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1954 Ford NAA Hydraulic Problem

1

1954-NAA

Member
I have a 1954 Ford NAA. I have had the tractor for 30 years and it was missing the hydraulic pump when I got it. Someone made a plate to cover the place where it bolts to the engine and had cut and brazed the lines at the back of the tractor. I decided to try to get the hydraulics working. I got a used pump and got a set of lines and repaired them. I installed the pump and lines on the tractor but the lift would not raise. I got and watched the hydraulic repair for ford tractors video before taking off the lift cover:

http://www.link_disallowed/VID18D-hydraulic-repair-ford-tractor-video-dvd

I replaced the cam follower pin, changed the rings on the piston, cleaned the control valve, unstuck unload valve and replaced o-ring on the unload valve and I replaced the safety valve with this valve:

http://www.link_disallowed/FDS353-hydraulic-pump-safety-valve-assembly

I replaced the steel ball that goes in before the safety valve.

I put a hydraulic gauge on the pump and can see that I have over 2000 psi pressure when I raise the lift handle, but the lift will not come up. If the raise the lift by hand the pressure will drop when I reach the position that the lift handle is set at. So this part seems to be working correctly, when it reaches the desired level the pressure drops, even though I am raising it by hand.

I am not sure what to try next. I saw something about a check valve and a back pressure valve but I don't even know where they are located on the lift assembly:

http://66.49.166.42/VFTR/hyd.htm

Any way to just plug the safety valve temporarily to see if that is the problem? Any other troubleshooting tricks? Any advice would be greatly appreciated.
 
(quoted from post at 10:37:25 04/20/12) I have a 1954 Ford NAA. I have had the tractor for 30 years and it was missing the hydraulic pump when I got it. Someone made a plate to cover the place where it bolts to the engine and had cut and brazed the lines at the back of the tractor. I decided to try to get the hydraulics working. I got a used pump and got a set of lines and repaired them. I installed the pump and lines on the tractor but the lift would not raise. I got and watched the hydraulic repair for ford tractors video before taking off the lift cover:

http://www.link_disallowed/VID18D-hydraulic-repair-ford-tractor-video-dvd

I replaced the cam follower pin, changed the rings on the piston, cleaned the control valve, unstuck unload valve and replaced o-ring on the unload valve and I replaced the safety valve with this valve:

http://www.link_disallowed/FDS353-hydraulic-pump-safety-valve-assembly

I replaced the steel ball that goes in before the safety valve.

I put a hydraulic gauge on the pump and can see that I have over 2000 psi pressure when I raise the lift handle, but the lift will not come up. If the raise the lift by hand the pressure will drop when I reach the position that the lift handle is set at. So this part seems to be working correctly, when it reaches the desired level the pressure drops, even though I am raising it by hand.

I am not sure what to try next. I saw something about a check valve and a back pressure valve but I don't even know where they are located on the lift assembly:

http://66.49.166.42/VFTR/hyd.htm

Any way to just plug the safety valve temporarily to see if that is the problem? Any other troubleshooting tricks? Any advice would be greatly appreciated.
Click to expand...
f you have 2000psi, you have no reason to try to plug the overpressure safety valve. The check valve consists of the spring loaded ball that you replaced behind the ram cylinder safety valve.
The backpressure valve has a tube attached & is pressed up against the cylinder/valve casting by the acorn nut assy on right side of tractor. Did you remove or move any of the valve bushings while doing your work? It sounds like a blockage between the pump inlet to the check valve bushing, the check valve and the inlet to the ram cylinder.......these are passages in the cylinder/valve casting, in/around valve bushing, through accessory plate on top of lift assy cover.
 
Thank you for the reply.

I did not remove or move any bushings.

Mine has a top plate like this:

https://photos.yesterdaystractors.com/gallery/uptest/a32810.jpg

But no lines connected, both ports are plugged.
 
I should have probably added that when I raise the remote hydraulic lever shown in the picture, the hydraulic gauge registers > 2000 psi. The pressure does not seem to rise when I push it down.
 
