NAA unloader valve

Mrzspa

Member
I am working on an NAA 600 lift cover. just bought this tractor. lift did not work but pump does. I pulled lift cover and found the unloader valve venting oil pressure back into the oil reservoir/ trans housing. I reworked with CNH correct gaskets and orings. unloader valve moves freely, but as soon as I put air pressure to the lift cover to bench test the unit the unloader valve changes possission and again dumps the pressure. I went to the local dealer to visit with shop tech. they think the book is wrong and unloader valve and valve body are in backwards??? any thoughts, has anyone else experienced this issue.
 
Do you have a NAA or 600? The lift covers are different. NAA has external back pressure valve. 600 has internal back pressure valve.
 
There are a number of folks here that can tell you which way it belongs, but first we need to know what tractor, and a really good description of how it is 'backwards', preferably quality pictures.
 
I know the lift cover say NAA on it inside. looking at the repair manual, it appears to have the updated unloader valve. By comparing photos on the internet it is NAA. I can not figure why the unloader quickly dumps the moment pressure gets to it.
 
NAA tractor, the ports in the machined valve body had pieces of red silicone gasket material lodged through out the entire cast cylinder body. I pressed out the machined valve bodies. I was very careful to see that they were replaced in the same port indexing as they were before. This lift did not work when I got the tractor. I suspect that someone took this apart some time back, Hence the red silicone spread generously around the case.
I am assuming it was reassembled incorrectly by the red silicone bandit. It is the quick dumping of pressure that I need to correct.
 
The unloader & backpressure valves work together to dump the pump output at all times when the Lift command is not present, i.e., when in Hold & Lower. So, maybe you are seeing normal?
 
ok bear with me, I have lift cover clamped in my vise. I put air pressure to the port on the lift cover and snap the unloader valve starts releasing the air pressure. don't I need this to stop releasing pressure so piston can move forward to operate the lift arms?
 
(quoted from post at 01:01:49 12/04/15) ok bear with me, I have lift cover clamped in my vise. I put air pressure to the port on the lift cover and snap the unloader valve starts releasing the air pressure. don't I need this to stop releasing pressure so piston can move forward to operate the lift arms?
t can only stop releasing pressure IF the control valve is moved to the Lift position. At all other times, it will release pressure.
 
ok, understood. so what apparently is not happening is the control lever is set to lift possession. What is not happening is, the unloader is not stopping to unload the pressure, so no lift is occurring.
 
OK, this is assuming that you have NAA & not Hundred series (which I am not sure of). Look at this 'raising' cartoon....when the control valve is in Lift position shown, it allows pump pressure to be applied to BOTH 5 and 6 ports, which will move the unloader spool (called bypass valve in this cartoon)to the left, which blocks the dumping of pump via the backpressure valve to the sump.
In the "Hold/Neutral" cartoon, you can see that control valve is positioned so as to apply pressure only to 6, thus moving unloader to right & allowing pump to dump thru unloader (7 & 8) & backpressure valves to the sump.


 
(quoted from post at 01:30:22 12/04/15) OK, this is assuming that you have NAA & not Hundred series (which I am not sure of). Look at this 'raising' cartoon....when the control valve is in Lift position shown, it allows pump pressure to be applied to BOTH 5 and 6 ports, which will move the unloader spool (called bypass valve in this cartoon)to the left, which blocks the dumping of pump via the backpressure valve to the sump.
In the "Hold/Neutral" cartoon, you can see that control valve is positioned so as to apply pressure only to 6, thus moving unloader to right & allowing pump to dump thru unloader (7 & 8) & backpressure valves to the sump.


lso, again assuming NAA, the back pressure valve must be in place during your bench testing, as it's relief pressure in the pressure which operates the unloader valve.
 
(quoted from post at 14:48:16 12/05/15)
Thank you for helping me and being so patient,where is the back pressure valve located?
F it is an NAA, it is captured between the side of the hyd compartment/sump and the ram/valve casting. In the first picture, it is the silver piece with tube running down to the rear & against the right wall.
Here, it is stand alone.

Here, is the circular area of the ram/valve body casting that it connects to by a rubber-like washer & compression.
 
It is NAA, I rechecked # NAA82027
The pictures are the same. The port on the ram/valve body shown is where the leakage is coming out of.

So, on the cartoon illustration, as soon as I put air pressure to the pressure port of the lift cover, the bypass valve dumps the air out that port. Am I missing the bypass valve? Your picture of the ram/valve body looks exactly like mine. There is no attached back pressure valve outside of that open port. except there is the tube as shown attached to the side of the sump as shown in your photo. if that is the back pressure valve? What connects the two? you mention a rubber like washer and compression. so the cover must be back on to operate correctly? no bench test?
Also, it appears that in your picture the tube is attached to the wall with a clamp. this one does not have a clamp. it swings free.
 
