3 point drifts down

[jamfu]

Hey fellers. I got a 51 8n. The 3 point has started slowly falling when I am cutting. In your experience is the culprit most likely the ram piston rings, a seal somewhere else inside the pump, or the relief valve ball/spring?

 

[old]

Most of the time it is the cylinder rings that cause that but one never knows for sure unless you pop the inspection plate off the right side and have a look see

 

[notjustair]

Yes.

It could be all kinds of things after this many years. Time to take off the dipstick cover and see what's going on in there while it's drifting down. Mine was cylinder and rings.

 

[ZANE]

TROUBLE SHOOT THE 8N LIFT BY ZANE
BEFORE DOING ANYTHING TO THE LIFT IT SHOULD FIRST BE INSPECTED FOR ANY INTERNAL LEAKAGE. GOOD ADJUSTMENT CAN BE DONE WITH A LEAK IN THE SYSTEM BUT FOR GOOD OPERATION AND IN ORDER TO TAKE FULL ADVANTAGE OF GOING INTO THE LIFT IT SHOULD BE DONE FIRST BEFORE ANYTHING ELSE IS DONE.
BE SURE THAT THE LIFT IS FULL OF OIL AND THAT THE OIL IS CLEAR AND HAS NO WATER IN IT. WATER CAN CAUSE FREEZING AND VALVE SEIZING ETC. NOT GOOD!
BE SURE THAT THE PTO IS ENGAGED UNLESS YOU HAVE ONE OF MY LIVE HYDRAULIC DEVICES WHICH WILL ALLOW YOU TO USE THE THREE POINT HITCH WITHOUT THE PTO IN OPERATION OR THE CLUTCH ENGAGED.
THERE IS ALSO THE REMOTE POSSIBILITY THAT SOMETHING IN THE PUMP DRIVE MECHANISM IS BROKEN SUCH AS THE SCOTCH YOKES THAT THE PISTONS ARE ATTACHED TO.

The pump is a four cylinder piston pump. When the pump jumps on lifting it a sign that one or more of the four pumps is not pumping. Can be a broken valve spring in the side pump chambers or it can be a sign of a broken Scotch yoke that carries the pistons in the pump. Best way to fix it is to drop the pump out the bottom after the oil and PTO shaft has been removed.
TAKE OFF THE RIGHT SIDE INSPECTION PLATE THAT HOLDS THE DIP STICK FOR THE DRIVE TRAIN OIL LEVEL AND START THE TRACTOR WITH AN IMPLEMENT ON AND LOOK FOR A BAD LEAK COMING FROM ABOVE OR THE ABSENCE OF MOVEMENT IN THE CENTER OF THE PUMP AREA. IF NOTHING IS MOVING IN THE CENTER OF THE PUMP AND THE PTO IS TURNING YOU PROBABLY HAVE SOMETHING MAJOR BROKEN ON THE PUMP. YOU CAN LET OUT ENOUGH OIL TO SEE THE MOVING PARTS OF THE PUMP TO BE SURE WHETHER OR NOT IT IS IN FACT WORKING OR NOT. HARD TO TELL WHEN COVERED BY A COUPLE OF INCHES OF OIL.
I think that you are probably having a combination of problems which is common to the 8N lift. One of the worst offenders when it comes to the adjustment is the cam follower pin which is what the position control receives it's input from. If it is badly worn the lift can't possibly work right until it is replaced.
The other thing is to look for a leak in the system @ the ram cylinder rings etc and the pressure relief valve. To check the pressure relief valve find it under the oil and then cut a length of rubber hose that will just slip over the end of the relief valve and have enough length to be raised above the oil level. Start the engine and observe if any oil comes out the end of the hose with a load on the lift arms. To replace the relief valve you should remove the left side inspection plate that also holds the PTO shifter. You will be able to see how to put it back in mesh when you look at the mechanism. Not complicated.

To check the pressure relief valve.
Remove the left side inspection plate off that holds the PTO shifter. The shifter will go back with a little observation on fitting the lever into the slot for it. You can look from the opposite side to make sure it goes back right. Take a piece of rubber fuel line hose that will slip tightly over the end of the relief valve and the while lifting a heavy implement and holding the end of the hose above the oil inside the left side inspection hole see if any oil is escaping the relief valve. If oil comes out the end of the hose the relief valve is leaking and should be replaced. It may take a couple of minutes to fill the hose so don't just do it for a few seconds and think you have done it right.

