MF 251 XE Hydraulics Issue

D

Dave E

New member
Hello all. Bear with me this will take a minit.
I have a 2000 model 251XE I have owned since it was 2 years old with a Bushog loader on it I installed years ago. Past few years intermittently lift arms would fail to rise or would drop. Would only raise at idle. When reved up they would fall. Eventually split tractor and went through pump out of desperation and found no fault, reassembled and had same issue. Now the loader sounds and acts like it has air in system, growls and is jerky, it has an auxiliary pump inside.

What we have determined, by running the tractor with the lift arms and top removed, for some reason the main pump is aerating the fluid, and the aux pump suction is picking it up causing the aeration issue.
This tractor has a small tube that runs from the tri angular cast cover underneath which secures the strainer, to a pressure/vacuum switch under the seat with a wire connected to it that is supposed, somehow to turn on a light on the dash if the strainer starts to plug up.

Now the interesting part. When the switch is removed from the small tube and allowed to be open, it pulls a vacuum on it, and this is causing the fluid to aerate and the loader growls, BUT, with it open, the rear lift arms operate as they should. If you plug the line off so no vacuum flows, aeration does not occur, the loader operates as normal, no growling or jerking, but the lift arms will not raise, only at idle with they attempt to rise.
I can find no one that can tell me how this little tube/switch outfit is supposed to work, or be affecting this system, or how to fix this thing. It has in its previous years I have owned it worked perfectly fine and no one has done any hokey foolin with it.

Sorry for long post and thanks for reading and any help or insight anyone may have or who might know. Thanks Dave.
 
As I see it, the "light" involved is a waste of time. If the system works with the tube plugged off, then plug it permanently and get back to work. Massey has been building those tractors for over seventy years using the same lift system without any "idiot" lights and gotten by just fine. When the screen gets plugged the hydraulics will tell you without any lights.
 
I get it. I agree. But it doesn’t work properly with it plugged off or open. As I stated, when it’s plugged the auxiliary system works perfectly, and the 3 point doesn’t. When it’s unplugged, the 3 point works right but the auxiliary system is aerated causing it to growl and be jerky.

Can find no diagram of this system. My manual doesn’t even show an illustration with it being there. Thank you for your response!
 
I'm not sure what "diagram" you're hoping to find. As I see it, that model was made in Brazil. Some tractors built down there are mostly similar to UK built units, but not entirely. The parts book shows two lift pumps. One made in UK and the other ??? Could be made locally.

That said, I ran into something similar a couple of years back on a 270. (that too, is a bit of an Bastard child compared to other models) I couldn't get the lift to work. Spent days working on it, rebuilding the pump (twice) had it apart numerous times. It has a very similar lift pump suction manifold to what the book shows for the 251xe, in that there is a valve of some sort in there that I could never find or figure out the purpose of/for. I tried it with the valve tied open, tied closed, out entirely, and couldn't make the pump work. For some reason the pump wouldn't pull oil through the suction screen without the vacuum created moving the control valve spool to the lower position. As such, the lift would start to work if I cranked the engine with the starter, but as soon as the engine started the lift would drop again and never come back up. I finally determined this was happening and tried it without the screen. It worked fine like that. Whether the valve I mentioned had anything at all to do with the problem, I never figured out. What I ended up doing was modifying the screen so it could draw fluid into the pump with less restriction (and yes, slightly less filtration) and it has been working ever since. I would suggest you try that. Just drain the oil, remove the screen entirely, put the oil back in and try it. It may be no help at all, but you won't know unless you try it.
 
Update on hydraulic issue. Drained system oil down again to removed side plate and ran tractor to acertain that the pumps, valve and levers were operating as designed. Found no fault there so took your advise and removed the strainer all together, refilled with oil. Started up and everything worked normally. Don’t know what the deal is with the strainer, as it doesn’t look dirty but something doesn’t look right about it even after washing in parts washer. Can barely see light through it. Looks as though it has been subjected to some serious suction which it probably has. Am to pick up new strainer at dealer tomorrow and will update after installation.

Another thing that has happened unrelated, is I refilled with Traveler brand Universal Tractor fluid back in early December. The tractor has been used once and now the seals in the power steering cylinder have started pouring oil, just sitting there. (Added a tad over a pint to the reservoir), at the time to top off. Seals in the rear SCV connections have swollen up and popped out. Has not affected Bush Hog loader or two other cylinders I installed for top and side link. Yet! Even though it says MF approved on the pail this Brazilian made unit don’t like it! I imagine when I replace the seals they will be compatible, though I will be using oil from my dealer.
 
Interesting developments on both counts. I've put many gallons of Traveler UTF in a great many tractors and have never had that result. I'm curious about how the new screen thing works out. If the new one looks like this one, I would be tempted to return it. Order one with a different part number, one from another 200 series tractor made elsewhere.
 
Dave E said:
Update on hydraulic issue. Drained system oil down again to removed side plate and ran tractor to acertain that the pumps, valve and levers were operating as designed. Found no fault there so took your advise and removed the strainer all together, refilled with oil. Started up and everything worked normally. Don’t know what the deal is with the strainer, as it doesn’t look dirty but something doesn’t look right about it even after washing in parts washer. Can barely see light through it. Looks as though it has been subjected to some serious suction which it probably has. Am to pick up new strainer at dealer tomorrow and will update after installation.