(quoted from post at 20:12:23 12/06/15) It is NAA, I rechecked # NAA82027
The pictures are the same. The port on the ram/valve body shown is where the leakage is coming out of.

So, on the cartoon illustration, as soon as I put air pressure to the pressure port of the lift cover, the bypass valve dumps the air out that port. Am I missing the bypass valve? Your picture of the ram/valve body looks exactly like mine. There is no attached back pressure valve outside of that open port. except there is the tube as shown attached to the side of the sump as shown in your photo. if that is the back pressure valve? What connects the two? you mention a rubber like washer and compression. so the cover must be back on to operate correctly? no bench test?
Also, it appears that in your picture the tube is attached to the wall with a clamp. this one does not have a clamp. it swings free.
hat is the backpressure valve. Washer might be stuck to it or the valve body or might have fallen down into the sump when assy removed. Cover back on and washer in place & backpressure valve seated to washer & valve body OR, on the bench, you might be able to attach it with a clamp, maybe a c-clamp or even a large hose clamp. It relieves at about 40 pounds, so even a strong hand will probably keep it in position.
There is an Acorn nut on outside of hyd sump that holds it in place & presses it against the valve body & washer.
 

Wow you are right! I see what was missing now! so I picked up the flat o-ring rubber washer from FNH, but I can blow air through the back pressure valve from any of the three sides with just mouth pressure. so do you recommend replace, rebuild? let me know.

Thank you so much.
 
(quoted from post at 17:29:08 12/08/15)
Wow you are right! I see what was missing now! so I picked up the flat o-ring rubber washer from FNH, but I can blow air through the back pressure valve from any of the three sides with just mouth pressure. so do you recommend replace, rebuild? let me know.

Thank you so much.
t is a light spring, so it does not take a lot of pressure to unseat it. As for your being able to get flow via 3 instead of 2 openings, I do not have an absolute for you on that question. It MAY be that without the threaded sleeve & acorn nut attached that flow can come out the left side of my cartoon.......I just don't know for sure. I doubt that part is rebuild-able.
 

I took the whole valve body apart to clean out all the chunks of silicone gasket sealer that the previous mechanic had apparently left in the sump and now was lodged in all the porting and valve bodies.
that is all done and reassembled.

Do you have a drawing or cartoon that shows behind which threaded plug the 1/4 inch spring and steel ball go?
 
(quoted from post at 18:08:17 12/27/15)
I took the whole valve body apart to clean out all the chunks of silicone gasket sealer that the previous mechanic had apparently left in the sump and now was lodged in all the porting and valve bodies.
that is all done and reassembled.

Do you have a drawing or cartoon that shows behind which threaded plug the 1/4 inch spring and steel ball go?
ot around any dwgs or manuals now, but sounds like check valve parts that go in hole behind/before ram cyl relief valve
 
ok thanks I will look. I just want to make sure this is right. If you have a picture that would be great.
 
Just checking in to see if you able to find a drawing that shows exactly which threaded plug the steel ball and spring are to be located behind, on the ram cylinder?

Your help and expertise are greatly appreciated.
 
(quoted from post at 18:40:58 01/05/16) Just checking in to see if you able to find a drawing that shows exactly which threaded plug the steel ball and spring are to be located behind, on the ram cylinder?

Your help and expertise are greatly appreciated.
n this first photo, you see the Ram Cylinder Safety Valve marked. Behind it is a spring and a ball. The spring, ball and the part that ball seats against is the check valve.
In the second photo (manual drawing), the Ram Cylinder Safety Valve is incorrectly marked as Check Valve, but you can see the spring & ball behind it.


 

When I washed out the valve body/cylinder after pulling all the threaded plugs. In the screen at the bottom of the parts pan, was a 1/4 inch ball and a small(1/2 long spring. the reason I washed out the valve ports is because there was gasket debris I assume from the previous owners carless gasket scrapings.
I don't know from which port these came??? can you help me?

Thanks
 
(quoted from post at 22:12:11 01/05/16)
When I washed out the valve body/cylinder after pulling all the threaded plugs. In the screen at the bottom of the parts pan, was a 1/4 inch ball and a small(1/2 long spring. the reason I washed out the valve ports is because there was gasket debris I assume from the previous owners carless gasket scrapings.
I don't know from which port these came??? can you help me?

