9N Lift arms will not lower

[lucky51]

Greetings,
This lift use to work just fine until one day I raised the disc I had attached to it and it wouldn't go down. So far I have drained and flushed out the hydraulic fluid. I have checked the movement of the valve and fork which are connected and move the valve in and out about an inch or so. I have removed the upper lift cover and peered into the case for anything obvious.
For an experiment I blew into the pressure tube on the assumption that the exhaust port may be plugged solid. I removed the valve from the pump to be sure it wasn't the cause of the plug. When I applied 125 pounds of air pressure nothing happened. There were no bubbles or noise.
Since the lift works going up I can assume the the line from the inlet port of the pump to the cylinder is clear, and that the plug, if there is one, is at the exhaust port itself.
Does this make sense to anyone or am I missing something? Has anyone tried to put pressure on the line to clear a clog? Is there another cause for the lift not lowering?
Thanks in advance,
Lucky51

 

[Jerry/MT]

Greetings,
This lift use to work just fine until one day I raised the disc I had attached to it and it wouldn't go down. So far I have drained and flushed out the hydraulic fluid. I have checked the movement of the valve and fork which are connected and move the valve in and out about an inch or so. I have removed the upper lift cover and peered into the case for anything obvious.
For an experiment I blew into the pressure tube on the assumption that the exhaust port may be plugged solid. I removed the valve from the pump to be sure it wasn't the cause of the plug. When I applied 125 pounds of air pressure nothing happened. There were no bubbles or noise.
Since the lift works going up I can assume the the line from the inlet port of the pump to the cylinder is clear, and that the plug, if there is one, is at the exhaust port itself.
Does this make sense to anyone or am I missing something? Has anyone tried to put pressure on the line to clear a clog? Is there another cause for the lift not lowering?
Thanks in advance,
Lucky51

Are you saying that the lift stays up with an implement even when the control valve is moved back to the drop position? If that's the case, the piston maybe siezed in the lift cylinder or the exhaust port is blocked but I never never heard of that condition before. I think anything is possible with these old machines but that would be a rare condition, because the pressure is relatively high when the exhaust port is uncovered.

If you manually move the control valve and the lift drops then I'd say you had a sticky control valve. There's probably some crud that's causing it to stick. The control valve should slide back and forth about an inch total without much force being applied.
Looking through the side access opening, is the control fork moving back and forth smoothly when the lift lever moves up and down (forward when the lever raises and rearward when the lever is pushed down)?

Where did you apply the compressed air? I'm not familiar with the "pressure tube" you are refering to. There is some pump outlet ports on the corner of pump base and the lift cover as I recall. The pump has check valves on it so I don't see how you can blow back through it. However you should be able to blow back when the control valve is back in the lower position because the exhaust port is uncovered if the valve is functioning properly. When you try to blow compressed air in what you call the "pressure tube", IF it is in fact the pressure supply line and the control valve is in the rear position, air should flow through to the reservior.

 

[lucky51]

hi jerry,
What i meant to say was that the lift would raise with the disc attached to the tractor but it will not lower on demand. If you allow the tractor to set for several minutes it will lower on its own very slowly. The piston is not stuck or it wouldn't raise.
I called the the fluid line going from the pump to the cylinder the "pressure tube" due to the lack of the proper term for it.
When I applied air pressure to that line I already had the valve removed completely and sitting on my bench.
If by what you are saying that there are check valves within the pump then that would explain why I don't see or hear bubbles when the air is applied.

 

[Jerry/MT]

hi jerry,
What i meant to say was that the lift would raise with the disc attached to the tractor but it will not lower on demand. If you allow the tractor to set for several minutes it will lower on its own very slowly. The piston is not stuck or it wouldn't raise.
I called the the fluid line going from the pump to the cylinder the "pressure tube" due to the lack of the proper term for it.
When I applied air pressure to that line I already had the valve removed completely and sitting on my bench.
If by what you are saying that there are check valves within the pump then that would explain why I don't see or hear bubbles when the air is applied.

if yu have the valve out, are there any marks on it or any varnish, crud etc. that would impair it's motion. Feel around the bore of the valve in the pump housing for roughness, etc. Reintsall it and then check it with pressure.

What I meant was that IF the valve was in the lower position, i.e. full back, the only place the air could come out was the exhaust port on the control valve. It would not come out o the pump beause its woeold be closedIf the valve was in the raised position (full forward)or the neutral position, then the air wouldn't come out because the exhaust port would be covered. So if you want to blow air in the pressure port to see if the exhaust port is clear, you must have the control valve fully back. This means the lift lever must be fully down. I think the valves in the pump are spring loaded closed when the pump is off so I you wouldn't hear the air in the pump but that's not where your problem is. It's in the control valve I believe. So recheck it with compressed air but first make sure that the lift lever is full down and make sure the control valve moves full back when the lever is full down. I hope this makes sense to you.

 

[lucky51]

Ok, I'll install the valve and try it again. I have the lift cover off so I'll have to hold the valve in place while my son applies the air pressure. I was assuming that if the valve was totally removed from the pump then the exhaust port would be open.
Since this problem happened suddenly I'm hoping that it's just plugged. Gotta lot of
plowing and discing to do really soon. lol

 

[Briana03]

WELCOME to TBN

I moved your thread to the Ford Vintage Tractors Forum.

 

[Soundguy]

my bet is it's either not moving freely ( probably not the case ) or plugged exhaust .

soundguy