Another thing that has happened unrelated, is I refilled with Traveler brand Universal Tractor fluid back in early December. The tractor has been used once and now the seals in the power steering cylinder have started pouring oil, just sitting there. (Added a tad over a pint to the reservoir), at the time to top off. Seals in the rear SCV connections have swollen up and popped out. Has not affected Bush Hog loader or two other cylinders I installed for top and side link. Yet! Even though it says MF approved on the pail this Brazilian made unit don’t like it! I imagine when I replace the seals they will be compatible, though I will be using oil from my dealer.
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Fedup said:
Interesting developments on both counts. I've put many gallons of Traveler UTF in a great many tractors and have never had that result. I'm curious about how the new screen thing works out. If the new one looks like this one, I would be tempted to return it. Order one with a different part number, one from another 200 series tractor made elsewhere.
Click to expand...
It is definitely a suction issue, as that is the cause of the lift arms raising very slowly at idle yet soon as you gas up on it they fall. What is happening is there is a check valve on the suction manifold for the pumps, that the strainer is affixed to. When it is at idle, pump is able to get enough fluid to work, somewhat. When it comes off idle, the aux pump shocks the check valve, it pops open dumping the fluid from the spool valve, causing the arms to drop. Check will not shut again until rpm’s are reduced.
The little tube that operates the pressure switch for the light, runs through the triangular cap underneath, leads directly to the center of the strainer. That’s why it pulling a vacume on the tube because something is wonky, that I can’t see, with the strainer. With the strainer out no vacume is pulled on the tube, thus no air introduced into system to be picked up by aux pump.
We shall see.
 
I won't argue your theory in this case, as I have never seen the pump in this model. However, my experience with this problem was on a 270, which as I recall had no such circuitry and no light. The pump strainer on this model is like nothing I've ever seen on any other Massey model, based on what I see in parts breakdowns.
 
Fedup said:
I won't argue your theory in this case, as I have never seen the pump in this model. However, my experience with this problem was on a 270, which as I recall had no such circuitry and no light. The pump strainer on this model is like nothing I've ever seen on any other Massey model, based on what I see in parts breakdowns.
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Man I really don’t know myself. I have owned and worked on numerous smaller MF tractors and haven’t seen a couple of things that this one has. Neither has my dealer, and they have been a family owned and operated dealer and shop for over 75 years.
 
When I came across this problem a couple years back it was my first time with this particular issue. Seemed simple enough. Pump's not working. Remove it, overhaul it and be done with it. I split that tractor at least three times, had the pump apart two or three times and couldn't make any sense of it. After I figured out the screen was involved, modified that and got it working again, I went looking for answers. I concluded the pump suction was actually sucking the control valve spool into the "lower" position against spring tension, but I didn't understand why. And why it worked for thirty years without a problem then changed. I went one on one with a few knowledgeable Massey guys on various forums, and not one could explain it, or had ever seen it.
 
That is crazy for something to work for years as these things do, and then suddenly give problems that quite a few people have seen, but few can truly figure out. Especially being that comparatively, the system is really quite simple with few parts with all mechanical controls. Thank you for your informed responses and I will provide updates.
 
Latest and final update. Installed new strainer purchased from our local MF dealer and tractor operates as it was designed. I am going to explain how the strainer causes the lift arm raising issues. Hold on it will take a few minits.
When the tractor is sitting not running with everything static, and the quadrant levers in the down position, the spool valve is pushed into the "arms lifting position" by the oscillator and drawback spring, since there is no pressure being made. When the engine starts, the pump pulls a suction on the spool valve overcoming the tension of the spring until the spool valve is pulled to the neutral position, ( This is why when you first start your tractor the lift arms will "jitter" upward for a scound or so until a balance is obtained between the spring and the suction of the pump). pulling a suction on the manifold, opening the check valve and pulling fluid through the strainer. When the balance is obtained the spool is in the neutral position, the check valve closes and the fluid from the pump is dumped through the pump response control unit back into the tractor. Now we are geting to why the arms drop when the tractor comes off idle.

The auxilary pump draws oil from the same manifold as the main pump. Remember the check valve in the manifold. When the engine comes off idle, the auxilary pump pulls a suction on the manifold, and over powers the spring in the check valve because the strainer is resticted. When this happens, the check valve becomes unseated and pulls a suction on the spool valve, overcoming the oscillator and drawback spring, causing the spool to be pulled into the lowering position and the arms fall. And it all stays this way because the auxilary pump is making the oil take the path of least resistance until you stop the engine and the check and oscillator spings "reset".

Thats why the lift arms on the 270 would raise when the starter was engaged. Then fall when engine kicked off and aux pump pulled a strong enough suction to over come the springs in the control valve and check valve. Also why arms will sometimes raise slowly at idle because it can get enough fluid to operate somewhat albeit slowly. Then soon as its gassed up, auxilary pump starts pulling hard and overcomes springs because of restricted strainer. If you look at the hydraulic flow diagram for this tractor it all makes perfect sense after some study.

My strainer looked good, until I placed a new one beside it. You could also cover one end of the old strainer and hardly be able to blow through it by mouth. New one was like blowing through a barn door.

I thank you very much for your informed and very knowledgable responses. It would have taken me a long time to think in a different way had you not shared your ideas and thoughts. Good Man!! Thanks!
 
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