(quoted from post at 11:21:12 04/20/12) I should have probably added that when I raise the remote hydraulic lever shown in the picture, the hydraulic gauge registers > 2000 psi. The pressure does not seem to rise when I push it down.
Click to expand...
nowing of that auxilary hyd valve is important. When you use it by raising its lever, you are trying to force pressure out its plugged ports & thus causing pump over pressure valve to operate (2000). When that valve is in neutral position, then it is supposed to allow the pump pressure to reach the 3 point lift system. I have some suspicion that one of the two paths thru that aux valve into the 3 point system may be blocked. I would remove it and use compressed air to verify that they are open & at same time apply air to ram cyl input port to see if lift arms can be made to lift.
 
I removed the auxiliary valve and verified that
the arms lift when I applied compressed air to the
ram cylinder input port. Looking at the auxiliary
valve, the oil path to the ram cylinder input port
does not enter the auxiliary valve, it comes up
from the lift cover and uses the auxiliary valve
to make a "U turn" back to the lift cover ram
cylinder input port.

It seems like the pressure is not making to the
ram cylinder for some reason. The lever and
position of the arms seem to be controlling the
pressure properly, but the pressure is not making
it to the ram input cylinder.
 
(quoted from post at 14:22:20 04/20/12) I removed the auxiliary valve and verified that
the arms lift when I applied compressed air to the
ram cylinder input port. Looking at the auxiliary
valve, the oil path to the ram cylinder input port
does not enter the auxiliary valve, it comes up
from the lift cover and uses the auxiliary valve
to make a "U turn" back to the lift cover ram
cylinder input port.

It seems like the pressure is not making to the
ram cylinder for some reason. The lever and
position of the arms seem to be controlling the
pressure properly, but the pressure is not making
it to the ram input cylinder.
Click to expand...
here is the path that you mention, but there is another path that is input pump pressure & that valve directs it either to the aux ports OR it directs it down into the 3 point system......is that second route thru the valve OK?
hyd_jube_flow_press_input_to_ram.jpg
 
I have this auxiliary valve:

https://photos.yesterdaystractors.com/gallery/uptest/a17106.j
pg

I believe it is designed to direct to the aux
ports AND into the 3 point system.

Please see this discussion:

http://www.ytmag.com/cgi-bin/viewit.cgi?
bd=nboard&th=772490%3E

Thank you.
 
I have 3 NAA's with that remote valve.
I just removed one that was leaking.
while it's off, I'm going to dis-assemble it, and take pics and
pass them here for everyone to look at.
I'm curious what that small T-handle on the right side controls.

Like JMOR is saying, this valve can be used without chaining down the 3-point.
So, in the neutral position, it must pass the oil for the 3-point.
Pulling the handle up or down will block oil to the 3-point and activate
one or the other of your ports.
(otherwise, the 3-point would raise too)
All of my valves are blocked right now, and they act a little different than yours.
Pulling the handle either up or down will pull the motor down and get the relief squealing.
up activates the back port, down the front port if I remember correctly.
(another reason I'm curious about that t-handle...maybe changes it to single-action? up/energize back port, down/gravity down...or maybe just a flow control...we'll see)
Thoughts?


thanks to Leo for the pic
a17106.jpg
 
I would have thought that pulling the handle up OR
down would pull the motor down like yours is doing
would be correct behavior. For some reason mine
only does it when I pull it up. I want to get the
three point lift working first and then I will
work on the auxiliary valve.

I verified that the high pressure does have a
clear path back to the cylinder/valve assembly
when the auxiliary valve is in the neutral
position. [ Still enjoying the taste of hydraulic
oil in my mouth from blowing in ports :) ]

So it looks like I am getting pressure to the
piston/valve assembly and looking at the pressure
gauge things are working correctly when I set the
control lever and then move the lift by hand to
the requested position. Pressure rises and then
drops when I lift to the desired position.

The piston moves when I apply air pressure to the
cylinder port. So it looks to me like I am
getting pressure to the valve assembly, but it
never makes it out of the valve assembly to then
reach the cylinder port.

Three ports on the cylinder/valve assembly where
it meets the lift cover:

1) Pressure In.
2) Pressure Out.
3) Cylinder In.

Looks like I'm clear up to Pressure In. And I am
clear from Pressure Out to Cylinder In. But I am
hung up between Pressure in and Pressure Out.
Even though as I said earlier the pressure gauge
is showing what I think should be happening when I
move the lift handle and manually pick up the lift
arms.

I wonder if I could have some blockage in the
valve assembly? Hydraulics have not worked for
over 30 years. Don't know what is beneath all the
allen head screws on the cylinder/valve assembly.
 