Thanks
o you not think that they are the check valve parts that I pictured?
 

The check valve pictured has a 3/8 ball and spring. this is not from that, it is smaller. 1/4 inch ball and 1/4 x 1/2 inch long spring. it is definitely a check valve apparatus.no other parts just spring and ball. This is not a part of the check valve you have shown. that is a complete unit with spring and ball.
 
(quoted from post at 00:58:27 01/06/16)
one of the pictures attached shows #480 check valve of fig. FO260
K, show me a picture of what you are talking about.
 
I don't know how to attach a photo to this forum,
do you have a regular email and I can send it right away.
 
YT, safe-mail assistant address is always open for me in Modern View, but you apparently use Classic View, so I opened that Safe-Mail address here, too.
 

I sent you my info on safe message. I am a new be at computers, bear with me. . . I have photos, but need an address to send it to. I have no clue how to attach a photo here.
 
(quoted from post at 10:35:20 01/06/16)
I sent you my info on safe message. I am a new be at computers, bear with me. . . I have photos, but need an address to send it to. I have no clue how to attach a photo here.
31603.jpg
31604.jpg
 
in the picture above the check valve #480 is that possibly where the ball and spring came from?
 
(quoted from post at 17:11:14 01/06/16) in the picture above the check valve #480 is that possibly where the ball and spring came from?
hat is exactly the place that I suggested earlier, but then you responded, with "The check valve pictured has a 3/8 ball and spring. this is not from that, it is smaller. 1/4 inch ball and 1/4 x 1/2 inch long spring. it is definitely a check valve apparatus.no other parts just spring and ball. This is not a part of the check valve you have shown. that is a complete unit with spring and ball."....so clearly, I do not understand what you are telling or asking at this point.
 
I am sorry that I was not clear.
In my first picture above,(FO260) In the top left hand corner, there is ram cylinder safety valve. (in red ink, #NAA984F)
I have that valve, it is complete and operational.
just below red ink, (#955) the back pressure valve.
I have that Back pressure valve. It is ok and it is complete.
Below that in red ink (#480) check valve This looks like the Ball and spring I have as is shown in the other picture I posted above laying next to the tape measure.
My question is; Can you tell me, behind which threaded plug this check valve (ball and spring) belongs?
When I removed the treaded plugs and washed the ram valve body out, this Ball and spring were flushed out of one of the ports along with gasket debris. I do not know which one.
 
(quoted from post at 21:30:59 01/06/16) I am sorry that I was not clear.
In my first picture above,(FO260) In the top left hand corner, there is ram cylinder safety valve. (in red ink, #NAA984F)
I have that valve, it is complete and operational.
just below red ink, (#955) the back pressure valve.
I have that Back pressure valve. It is ok and it is complete.
Below that in red ink (#480) check valve This looks like the Ball and spring I have as is shown in the other picture I posted above laying next to the tape measure.
My question is; Can you tell me, behind which threaded plug this check valve (ball and spring) belongs?
When I removed the treaded plugs and washed the ram valve body out, this Ball and spring were flushed out of one of the ports along with gasket debris. I do not know which one.
OK. I'm beginning to see the problem here. From the outset, there was some question as to whether you have an NAA or a 600 series tractor. Somewhere along the way it was decided that you have the NAA. The FO-260 is for a hundred series, not the NAA, so that explains a lot! I don't know where you got that. It is in my photobucket account, but is mislabeled. I would not have called it as NAA in any post that I made.
Here are lift covers for hundred series & for NAA. Now, once & for all, which do you have?
Forget about the diverter valve/hose/etc., just look at the circled plug....have it or not?
next is NAA:
look at the accessory plate cover at upper right....does yours look like this?
 
(quoted from post at 17:14:55 01/06/16)
(quoted from post at 17:11:14 01/06/16) in the picture above the check valve #480 is that possibly where the ball and spring came from?
hat is exactly the place that I suggested earlier, but then you responded, with "The check valve pictured has a 3/8 ball and spring. this is not from that, it is smaller. 1/4 inch ball and 1/4 x 1/2 inch long spring. it is definitely a check valve apparatus.no other parts just spring and ball. This is not a part of the check valve you have shown. that is a complete unit with spring and ball."....so clearly, I do not understand what you are telling or asking at this point.
 