To remove a faulty relief valve with the oil still in the reservoir. 
Bend an 11/16" boxed end wrench at a 45% angle and reach in and feel for the relief valve under the PTO shaft. Once you have loosened it a bit it should turn out by hand. It is a tapered thread sort of like a pipe thread. There will be a spring and a valve on the inside end of the relief valve that will come out with it. The spring is press fitted to the relief valve and holds the check valve that is designed to hold the oil in the pump when it is not in operation. 

A couple of things you can try to check out is first the pressure tube that is pressed into the housing and goes from the boss just above the pump to the boss just below the lift cover housing. These can rust enough to spring a leak. Sometimes hard to find???? One way you might try to look for a leak in the tube and or a blown gasket at the pumps base is to remove the lift cover. Push the control valve into the pump to the lift position and hold it there or have someone else hold it in. Or wedge something against the rocker to hold it in. Then apply air pressure to the opening on the top end of the pressure tube to see if it bubbles around the tube down under the oil. Either place will bubble if in fact the pump gasket is blown at the tube or the tube has a hole in it. If there are no bubbles there then you might be able to see the bubbles somewhere else to give you a clue as to what to look for. The control valve has to be in the in/up position for this test to work. Otherwise the air will just come out the control valve.
There could be a gasket leaking somewhere such as under the ram cylinder where it mates to the lift cover housing. If this gasket is blown you will see a lot of oil cascading down from above when the lift is applied to an implement while observing through the right side inspection plate. If you decide to take the lift off to work on it be sure not to remove any bolts or nuts except for the ones around the outside perimeter of the cover. If you should remove a bolt that has fine threads it will be from the inside pattern and you should put it back in the same hole it came from. You can remove them after the cover is on the work bench if it becomes necessary to remove the ram cylinder for repair.
When the lift won't come down it is a sure sign that you have dirty oil in the hydraulic reservoir or that the return spring which is under the intake valve is weak and needs to be replaced or stretched out again to increase it's tension.
EXHAUST CONTROL VALVE SPRING DAMAGED OR MISSING
There is a more rare condition that will really put a monkey wrench into the operation of the lift on the 9N/2N AND OR 8N. This is when the retaining spring that is an integral part of the exhaust control valve breaks or becomes too weak to actuate the exhaust valve when it is moved by the control linkage. The spring is located on the exhaust valve itself and has to be intact in order to move the valve when the linkage is moved. It may be necessary to pull the pump in order to inspect and repair the exhaust control valve.
134 oil is great but it can make a small leak worse because of it being a lot less viscose.
You should first take off the right hand inspection plate under the seat on the side of the lift housing. First inspect everything by eye and with a mirror to look at the upper parts for any obviously damaged parts. Move the touch control handle and observe if the control valve is moving in and out of the pump. If the valve is stuck you may be able to get it to working by moving it back and forth with the hand inside the housing till it is loose enough to move with the touch control only. With an implement on the lift start the engine and with the lift in the up position look inside and see if there is oil leaking from the end of the lift ram cylinder. If there is only a slight drip this is normal. If there is a fairly steady stream this may be the trouble. If the oil is coming from somewhere else try to pin point its origin. If you find no appreciable leaks on top in your view then you may have a pressure relief valve leaking. It is located just under the PTO shaft on the vertical back of the pump. Sorta shaped like a spark plug and an 11/16" box end wrench fits it. You can check it for leakage by first finding it with the engine off and then with the pump running and with a load and hot put your finger over the end of the relief valve and if it is leaking enough to be a problem you will be able to feel the oil push your finger off the end of the valve slightly. You can check it by first removing it from the pump then washing it up and soaping it real good with some dishwashing detergent and water and apply air to the end that goes into the pump. If it is leaking you should replace it with a new one. The part # used to be 8N638.
There is always the remote possibility that the pump housing is cracked. This ain't good! To my knowledge a cracked housing is just about done. The cracks usually appear where it is impossible to get to weld and the housing must be replaced. Don's Just 8Ns has them I think or could tell you where to find one if needed. I have a method for testing for a crack. I tapped the outlet pressure hole to accept a 1/4" pipe thread so a grease fitting can be screwed into the outlet hole in the pump flange. Use a grease gun to pressurize the pump with the control valve pushed in to the up position and observe if the grease gun can continue to be operated slowly until the relief valve allows grease to escape out the end of the relief valve. If it can't be pumped up enough for the relief valve to open then look for grease escaping somewhere behind the relief valve and usually under the pressure chamber behind the relief valve. This is a crack if it shows grease escaping anywhere else in the housing and can't be fixed to my knowledge because of the placement of most cracks I have seen in the N pump. The housing must be replaced usually. There could also be a gasket blown out and leaking. If it is in the upper portion of the lift you will be able to see the oil streaming down and this will give you some idea of where it is coming from. Then you can fix it when you get into the cover. Sometimes the pump gasket itself can blow out where the pressure line inters the lift housing on the bottom of the housing. When it blows inside it is just about impossible to determine what the cause is of a very weak lift until the pump is pulled from the tractor. If no other source of a leak can be found it is always possible that the pump gasket has failed internally. The only way to fix it is to remove the pump and clean both the mating surfaces of old gasket material and replace the pump after cleaning with a new gasket and hope for the best.
Hope this will give you some starting places. Zane in Al.
If the lift does not lift to the top of it's travel when the touch control handle is raised all the way up then you have linkage problems. Wear and or abuse can bend and wear parts of the linkage to cause this condition. If the lift needs to be adjusted you will need instructions and a jig to allow you to do the adjustments.
See my web site at http://my.att.net/p/s/community.dll?ep=16&groupid=220626&ck=
ZANES LIFT STUFF

