MASSEY FERGUSON MF 260, Care Instructions, Page: 39 / 48

7
Chapter 19
Hydrostatic Power Steering System
39
B. Turning of the Steering when the Engine is Running :
On first movement of the steering wheel the right and left turning holes become straight
with each other, so that oil can be supplied to the oil hand pump. Subsequently, the
second movement turns the steering and the hand pump. Simultaneously, the hand pump
measures the quantity of oil and pushes it back towards the spool and sleeve. The oil
coming back enters the spool valve through the grooves, which connect the holes together
straightly so that the oil could go to the direction in which the steering wheel was turned.
With the spool valve and sleeve holes being face to face with each other, the oil coming
back from the steering cylinder returns to the circuit. The relief valve between the inlet and
the spool inside the steering unit, which protects against the high-pressure created inside
the pump, for example, due to an obstruction while the front wheels are turning. From the
steering pump to the steering unit, there is a check valve installed on the way. This is a
one-way valve that prevents high-pressure while the steering is being turned.
C. Turning the Steering when the Engine is OFF :
The pump stops working when the engine is turned off, due to which the oil starts to pass
through a bypass valve installed inside the steering unit between the supply and return
holes. As the pump starts to function, the oil pressure shuts off the valve by pushing it onto
its seat.
When the pump cylinder is low, the oil returning from the steering cylinder towards the
valve inlet side is bypassed. With the help of this function, the oil can move from one side
to the other inside the steering cylinder to maintain uninterrupted steering control.