(quoted from post at 20:55:59 04/20/12) I would have thought that pulling the handle up OR
down would pull the motor down like yours is doing
would be correct behavior. For some reason mine
only does it when I pull it up. I want to get the
three point lift working first and then I will
work on the auxiliary valve.

I verified that the high pressure does have a
clear path back to the cylinder/valve assembly
when the auxiliary valve is in the neutral
position. [ Still enjoying the taste of hydraulic
oil in my mouth from blowing in ports :) ]

So it looks like I am getting pressure to the
piston/valve assembly and looking at the pressure
gauge things are working correctly when I set the
control lever and then move the lift by hand to
the requested position. Pressure rises and then
drops when I lift to the desired position.

The piston moves when I apply air pressure to the
cylinder port. So it looks to me like I am
getting pressure to the valve assembly, but it
never makes it out of the valve assembly to then
reach the cylinder port.

Three ports on the cylinder/valve assembly where
it meets the lift cover:

1) Pressure In.
2) Pressure Out.
3) Cylinder In.

Looks like I'm clear up to Pressure In. And I am
clear from Pressure Out to Cylinder In. But I am
hung up between Pressure in and Pressure Out.
Even though as I said earlier the pressure gauge
is showing what I think should be happening when I
move the lift handle and manually pick up the lift
arms.

I wonder if I could have some blockage in the
valve assembly? Hydraulics have not worked for
over 30 years. Don't know what is beneath all the
allen head screws on the cylinder/valve assembly.
Click to expand...
llen head plugs are just plugging holes used in drilling passages during manufacturing.
 
JMOR, thank you for your replies. I have been re-
reading everything and you wrote in one of your
replies:

"It sounds like a blockage between the pump inlet
to the check valve bushing, the check valve and
the inlet to the ram cylinder.......these are
passages in the cylinder/valve casting, in/around
valve bushing, through accessory plate on top of
lift assy cover."

How would I go about checking this? I tried
putting air in the input of the cylinder/valve
assembly but it leaks through, I guess it is not
enough pressure to unseat something.
 
The problem was the check/safety valve. The
FDS353 is supposed to work with an NAA.

http://www.link_disallowed/FDS353-hydraulic-
pump-safety-valve-assembly

I bought a new steel ball from CNH and replaced
that as well as using the aftermarket FDS353. I
don't know if the valve is just wrong or if it is
designed to be used without the steel ball or
what. But, with the steel ball it was too tight
and not letting the check valve release. I took
the plunger and spring off the old check/safety
valve and cut the plunger neck down on the new
check/safety valve and put the old plunger and
spring on the new check/safety valve and it
worked. Lift will now come up with plenty of
power.

But, it is doing the falling and rising thing
about every 2 seconds when I put a load on it. I
will search the forums to see if I can find an
answer to this problem. At least I'm getting
closer.
 
(quoted from post at 01:22:07 04/21/12) The problem was the check/safety valve. The
FDS353 is supposed to work with an NAA.

http://www.link_disallowed/FDS353-hydraulic-
pump-safety-valve-assembly

I bought a new steel ball from CNH and replaced
that as well as using the aftermarket FDS353. I
don't know if the valve is just wrong or if it is
designed to be used without the steel ball or
what. But, with the steel ball it was too tight
and not letting the check valve release. I took
the plunger and spring off the old check/safety
valve and cut the plunger neck down on the new
check/safety valve and put the old plunger and
spring on the new check/safety valve and it
worked. Lift will now come up with plenty of
power.

But, it is doing the falling and rising thing
about every 2 seconds when I put a load on it. I
will search the forums to see if I can find an
answer to this problem. At least I'm getting
closer.
Click to expand...
would be surprised if FDS353 is the correct part. NAA984F is I believe the correct part. Can you try it with your old valve? I suspect that your modified check/ball/spring is your current problem. Ball seat good, ball good, spring compression good? The check valve is likely not holding and thus allowing the cylinder to leak down to the point that the cam follower/position control linkage detects position change and opens control valve to command lift back to original position, then the leak down begins again and the cycle repeats.
 
Mine had a small bypass line run from a fitting on the top front port to a fitting where the t-handle is in the picture. That is why I was not getting any pressure when I pushed the lever down. It was bypassing back into the return system. I put two plain 1/2" caps on the top two ports and plugged the one where the t-handle is in the picture. Now the tractor pulls down when I push the lever down or up. I believe I can now run lines to a remote dual acting cylinder and everything will work fine.
 