 

[Bruce (VA)]

If the arms drop w/ the tractor off or the clutch depressed, chances are you have a worn lift cylinder or piston (or both), a blown top cover gasket or a leaky pressure relief valve. Take the inspection plate w/ the dipstick off. Lift a heavy implement & look inside w/ the tractor running & the PTO engaged to see if you notice oil running from the top cover. If oil is running steadily from the top cover the chances are the lift cylinder needs to be rebuilt. It’s less likely, but a possibility, that the top cover gasket is bad. (It’s very difficult to detect the exact source of the oil leaking inside of the top cover while looking through the inspection port). If no oil is running down from the top cover, look at the rear of the pump in the oil with the load still on it and see if you notice turbulence in the bottom. (Some movement of oil will be normal with the PTO shaft turning). You could have a weak pressure relief valve which will be detected by turbulence in the oil. To check for a slow leak, lift a heavy implement, turn the tractor off & put a ½ inch clear plastic hose on the end of the valve & stick the other end of the hose through the inspection port. With pressure in the pump, a bad valve will likely show some fluid in the hose.
75 Tips

 

[Dan-in-MO]

Another possibility....contaminated hydraulic fluid might be foaming allowing air into the system.

 

[Bob Huntress]

I have to ask if you can see any hydraulic fluid leaking from the tractor? Most likely you either have a leak external, such as cylinder seal, or an internal leak, like your control valve. When you place the lift into position and the valve and cylinder are properly operating the fluid pressure holds that position. In order for the weight of the 3 point hitch to drive the unit downward fluid would need to leave the space between the control valve and the cylinder. Air can cause a slight drop, but if the system has integrity the drop will reduce as the air compresses. The question is where is the system pressure leaking?

Note 1- When lifting with the hitch, you should be able to view the reverse of the air effecting operations.

Note 2- If your leak is external, expect air to be entering the system when the pressure is reversed in operation.

 

[souNdguy]

if it's dropping WITH the pto engaged.. i'd check to see if the 3pt controll is loose and dropping in the quadrant. if it is.. the lift will drop too

your messages seems to indicate it is dropping while cutting.. thus pto running..

post back

 

[jamfu]

Ok thanks guys. next time im out at the farm I will check the ID 10 T codes first. I suspect it is prolly the cylinder rings. But thanks for all the input. I 'll keep ya'll posted.
Jim

 

[souNdguy]

post back and let us know.

leaking down when pto IS turning is a whole different ballgame than leaking down when pto not turning.

