and bracketing, rigged to lift a homemade bar. This whole rig was built early last summer, which was when the farm got the tractor. The "furrowing" bar is basically a piece of square stock with a couple brackets for sweeps welded on, so the thing can clean up the wheel tracks while it cultivates the bed.

All summer this worked fine--you had to give it some throttle to get it to lift the bar, but it could do it every time. But the cylinder was leaking, just a bit, but enough to make a mess of the ram and I was worried about abrasion and it getting worse. So I ordered the packing material and pulled it all apart, tapped out the old packing, pressed in the new in the same order, and reassembled it all.

It doesn't leak now, but it can't lift the furrowing bar! It tries--you can see it heave--but it doesn't have enough ooomph to do it. Any ideas?

I'm wondering about an air bubble trapped in the lines or cylinder? After hooking the hydraulics back on but before mounting the assembly, I manually compressed the cylinder and, holding it below the level of the tractor, ran it through several extend/retract cycles hoping to burp it. Not sure if that's enough with a 1 way cylinder though. Does it need to be bench bled or something? The tractor's full of fresh hytran as of November or so, and I know the level's good.

Thanks for any pointers--I'm going off to work for another farm this season and I'd really like to leave this little guy in good health.

Luke

sounds like you have a pump problem

Hate to be the bearar of bad news but think about it The only thing that changed was you packed the cyl..Would be that you either reversed the packing or as you put it back down in the barrel it rolled over. Fairly common problem.. Un hook the line that goes to the cylinder at the cylinder an put a guage on it.
Or quick check loosen the line rap a rag around it and see if it sprays pretty strong. My 2 cents worth..

since you say its a one way cylinder,do you have a air relief hole at the end of the cylinder opposite the hose end?
does oil come out that hole. how did you manually compress the cylinder? was the control valve in the down position?
if there is no relief hole then the pump is pushing against compressed air.w/relief,if oil isnt coming out,the packing isnt leaking.
pump problem

"or as you put it back down in the barrel it rolled over"

What does this mean? I"m 99% sure that the discs of the packing (offhand I believe there were 4, but I"m not in the shop at the moment) went in without any sort of twisting. They have a dished and a convex side, but I don"t see how they could end up in there wrong... it"s not like they"re o-rings or something that"s elastic enough to twist about, they"re more like cork.

Lacking any other guidance, I lubed up the new discs (one at a time) with hytran and pushed them in with my thumbs until they seated against the ridge inside. I had the old packing sitting next to me as a guide, after having carefully looked at how the various dished/concaves lined up. Then I lubed up the ram, slipped it in, and reassembled the housing. How can I check if they"ve "rolled"?

The tractor has a front hydraulic lift cylinder which I believe is functioning fine, but I"ll double check that when I"m next at the farm.

I don"t believe the cylinder has any kind of air-relief... And I attempted to bleed it by putting the control lever in "float" (middle position) where I was then able to compress the cylinder by muscle power, then flip the control lever to lift/extend until it was extended... then repeat.

??

Can anyone tell me what the pressure at the pump "ought" to be? The manual gives no help.



The cylinder is (I believe) the original furrowing cylinder for this machine--its externals and internals match perfectly the parts blow up I have. Does that type of ram even have an air hole to bleed in air somewhere? I can"t see where... I understand the concept on a 2way ram that's modified for single action, but I thought with this thing, fluid comes in and pushes the ram out, when the ram returns it displaces the fluid back out the line... so there really isn't an internal place for air to fill and bleed from. Is that wrong? These little G"s are the only 1 way hydraulics I"ve ever worked on, and it"s never been an issue. Does anyone know where such a hole ought to be? I suppose if I had plugged it, or some piece of crud is in there, it could be the culprit here.



There is no oil leaking out the packing. I thought maybe just the stiction of the new, tight packing would put it over the edge so it can"t lift, but if I manually lift up the furrowing bar to help it out (with the lever in the lift/up position), it can"t even hold it up there. Makes me wonder about the air hole issue. So:

1. Where is the air bleed on the OEM rear cylinder?
2. What should pump pressure be?

Thanks!

Luke