(quoted from post at 19:44:16 04/21/12) Mine had a small bypass line run from a fitting on the top front port to a fitting where the t-handle is in the picture. That is why I was not getting any pressure when I pushed the lever down. It was bypassing back into the return system. I put two plain 1/2" caps on the top two ports and plugged the one where the t-handle is in the picture. Now the tractor pulls down when I push the lever down or up. I believe I can now run lines to a remote dual acting cylinder and everything will work fine.
Click to expand...
on't see how that is going to fix this problem you described:"But, it is doing the falling and rising thing
about every 2 seconds when I put a load on it. I
will search the forums to see if I can find an
answer to this problem. At least I'm getting
closer."
 
I bled the system again and raised and lowered the
arms a bunch of times with a load on it. It does
not fall and rise any more. So, I thought all was
well.

I hooked up to my cutter which connects to a draw
bar that I have connected to the 3 point hitch
arms. I adjusted the draw bar to the correct
height and set the stop on the control lever. I
was cutting along when I heard the pto shaft
rubbing on the cutter. The lift had risen on its
own and was binding the pto shaft. I killed the
engine and it finally released and lowered after a
while.

It did it several more times and then I unhooked
the pto shaft to see how high it was trying to
rise. I left the tractor running and observed it
and it did it again. The lift rose all the way to
the top and then released on its own and went down
to the set level. I really need to figure this
out. I am going to tear something up if it keeps
raising on its own and binding the pto shaft.
Thanks in advance for all help.
 
(quoted from post at 13:46:39 04/22/12) I bled the system again and raised and lowered the
arms a bunch of times with a load on it. It does
not fall and rise any more. So, I thought all was
well.

I hooked up to my cutter which connects to a draw
bar that I have connected to the 3 point hitch
arms. I adjusted the draw bar to the correct
height and set the stop on the control lever. I
was cutting along when I heard the pto shaft
rubbing on the cutter. The lift had risen on its
own and was binding the pto shaft. I killed the
engine and it finally released and lowered after a
while.

It did it several more times and then I unhooked
the pto shaft to see how high it was trying to
rise. I left the tractor running and observed it
and it did it again. The lift rose all the way to
the top and then released on its own and went down
to the set level. I really need to figure this
out. I am going to tear something up if it keeps
raising on its own and binding the pto shaft.
Thanks in advance for all help.
Click to expand...
ould be a linkage adjustment problem, but I'm still suspicious of the kludged ram safety & check valve you have in there. You are operating in Position control mode vs Draft control? Explanation of wrong check valve: There is a pressure being applied to the check valve ball/seat in a direction to try to open it and allow flow into the ram cylinder (lift). Normally the pressure required to open that check valve is 115psi, but if your spring/spacing etc. is such that it can be opened at something lower, then the ram can receive input flow even when no lift command is given. The low pressure existing at these times won't lift much load, but with an implement bouncing around back there, the lift arms are holding up varying loads (maybe sometimes no load on a bump) and the ram piston my be inching up a bump at a time so to speak.
 

I am operating in position control mode. The spacing on the spring/plunger/steel ball on the check/safety valve that I kludged together looked to be the same as the old one.

I took it down again to see if I could find anything. The bypass valve was stuck in the open position. Could this have anything to do with it?

I also believe that my relief valve is stuck. I know that probably doesn't have anything to do with this problem. But, when I pull the lever on the dead headed auxiliary valve the pressure pegs my 2000psi gauge. I imagine it is between 2500 and 3000 psi. Shouldn't it release at about 2000 psi? When the lift jammed against the pto shaft I believe the pressure was very great and the relief valve should have released.
 
I don't know why, but these last two posts were
only showing up in modern view. I am posting them
again.

JMOR wrote:

Could be a linkage adjustment problem, but I'm
still suspicious of the kludged ram safety & check
valve you have in there. You are operating in
Position control mode vs Draft control?
Explanation of wrong check valve: There is a
pressure being applied to the check valve
ball/seat in a direction to try to open it and
allow flow into the ram cylinder (lift). Normally
the pressure required to open that check valve is
115psi, but if your spring/spacing etc. is such
that it can be opened at something lower, then the
ram can receive input flow even when no lift
command is given. The low pressure existing at
these times won't lift much load, but with an
implement bouncing around back there, the lift
arms are holding up varying loads (maybe sometimes
no load on a bump) and the ram piston my be
inching up a bump at a time so to speak.