 

[TheOldHokie]

(quoted from post at 10:27:38 12/12/12) post back and let us know.

leaking down when pto IS turning is a whole different ballgame than leaking down when pto not turning.

The only difference I see is the leak is faster????

TOH

 

[souNdguy]

think about it ....

if it drops down when the pto is not turning, it can be leaks in lots of places. cyl, relief, gasket, stand pipe.. etc. something, somewhere is leaking.


now.. if it drops when the pto is running.. that means 2 things.

1, it went up in the first place, thus.. the pump flow is greater than the leak and 2, something changes so that the pump flow is less than the leak.. If mowing, as the op said.. that means he's near rated speed, and thus pump is turning out near max of 2.8gpm.. that means.. theyt the 'leak' is now exceeding that.. but.. wasn't before. could be a hold / cold oil issue..

could be a bunch of leaks working together.. like a dirty sump that is sticking a relief and whatnot.

could be his tension washer is worn, and letting the 3pt control handle slip down, and thus drop the lift normally.


that's whay I asked him to post back some more details.

 

[TheOldHokie]

(quoted from post at 11:03:47 12/12/12) think about it ....

if it drops down when the pto is not turning, it can be leaks in lots of places. cyl, relief, gasket, stand pipe.. etc. something, somewhere is leaking.


now.. if it drops when the pto is running.. that means 2 things.

1, it went up in the first place, thus.. the pump flow is greater than the leak and 2, something changes so that the pump flow is less than the leak.. If mowing, as the op said.. that means he's near rated speed, and thus pump is turning out near max of 2.8gpm.. that means.. theyt the 'leak' is now exceeding that.. but.. wasn't before. could be a hold / cold oil issue..

could be a bunch of leaks working together.. like a dirty sump that is sticking a relief and whatnot.

could be his tension washer is worn, and letting the 3pt control handle slip down, and thus drop the lift normally.


that's whay I asked him to post back some more details.

Still don't follow your logic. We are talking about finding the source of a leak down. It went up because the pump was pumping faster than the leak down as opposed to it went up even though the pump was pumping slower than the leak down?? I don't think so.

So in [u:9069ece862]all[/u:9069ece862] cases the leakage is less than pump output. If it only leaks down with the pump off it's just a small leak. If it leaks down with the pump running at half RPM but holds at full RPM it's just a little larger leak. If it will lift with cold oil but won't hold even with the pump running full RPM once the oil warms up it's just a large leak that got a little faster with warmer oil. In none of these cases are we going to look anywhere different for the leak.

TOH

 

[souNdguy]

your first paragraph shows that you din't parse what I typed. you said something I didn't say.. there was a conclusion drawn i expressly did not make..

he also said mowing. we are not talking about half rpm.

he has some issue that lets him lift the mower and mow, and then, he's no longer able to keep it lifted.

it's either a leak that gets worse with temperature ( oil?) or the lift is simply dropping because it's been told to.. like the 3pt lever dropping.

I have personally answered about 15 posts on the subject here, and other forums, trying to help someone determine why their lift won't hold, yada, yada only to later find they omitted mentioning that their 3pt handle was sloppy and vibrated down many times. they saw no corelation to the handle going down and the lift going down.. they were simply told if the lift went down it was a leak.. so thay approached it from that aspect.

that's why i asked the guy if the handle is dropping.
he hasn't answered.

without that bit of data.. we cannot make a 100% correct statement that his problem is a leak.

that's my entire point. .. and why I asked some specific questions.

 

[TheOldHokie]

(quoted from post at 13:23:13 12/12/12) your first paragraph shows that you din't parse what I typed. you said something I didn't say.. there was a conclusion drawn i expressly did not make..

Fine. I miss-interpreted what you wrote.

TOH

 

[souNdguy]

besides.. i think we are all getting ahead of ourselves untill the user posts back. right now it could be anything from a 2$ fix and up... once he posts back.. who knows...

does make you wonder what oil he is using... and if it has water in it or not...