MF 40 Power Steering

nosteer · Aug 28, 2012

Does anyone have a clue as to why my tractor won't steer" After removal of the pump and replacing the shaft seal, I have topped off the fluid several times and the only way it works is to keep rotating the steering right and left many times then it will catch and work a short while. Then I rev the engine and do the steering wheel rotation and it catches again, but only for a few seconds. I have the Plessey type pump.

mike paulson · Aug 28, 2012

sounds like something came apart in your steering gear/box. when you turn the steering wheel and it freewheels as you described does the steering linkage move?

DavidP, South Wales · Aug 29, 2012

Hello,
As a general answer to your question;
Not sure which type of PAS you would have but its likely to be the hydraulic cylinder acting on a shaft on a pedestal in front of the radiator.
If it is, remove the front grille. Have an assistant work the steering wheel back and forth and check all linkage, ball joints etc from the steering box forward. Look for any wear in the balls or bushes etc. When you get to the cylinder it will have a spool valve mounted on it. This spool valve must move back and forth before you try to move the main steering linkage. This gives you hydraulic activation. If you don't have this spool movement you will be on manual steering. There is an adjustment to control the amount of movement on the spool but there should be no play or wear anywhere else.
DavidP, South Wales

nosteer · Aug 29, 2012

No, It's all hydraulics. The control that is attached to the steering wheel has 4 hyd hoses connected to it. I thought the problem was air in the hyd system but I have refilled it over and over using the instructions in the manual. The steering wheel goes from free movement to rather hard movement. All at once, the system works and will keep working as long as I keep the steering wheel moving R_L or L-R. If I stop, then it quits working again. When It is working, the steering turns relatively easy.The only mechanical linkage is the tie rod. It has a left and right cylinder that is driven by the pump thru the control unit under the steering wheel
Thanks for your input.
Gary

MKinOntario · Aug 29, 2012

It takes a very long time and a lot of fills to get all the air out and the system topped up if it was really empty. Lift the front wheels off the ground while you turn back and forth. It will help. Turn it completely from left to right and back, but don't run up against the stops. If this doesn't do it, there are other problems. Did it work OK before the pump seal replacement? If so, it's likely just low fluid.

nosteer · Aug 30, 2012

Thanks for your info. I will surely try that and yes it worked fine before the repair. I'll get back.
Gary

MF 40 Power Steering

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