1954-NAA wrote:

I am operating in position control mode. The
spacing on the spring/plunger/steel ball on the
check/safety valve that I kludged together looked
to be the same as the old one.

I took it down again to see if I could find
anything. The bypass valve was stuck in the open
position. Could this have anything to do with it?

I also believe that my relief valve is stuck. I
know that probably doesn't have anything to do
with this problem. But, when I pull the lever on
the dead headed auxiliary valve the pressure pegs
my 2000psi gauge. I imagine it is between 2500 and
3000 psi. Shouldn't it release at about 2000 psi?
When the lift jammed against the pto shaft I
believe the pressure was very great and the relief
valve should have released.
 
(quoted from post at 08:22:17 04/23/12) I don't know why, but these last two posts were
only showing up in modern view. I am posting them
again.

JMOR wrote:

Could be a linkage adjustment problem, but I'm
still suspicious of the kludged ram safety & check
valve you have in there. You are operating in
Position control mode vs Draft control?
Explanation of wrong check valve: There is a
pressure being applied to the check valve
ball/seat in a direction to try to open it and
allow flow into the ram cylinder (lift). Normally
the pressure required to open that check valve is
115psi, but if your spring/spacing etc. is such
that it can be opened at something lower, then the
ram can receive input flow even when no lift
command is given. The low pressure existing at
these times won't lift much load, but with an
implement bouncing around back there, the lift
arms are holding up varying loads (maybe sometimes
no load on a bump) and the ram piston my be
inching up a bump at a time so to speak.

1954-NAA wrote:

I am operating in position control mode. The
spacing on the spring/plunger/steel ball on the
check/safety valve that I kludged together looked
to be the same as the old one.

I took it down again to see if I could find
anything. The bypass valve was stuck in the open
position. Could this have anything to do with it?

I also believe that my relief valve is stuck. I
know that probably doesn't have anything to do
with this problem. But, when I pull the lever on
the dead headed auxiliary valve the pressure pegs
my 2000psi gauge. I imagine it is between 2500 and
3000 psi. Shouldn't it release at about 2000 psi?
When the lift jammed against the pto shaft I
believe the pressure was very great and the relief
valve should have released.
Click to expand...
What are you calling a "bypass valve'? Unloader valve, back pressure valve? As for the primary overpressure valve, 2000 is appropriate.
 
Sorry, I meant to say that the "back pressure" valve was stuck open.

And I an saying that I believe the relief valve may be stuck closed because it is not releasing at 2000psi. Shouldn"t a noise be heard when it releases? I know this is not directly related to the lift problem. But, I am trying to get the entire hydraulic system working properly.
 
(quoted from post at 12:53:04 04/23/12) Sorry, I meant to say that the "back pressure" valve was stuck open.

And I an saying that I believe the relief valve may be stuck closed because it is not releasing at 2000psi. Shouldn"t a noise be heard when it releases? I know this is not directly related to the lift problem. But, I am trying to get the entire hydraulic system working properly.
Click to expand...
ome say that they can hear the relief squeal when relieving.....I probably couldn't, but I might detect a change in engine loading. Of course, one must always consider accuracy of gauge? Why do you say back pressure valve is stuck open? It will be dumping (open) when lift is doing anything besides being raised (open when holding a load, open when lowering). It requires very little pressure to open it....~40psi.
 
Back pressure valve was stuck in the open position
so it was not giving any back pressure to the valve
assembly. Hydraulic oil was flowing out with no
resistance. I took it out and freed it up and
lubricated and now I can open it manually and it
shuts on its own with the spring. Could no back
pressure to the valve assembly have caused my
problem?
 
(quoted from post at 15:24:50 04/23/12) Back pressure valve was stuck in the open position
so it was not giving any back pressure to the valve
assembly. Hydraulic oil was flowing out with no
resistance. I took it out and freed it up and
lubricated and now I can open it manually and it
shuts on its own with the spring. Could no back
pressure to the valve assembly have caused my
problem?
Click to expand...
ith absolutely no back pressure, there would be no pressure to operate the unloader valve & thus no ability to lift. However, any piping/passages/etc. will always provide some restriction & resulting pressure, so maybe that would be enough to operate the unloader valve, but I wouldn't bank on it. As for your problem, ....maybe. I can imagine a situation where a marginal pressure could perhaps move the unloader under some circumstances/speeds/etc. but maybe not under others, so it gets to lift or hold/lower and gets temporarily stuck in one position or another.
 
