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Ford 8n Hydraulics seems to try and coorect itself

D

deerhunter#1

New User
I am new to Tractors. I purchased a Ford 8n and noticed the hydraulics would drift down and would not lift all the way when I had a load. I replaced the piston, safety valve and hydraulic fluid and it no longer drifts down. However, when I move the touch control lever to the top to raise the hydraulics with a load it will raid to the top then go half way down without me moving the touch control. It seem like it is trying to correct itself. Any help would be great. Thank you
 
(quoted from post at 10:18:33 02/06/16) I am new to Tractors. I purchased a Ford 8n and noticed the hydraulics would drift down and would not lift all the way when I had a load. I replaced the piston, safety valve and hydraulic fluid and it no longer drifts down. However, when I move the touch control lever to the top to raise the hydraulics with a load it will raid to the top then go half way down without me moving the touch control. It seem like it is trying to correct itself. Any help would be great. Thank you
Click to expand...

You have an 8N which has two different modes of operation selected by the lever under the right side of the operators seat. Draft mode is used for ground engaging implements like a plow and it automagically adjusts the implement height to maintain an even pull on the tractor as soil conditions change. Position control is used for things like mowers and maintains a set implement height regardless of changes in ground level. Both modes utilize internal mechanical feedback linkages to sense and correct for the changes. You need to read and understand the manual instructions on when and how to use the two modes and if they are not working properly those linkages probably need to be adjusted as described in teh shop manual.

TOH
 
Thanks TOH for the quick reply. Ok, I went to the owners manual and found the position control lever. I installed a back blade and tried the position control lever in both the horizontal and vertical position. When I move the hydraulic control lever to the top to raise the blade - the blade goes up then down about halfway even though I did not touch the hydraulic control lever which was left up at the top. It perform the same with the position control lever in both the horizontal or vertical position.
 
(quoted from post at 14:29:18 02/06/16) Thanks TOH for the quick reply. Ok, I went to the owners manual and found the position control lever. I installed a back blade and tried the position control lever in both the horizontal and vertical position. When I move the hydraulic control lever to the top to raise the blade - the blade goes up then down about halfway even though I did not touch the hydraulic control lever which was left up at the top. It perform the same with the position control lever in both the horizontal or vertical position.
Click to expand...

The lift control lever has a friction disc that is supposed to keep it at whatever position you place it. Start by checking that. If that is OK the internal linkage is likely worn and/or out of adjustment.

All of that is documented in the shop manual.

TOH
 
The lift linkage may be way out of adjustment.

The 8N has a safety feature where when the lift reaches the top of it's travel a big dowel that sticks out over the opening in the ram cylinder is
pushed when the piston comes part way out of it's bore and pulls the control valve out of it's bushing. This is what prevents the lift from being over
pressurized when the lift goes to it's maximum height.

Pretty ingenious!

Zane
 
Still struggling with hydraulics and trying to learn. While testing hydraulics today I noticed when the Position(drawbar)control lever is in the horizontal position and I apply pressure or a down force on the lever the back blade will lift all the way up and stay up. Once I release the pressure of pushing down on lever the back blade starts to drop. Also after I replaced the piston with the new setup with neoprene ring and leather washer the hydraulics stopped drifting down. Today I get drifting down. Should I have also replaced the hydraulic cylinder?
 
(quoted from post at 14:23:39 02/10/16) Still struggling with hydraulics and trying to learn. While testing hydraulics today I noticed when the Position(drawbar)control lever is in the horizontal position and I apply pressure or a down force on the lever the back blade will lift all the way up and stay up. Once I release the pressure of pushing down on lever the back blade starts to drop. Also after I replaced the piston with the new setup with neoprene ring and leather washer the hydraulics stopped drifting down. Today I get drifting down. Should I have also replaced the hydraulic cylinder?
Click to expand...

You need to get your head around teh concepts of draft versus position control.
  • [*:5b6afc9ceb] When the lever is in teh vertical position the 3pt is in position control mode. This mode of operation keeps teh implement (mower) at a set height as you mow across uneven terrain. This is accomplished by an internal linakage that senses any change in the lift position and commands the pump to "lift" or "lower" as needed to maintain the set position. [*:5b6afc9ceb]When the lever is in the horizontal position the system is in draft control mode. This mode is principally used for plowing and it allows the operator to set the amount of "draft" or drawbar pull the plow is producing in order to maintain traction and avoid spinning the wheels when the plow encounters hard soil or some sort of obstruction (root, rock, etc). This mode uses an external feedback linkage (through the big spring at at the top of the 3pt) which raises the plow when draft increases and lowers it when draft decreases.[/list:eek::5b6afc9ceb]

    When you put the lever in the horizontal position and push down on it you are confusing the system and it commands the pump to raise the "plow".

    Now is that clear as mud?

    TOH

    PS> If your leak down has returned take the inspection cover off and check for leaks coming from the piston.
 
Thanks TOH for the quick reply. I removed the inspection cover and did not see any leaks. However, I reached in and moved the control arm with my hand and the hydraulics seemed to work perfectly. Any advice?
 
(quoted from post at 17:17:58 02/10/16) Thanks TOH for the quick reply. I removed the inspection cover and did not see any leaks. However, I reached in and moved the control arm with my hand and the hydraulics seemed to work perfectly. Any advice?
Click to expand...

Yes - provide more details in your descriptions and take one problem at a time ;-)

You have a drift down problem - take that first. You need to raise a load with the lift and look for leaks while it is drifting down. Was it leaking down at the time you were looking for leaks? Looking at an unloaded lift that is holding won't tell you much. Put 400# on the lift if you can and check for leaks while the lift is drifting down.

TOH
 
I put about 400lbs load on tractor with carryall. Used touch control lever to raise carryall and only lifts part way. Reached in inspection port on right side and pulled on lift control arm and carryall lifted to top. Turned off tractor and looked for leaks while holding control arm and non were visible. The carryall stayed up until I let the control arm go. I drained the hydraulic oil and adjusted the quadrant according to figure fo136 on page 91 in the IT ford shop manual. Filled with hydraulic oil again and made no difference.
 
(quoted from post at 16:07:18 02/11/16) I put about 400lbs load on tractor with carryall. Used touch control lever to raise carryall and only lifts part way. Reached in inspection port on right side and pulled on lift control arm and carryall lifted to top. Turned off tractor and looked for leaks while holding control arm and non were visible. The carryall stayed up until I let the control arm go. I drained the hydraulic oil and adjusted the quadrant according to figure fo136 on page 91 in the IT ford shop manual. Filled with hydraulic oil again and made no difference.
Click to expand...

[b:7ab4e33e78][u:7ab4e33e78]Assuming you had it in position control mode[/u:7ab4e33e78] [/b:7ab4e33e78]it seems pretty straightforward to me. The lift raises and holds fine when you reach in and operate the valve directly. When you release your hold on the valve it drops to an intermediate position (and holds???). Based on that the control valve linkage needs to be tweaked to get maximum lift and hold at the full up position. It may be the quadrant adjustment is still not right, the friction disk is slipping, and/or it may be an internal linkage problem. All of that is covered at great length in the manual.

TOH
 
Thanks again TOH. I removed the top cover and looked at all the linkage. This time I found that the cam follower pin is badly worn. Any ideas were I may be able to get a replacement and possibly a part number that fits a ford 8n? Looked on yesterdays tractor parts and can not locate. Thanks, Tom
 
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