John Deer 1140 lift arm problem

shaughnessy · Aug 19, 2012

I have a Mannheim JD 1140 that is about 30 years old. Today I hitched up my drum mower to make hay and the lift arms won't lift it off the ground. I've been using the mower for the last few years, and the tractor has never struggled to lift it before. The tractor is very rarely used. I only use the lift arms during two periods each year- in the summer when I make a small amount of hay (c 300 conventional small bales), and in the spring when I use the pick-up hitch with a trailer to muck-out my sheep shed. The lift arms will go up and down if I disconnect the mower. The tractor has a loader, which is working normally. The power steering is also working ok. There is plenty of hydraulic fluid, and the filters where changed last year. From the behaviour of the loader and the power steering I conclude that the hydraulic pumps are OK. Given that the lift arms operate unloaded, but not under the load of the mower, I'm assuming that either a seal is failing under pressure, or that there might be some sort of relief valve that is operating when it shouldn't. I will get the service guys out tomorrow (Monday), but will lose a day's good weather, so if any of you have any suggestions in the meantime about what I might investigate then I'd be very grateful. I don't have any pressure guages, so I can't perform any tests that require them.

Kind regards

J_J · Aug 20, 2012

Every tractor owner should have a hyd pressure gage and know how to interpret the pressure displayed.

Take a reading at the FEL valve and note the relief pressure.

Connect the gage to the input to the 3pt and take some readings.

You could have bad seals in the 3pt piston, the 3pt valve spool could be worn. the relief valve might be bad.

The fluid is apparently going back to tank.

Is your system open center or closed center.

shaughnessy · Aug 21, 2012

Hi JJ,

Thanks for that. I think your advice about pressure gauges is very sensible. the 1140 has a closed centre system. One complication in my case is that the tractor has a Sekura cab, so getting access to the hydraulics is difficult without removing the cab, which is a major job in itself. I've got a friend arriving today with gauges so we'll try to do some tests. I'll let you know what happens.

Denis

shaughnessy · Aug 21, 2012

The symptoms of the problem have suddenly gone away. I tried using the lift arms at different times over two days, and on two separate pieces of equipment, one being a drum mower and the other a hay rake, the latter being much lighter than the former; in all cases the arms failed to lift the equipment. This morning I tried again with no load attached; the arms did rise but only after the control lever was moved almost all the way back. From outside the cab I moved the lever forward about half way and watched as the arms dropped slowly. I don't know why I did, but as the arms were dropping I stood on one of them and put all my weight on it, and suddenly the arms rose right to the top of their travel with me standing on them, even though I was outside of the cab and not touching the lever. From that point on the link arms have worked perfectly. I hitched up my heavy mower and the tractor will raise and lower it perfectly, with no hesitation or tremor. Apart from being relieved that the problem has gone away, I am intellectually curious about what has caused it. I think we can rule out problems with the seals and the pumps. I think I'm left with the following possibilities: 1) a relieve valve being stuck open; 2) some play in the conrols that actuate the lift arm, which has somehow corrected itself; or 3) some interference from the faulty operation of some other feedback mechanism like the load sensing control. I'd appreciate any insights you wiser people might have.

J_J · Aug 21, 2012

Your closed center hyd system will have one of the below setups.

Constant pressure systems, Load-sensing systems.

Constant pressure systems (CP-system), standard. Pump pressure always equals the pressure setting for the pump regulator. This setting must cover the maximum required load pressure. Pump delivers flow according to required sum of flow to the consumers. The CP-system generates large power losses if the machine works with large variations in load pressure and the average system pressure is much lower than the pressure setting for the pump regulator. CP is simple in design. Works like a pneumatic system. New hydraulic functions can easily be added and the system is quick in response.

Constant pressure systems (CP-system), unloaded. Same basic configuration as 'standard' CP-system but the pump is unloaded to a low stand-by pressure when all valves are in neutral position. Not so fast response as standard CP but pump lifetime is prolonged.

Load-sensing systems (LS-system) generates less power losses as the pump can reduce both flow and pressure to match the load requirements, but requires more tuning than the CP-system with respect to system stability. The LS-system also requires additional logical valves and compensator valves in the directional valves, thus it is technically more complex and more expensive than the CP-system. The LS-system system generates a constant power loss related to the regulating pressure drop for the pump regulator:

The system could have fixed itself just by using all the functions. You might try just activating all valves several times a year to keep valves and components from sticking.

shaughnessy · Aug 21, 2012

Many thanks JJ. I suspect the problem is caused by the fact that the tractor sits idle for many wekks at a strech. I've only a few acres of land and about 50 sheep, so I've little use for the JD. For smaller jobs I've a little Kubota, and for even smaller one, such as towing light materials around, I've a JD petrol ride-on mower. Perhaps I should trade them all in for a mid-sized machine that I could use for all the jobs!