I ordered a back pressure flat o-ring and a relief valve. When they come in I will install along with the now unstuck back pressure valve. I will let you know how it works. Thank you for the help.
 
(quoted from post at 17:21:21 04/23/12) I ordered a back pressure flat o-ring and a relief valve. When they come in I will install along with the now unstuck back pressure valve. I will let you know how it works. Thank you for the help.
Click to expand...
ou are welcome. My e-mail is always open in Modern View.
 
Mr. JMOR,

My parts came in and I installed. The first thing I did was pulled lever on auxiliary hydraulic valve which is capped. I wanted to see if the relief valve would release at about 2000psi. I did it several times and the pressure was still pegging gauge, I imagine at 2500 to 3000 psi. Finally the pressure dropped to about 250 psi and will not go any higher. I suspect the relief valve may have released. I would have thought it would have reset and been able to be used over and over. The relief valve is not a one time thing is it? Where once it release it is no good? Not sure what to try next. Needless to say I can't do much with 250psi. Thank you.
 
(quoted from post at 15:44:23 04/25/12) Mr. JMOR,

My parts came in and I installed. The first thing I did was pulled lever on auxiliary hydraulic valve which is capped. I wanted to see if the relief valve would release at about 2000psi. I did it several times and the pressure was still pegging gauge, I imagine at 2500 to 3000 psi. Finally the pressure dropped to about 250 psi and will not go any higher. I suspect the relief valve may have released. I would have thought it would have reset and been able to be used over and over. The relief valve is not a one time thing is it? Where once it release it is no good? Not sure what to try next. Needless to say I can't do much with 250psi. Thank you.
Click to expand...
ot a one time affair. It is just a ball held against a seat with a spring. When force overcomes spring it releases & when force (pressure) falls the spring returns ball to seat. Just to be sure we are on same page, "relief valve" brings up a question, since on your tractor there are basically two, one on the ram cylinder/valve assy and another deep in the belly of the tractor hydraulic cavity. Which did you replace?
 

I am talking about the one at the bottom of the hydraulic cavity where the pressure line connects from underneath the tractor.
 

I am talking about the one at the bottom of the hydraulic cavity where the pressure line connects from underneath the tractor.[/quote]K, just checking. There have been cases where a piece of trash gets between ball/seat & won't let it seal. Where is your pressure gauge connected?
 
(quoted from post at 22:55:00 04/25/12) Pressure gauge is connected to the pump.
Click to expand...
ell, if the pressure isn't building when you operate the aux remote valve, then the flow has to be going somewhere & there are not many possibilities. You can eliminate nearly all by removing the aux valve & bolting a gasketed plate over the pressure tube coming up to the top cover where the aux valve attaches. After that is blocked then there is nothing but tubing, gasket between center hyd housing & top cover, and the relief valve.
P.S. "retainer spring clip?"
hyd_NAA_638relief_valve_replacement.jpg
 
Mine does have a retainer spring clip. I made a gasketed plate as you recommended and installed. I took off the right side inspection plate and cranked 'er up. I could see oil flowing down from the top, so I knew it must be the gasket between center hydraulic housing and the top cover. I took it down again and sure enough the gasket had blown to the inside. I have no faith in my relief valve it should have opened at about 2000psi. I was reading 2500 to 3000 psi when I was operating the auxiliary lever. The relief valve should have opened but the gasket blew instead. I guess I will get a new gasket and quit my relief valve testing. It bugs be that it is not releasing properly, but I have to stop this destructive testing and move forward.
 
