Jubilee/NAA Center Case relief valve questions

I have a Jubilee/NAA with some hydraulic issues im trying to fix. Already rebuilt the piston pump, cleaned the lines, freed up the lift cylinder and new gaskets, freed up the back pressure valve and still have no lift even though when I pull the plug off the pump oil comes pouring out. I took the side cover off and looked for it to rain down from the safety valve but it's not happening, and I dont even see the fluid churning for that matter which is odd. I am curious what the relief valve in the bottom of the center casing does, how it functions and what the symptoms would be if it were stuck open or shut.
 
Did you check the unloading valve?? Good chance it is stuck and needs to be pulled out and a new o-ring put on it
 

Done that already. I tried to punch out the other smaller plug but it wouldnt budge so I assumed it was pressed in instead.
 

So I literally just plugged off the back pressure port on the cylinder itself that goes to the acorn nut and reinstalled the cover and still no lift.
 
(quoted from post at 15:57:07 01/06/23)
So I literally just plugged off the back pressure port on the cylinder itself that goes to the acorn nut and reinstalled the cover and still no lift.
dzuoRAJ.jpg

as seen in drawing, both bypass (also called unloader) valve and control valve must be in positions shown to achieve lift. The safety valve in bottom of cavity is pump overpressure valve and the one up on cylinder is ram safety valve,
1rcqVEN.jpg
 
So im not sure what this means, but I got desperate and just stuck my hand in the cavity and felt for oil while a partner cranked the engine over (with no spark plugs) and despite my plug on the port ive discovered that fluid is pouring out of that port around the rubber button seat and my cap and the acorn bolt, that would be part of why im not building pressure. Taking off the remote cover and blowing air in the hole does make the arms jump but for some reason the tractor cant do it itself, probably because the air shot is more direct.

This post was edited by ChairDancer on 01/06/2023 at 01:56 pm.
 
(quoted from post at 17:20:03 01/06/23) So im not sure what this means, but I got desperate and just stuck my hand in the cavity and felt for oil while a partner cranked the engine over (with no spark plugs) and despite my plug on the port ive discovered that fluid is pouring out of that port around the rubber button seat and my cap and the acorn bolt, that would be part of why im not building pressure. Taking off the remote cover and blowing air in the hole does make the arms jump but for some reason the tractor cant do it itself, probably because the air shot is more direct.

This post was edited by ChairDancer on 01/06/2023 at 01:56 pm.
hat it means is that the bypass/unloader valve is in the wrong position for LIFT. It is in the position for Neutral/hold and Lower. Red is your air path and yellow is the pump dumping out the backpressure valve port. The backpressure valve allows dumping excess while maintaining a low pressure ~ 40psi that is necessary to move the bypass/unloader valve into the lift position.
2N2GJjY.jpg
 
Why isnt my bypass/unloader valve moving then when I move the handle up and down for the control valve? Or does it have to be positioned manually during the repair of it? Maybe I did something wrong and it's stuck in one spot and I dont realize it?

This post was edited by ChairDancer on 01/06/2023 at 03:07 pm.
 
(quoted from post at 19:02:38 01/06/23) Why isnt my bypass/unloader valve moving then when I move the handle up and down for the control valve? Or does it have to be positioned manually during the repair of it? Maybe I did something wrong and it's stuck in one spot and I dont realize it?

This post was edited by ChairDancer on 01/06/2023 at 03:07 pm.
ould be stuck....I can't tell from this distance. Is your back-pressure valve bypassing & maintaining back-pressure?
 
At this point im not ruling out a defective back pressure valve still so my plan is to delete the old one and have the port be tapped and put in an elbow and custom blow off while putting a bung in the casing for the old acorn nut. I read that the system needs 2000 psi to work but what pressure does the back pressure valve need to be at to finally open so I can get the right blow off, or is it the 2000?

This post was edited by ChairDancer on 01/07/2023 at 05:57 am.
 
(quoted from post at 08:49:12 01/07/23) At this point im not ruling out a defective back pressure valve still so my plan is to delete the old one and have the port be tapped and put in an elbow and custom blow off while putting a bung in the casing for the old acorn nut. I read that the system needs 2000 psi to work but what pressure does the back pressure valve need to be at to finally open so I can get the right blow off, or is it the 2000?

This post was edited by ChairDancer on 01/07/2023 at 05:57 am.
don't know the exact pressure & have never seen a number in any manual, but along life's way I picked up 40psi somewhere. Feel the spring and you can easily tell that it is NOT a high pressure. Are you sure that the threaded sleeve is pressing the back pressure valve firmly against the sealing washer?
f1bGCsq.jpg
 
As far as I can reasonably crank it without breaking something. It has to stick out some tiny bit for the acorn nut to grab but also not a million miles, so I have a small crescent wrench that fits perfect in the slot tabs and I use that to wind it in until it snugs as hard as I dare.

As far as the spring I thought it felt pretty weak compared to what I would imagine it would take to run the system, a simple screwdriver and some force moved it surprisingly well once I freed it up, since it was originally stuck open. So I tapped on it gently back and forth and it came lose.

This post was edited by ChairDancer on 01/07/2023 at 07:15 am.
 

I assume you're talking about the flat o ring that pops into the nickel sized hole in the side of the cylinder housing? If so I initially tried it with a brand new one and still no lift, it wasn't until I blocked it off with a plastic cap and then stuck my hand in that I discovered it was still leaking around it.
 
(quoted from post at 12:44:22 01/07/23)
I assume you're talking about the flat o ring that pops into the nickel sized hole in the side of the cylinder housing? If so I initially tried it with a brand new one and still no lift, it wasn't until I blocked it off with a plastic cap and then stuck my hand in that I discovered it was still leaking around it.
f trying to use O-ring, that may be your problem, as it is a gasket that looks more like a garden hose washer than an O-ring. PN NAA-989
 
(quoted from post at 12:10:25 01/07/23) Confirm - back pressure approx 40-45 PSI

<IMG SRC=https://i.postimg.cc/8cf305bX/Unload-Pressure.jpg>
hanks Andy. It is in fact in the FO-19. If I saw it sometime, I guess I forgot or overlooked it.
 
I suppose as you guys say fluid shouldn't be making it down there to begin with whether i've attempted to block it off or not. So ill have to open the valve area again and see if the unloading one is still stuck on an old grime ridge or how freely it moves by hand. There could also be a plugged passage as it looks like the control and unloader can talk to each other from your diagram.
 
Down where? What does this mean? " as you guys say fluid shouldn't be making it down there to begin with "
also, when you attempted to block the port that back pressure valve is normally attached to, you were forcing the pump into a dead-head situation where the 2000 PSI over pressure valve had to open in order for the pump outlet to have anywhere to relieve pressure. However, if all that did take place, the ram should have seen that pressure and lifted the arms. Once that port was blocked, there is nothing obstructing flow from pump to ram except the check valve and it would normally open with pressure applied.

This post was edited by JMOR on 01/07/2023 at 03:09 pm.
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top