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Massey Ferguson 6614, 6616 hydraulic system - Lift control spool valve
The BOSCH ELC (EHR5) lift control spool valve is installed to Massey Ferguson 6614, 6616 tractors equipped with an open centre hydraulic system. It is fitted to the left-hand hydraulic cover of the centre housing.
It regulates the flow rate of oil to and from the lift rams, according
to the signals that it receives from the electronic linkage calculator
(ELC). It comprises a series of spools and valves, most of which cannot
be repaired as separate parts.
Layout of components and identification of
ports
The BOSCH ELC (EHR5) hydraulic spool valve comprises two parts:
Hydraulic part and Electrical part.
Hydraulic part - (1) Non-return valve (2) Lifting spool valve (3)
Lowering spool valve (4) Flow rate control spool (5) Shock valve (200 to
210 bar) (6) Flow control spool spring (9) Lifting spool spring (10)
Lowering spool spring (11) Restrictor (12). Lift control spool valve
Identification of ports: N - Continuity channel, P - Pressure, R, R1 -
Return to housing, V - Port to lift rams. Electrical part - E(7)
Lowering solenoid valve (8) Lifting solenoid valve
To tell a MF 6614, 6616 hydraulic problem apart from an electrical
problem, operate the push-buttons at the end of the solenoid valves.
This allows to manually
control solenoid valve movement.
Neutral position
When the engine is stopped:
- the lift control spool valve (12) is in neutral position;
- the lifting and lowering solenoid valve spools (2) and (3) are held in
position by their respective springs;
- the flow rate control spool (4) is held down by its own spring
When the engine is running:
The hydraulic pump supplies the lift control spool valve (12) via the
trailer braking spool valve (13) (if fitted) and the auxiliary spool
valves.
The pressure arriving
from the port (P) moves the flow rate control spool (4) upwards, thus
allowing the oil to flow into the continuity channel (N) and the
hydraulic pump via the transfer
pipe.
The continuity channel (N) connects the oil flowing in the MF 6616, 6614
Open Centre system and also controls the hydraulic flow of brake
lubricant via a restrictor
and a valve.
Lifting position
The solenoid valve (8) is activated to lift the drawbars. The lifting
spool (2) is moved downwards, thus directing the main flow to the
non-return valve (1).
As soon as
the pressure acting on the valve exceeds the pressure in the rams, the
valve opens and the flow enters the port (V) to raise the hitch.
When the hitch is in the required position, the Massey Ferguson 6616,
6614 tractor electronic system stops the supply to the solenoid valve
(8).
As a result:
- the non-return valve closes;
- the lifting spool valve is positioned on the return channel R1;
- the flow rate control spool (4) is fixed in raised position, allowing
the oil to flow again in the continuity channel N.
Lowering position
The solenoid valve (7) is activated to lower the drawbars. The lowering
spool (3) is moved downwards. Its position allows oil to return from the
rams via the port (V)
to the return R1.
The lowering phase has no effect on the flow rate
control spool (4). The continuity flow rate N is thus directed to the
pump via the transfer pipe.
Shock valve
Location
The shock valve is housed at the front bottom of the left-hand hydraulic
cover.
Function
It directs oil from the rams to the return in case of overpressure in
the circuit. Hitch bounces when transporting an implement.
Characteristics
The shock valve is calibrated at 200 to 210 bar.
Removing and install the spool valve
Immobilise the MF 6614, 6616 tractor. Chock the front wheels. Take off
the rear wheel concerned. Position a safety stand. Detach the fuel tank
from the gearbox or,
if necessary, remove it after draining.
Removal
Identify then disconnect the wiring harnesses from the lifting and
lowering solenoid valves. The lowering solenoid valve is turned towards
the front of the Massey
Ferguson 6614, 6616 tractor.
Mark, disconnect and block:
- the hose from the auxiliary spool valves;
- the supply or return pipe from the lift rams.
Extract the screws and remove the lift control spool valve without
losing the O’rings.
Install
Clean the mating faces of the cover and lift control spool valve.
Replace the O’rings (if necessary).
Reinstall the spool valve.
Install and tighten the screws to a torque of 36 - 46 Nm.
Reconnect: the pipes and hoses, the solenoid valve harnesses.
Attach the harnesses using one or more clip retainers, if necessary.
Attach or reinstall the fuel tank.
Install the wheel. Remove the safety stand and trolley jack.
Start the engine. Check the operation of the lift control system and the
oil tightness of the seals and unions.
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