(quoted from post at 14:43:28 04/26/12) Mine does have a retainer spring clip. I made a gasketed plate as you recommended and installed. I took off the right side inspection plate and cranked 'er up. I could see oil flowing down from the top, so I knew it must be the gasket between center hydraulic housing and the top cover. I took it down again and sure enough the gasket had blown to the inside. I have no faith in my relief valve it should have opened at about 2000psi. I was reading 2500 to 3000 psi when I was operating the auxiliary lever. The relief valve should have opened but the gasket blew instead. I guess I will get a new gasket and quit my relief valve testing. It bugs be that it is not releasing properly, but I have to stop this destructive testing and move forward.
Click to expand...
ounds like you are doing a lot better job trouble shooting than relief valve maker is doing making correct parts! :cry:
 
I got it all back together and unfortunately it is doing the same thing. When holding a load, a cutter hooked to a draw bar between the lift arms in this case, the lift will occasionally rise on its own, reach the maximum height and then release and go down to the original position.

I left the hydraulic pressure gauge on the pump so I could observe. When raising the load the psi is about 750 or so. When the tractor is running and holding the load at the requested height psi seems to vary between 700 to 1000. I wasn't sure if this is normal? When lowering the load, psi drop to near 0.

I am not sure what to do next. I've lost track of the number of times I've taken the lift cover on and off. Any advice greatly appreciated.
 
(quoted from post at 11:06:34 04/27/12) I got it all back together and unfortunately it is doing the same thing. When holding a load, a cutter hooked to a draw bar between the lift arms in this case, the lift will occasionally rise on its own, reach the maximum height and then release and go down to the original position.

I left the hydraulic pressure gauge on the pump so I could observe. When raising the load the psi is about 750 or so. When the tractor is running and holding the load at the requested height psi seems to vary between 700 to 1000. I wasn't sure if this is normal? When lowering the load, psi drop to near 0.

I am not sure what to do next. I've lost track of the number of times I've taken the lift cover on and off. Any advice greatly appreciated.
Click to expand...

"When the tractor is running and holding the load at the requested height psi seems to vary between 700 to 1000. I wasn't sure if this is normal?"
I do not believe this to be normal.
If you raise the load to about 1/2 full height & kill engine, does lift hold or sink? Over what period of time?
 
I raised 1/2 way and killed engine. Lift slowly sank a couple inches at first and then held and I could not see it visibly dropping any more. I watched about twenty minutes and it seemed to be staying in the same position or dropping so slowly it is not noticeable. Thanks.
 
(quoted from post at 16:07:24 04/27/12) I raised 1/2 way and killed engine. Lift slowly sank a couple inches at first and then held and I could not see it visibly dropping any more. I watched about twenty minutes and it seemed to be staying in the same position or dropping so slowly it is not noticeable. Thanks.
Click to expand...

You should not be seeing 700 when no lifting is being commanded. In neutral/hold position & in drop/lower, the pressure should be set by the backpressure valve (very low @ ~ 40). The fact that you see 700 would sound to me like the backpressure valve isn't relieving at the low 40 that it should be. Keep in mind that it only needs 115 to open the check to the lift ram & then up you go. Also, keep in mind that the backpressure valves input is switched by the unloader valve, so if unloader isn't working correctly, then the backpressure valve can't. I don't remember what if any work you have done related to unloader valve? As far as 'when it reached top of lift, it drops back to set position", that is easily explained by the upper limit function, where the ram exits the cylinder, contacting the control arm pin and kicking the arm/valve linkage/control valve/etc. back to stop lift or possibly enough to open lowering circuit.
So, where does this leave things? Suspicious of backpressure valve/unloader valve. When I receive an e-mail from you, if you need some diagrams to help understand operation, then I will send them to you. You may already have on not need.
 
I wanted to follow up on this problem.

I purchase a used lift cylinder assembly and it worked like a charm. Slightly over 0 psi when lift is holding a heavy load in neutral position.

All I can conclude is that the wrong bushing(s) and or valve(s) were in my original assembly. When sliding into the neutral position, it only looks like about a 1/32” to 1/64” opportunity where, in JMOR's drawings, port 4 is blocked and port 5 is not receiving flow from port 3. Maybe years ago someone tried to fix it and put in the wrong parts. That may be why the lift arms were removed and a homemade stationary drawbar was put on the tractor. Then I guess someone took the pump and lines off because they weren’t being used.

I was not of a mind to take apart the new assembly and look for differences, but I did notice that the three bolt plate that holds in the control valve looked different on the new one. It also seemed like a little more control valve length was sticking out when fully extended, but it could be my imagination. The tractor can now go back to full duty instead of being reduced to fixed drawbar only work. I cut a couple of acres and I believer this has cured the “lifting on its own” problem too.
 
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