(quoted from post at 00:34:59 01/07/16)
(quoted from post at 21:30:59 01/06/16) I am sorry that I was not clear.
In my first picture above,(FO260) In the top left hand corner, there is ram cylinder safety valve. (in red ink, #NAA984F)
I have that valve, it is complete and operational.
just below red ink, (#955) the back pressure valve.
I have that Back pressure valve. It is ok and it is complete.
Below that in red ink (#480) check valve This looks like the Ball and spring I have as is shown in the other picture I posted above laying next to the tape measure.
My question is; Can you tell me, behind which threaded plug this check valve (ball and spring) belongs?
When I removed the treaded plugs and washed the ram valve body out, this Ball and spring were flushed out of one of the ports along with gasket debris. I do not know which one.
OK. I'm beginning to see the problem here. From the outset, there was some question as to whether you have an NAA or a 600 series tractor. Somewhere along the way it was decided that you have the NAA. The FO-260 is for a hundred series, not the NAA, so that explains a lot! I don't know where you got that. It is in my photobucket account, but is mislabeled. I would not have called it as NAA in any post that I made.
Here are lift covers for hundred series & for NAA. Now, once & for all, which do you have?
Forget about the diverter valve/hose/etc., just look at the circled plug....have it or not?
next is NAA:
look at the accessory plate cover at upper right....does yours look like this?
o, which of these two do you have?
 
(quoted from post at 10:29:45 01/07/16) OK, I may have finally figured out where the spring & ball go. Look here:
Thank you for you patience with me, I think it is not that,
I did not disassemble that part of the lift cover. I only removed the valve body/cylinder. The detent for draft lever was not removed. This came out of the valve body/cylinder its self.
 
(quoted from post at 15:38:14 01/07/16)
(quoted from post at 10:29:45 01/07/16) OK, I may have finally figured out where the spring & ball go. Look here:
Thank you for you patience with me, I think it is not that,
I did not disassemble that part of the lift cover. I only removed the valve body/cylinder. The detent for draft lever was not removed. This came out of the valve body/cylinder its self.
s far as I have ever seen/known, there is no place for that small spring & ball in the valve body/cylinder assembly of the NAA. Only similar is the check valve which you have determined that is is too small to fit. I expect that someone along the path of the last 60 years dropped those parts in there, perhaps from having both hyd & transmission open at same time....no one here now knows.
 
I realize this post is over a year old but as I was researching answers for my NAA hydraulic lift problems I came across this article. It was interesting to me because I am having the same problem.
Anyways, I think I found the little spring and small ball Mrzspa found.
I think it came out of the "Check Valve".
My check valve has a cap on the end towards the front of the tractor that has fine threads to keep it on. Under that cap is a spring with a ball. On the other end is the bigger spring that pushes against the check ball.
What do you think?

I've been reading as much as possible on this site. I even ordered 2 manuals yesterday from your website.
I am wondering how to get the unloader valve out.
I think mine is stuck and will not let my hydraulics lift anything heavy. I will lift me but nothing else.
I read where someone said he used some washers and screw but I don't understand.
On the side of the cylinder cast with the baffle there is a plug that is about the size of a nickle. It is held in place with the thick triangular plate and 3 bolts. I was thinking the undloader vavle is in this port. When I removed the other side plate I could see the spool inside the port but could not get it out. As if it was stuck and what might be causing me my problems.
Any thoughts?
 
(quoted from post at 07:08:41 06/15/17) I realize this post is over a year old but as I was researching answers for my NAA hydraulic lift problems I came across this article. It was interesting to me because I am having the same problem.
Anyways, I think I found the little spring and small ball Mrzspa found.
I think it came out of the "Check Valve".
My check valve has a cap on the end towards the front of the tractor that has fine threads to keep it on. Under that cap is a spring with a ball. On the other end is the bigger spring that pushes against the check ball.
What do you think?

I've been reading as much as possible on this site. I even ordered 2 manuals yesterday from your website.
I am wondering how to get the unloader valve out.
I think mine is stuck and will not let my hydraulics lift anything heavy. I will lift me but nothing else.
I read where someone said he used some washers and screw but I don't understand.
On the side of the cylinder cast with the baffle there is a plug that is about the size of a nickle. It is held in place with the thick triangular plate and 3 bolts. I was thinking the undloader vavle is in this port. When I removed the other side plate I could see the spool inside the port but could not get it out. As if it was stuck and what might be causing me my problems.
Any thoughts?
Under that cap"....that is ram cylinder safety relief valve & the cap usually has a spot of solder to prevent tampering of the set pressure. Maybe his ball/spring came from there, but I have never seen inside the cap?
The "washers & screw" make shift puller applies to hundred series tractors, not the NAA. Some people generalize & apparently think a 'tractor is a tractor', so if something applies to one, it must apply to all! Just use a small punch and tap on the center of the unloader valve spool and you will be able to push the spool and nickel size plate out the other side.

 

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