Tractor hydraulic system - Right-hand cover plate (57 l/min)


The right-hand cover plate is fitted to the rear axle housing and has two main functions:
- it supports numerous hydraulic system components
- it incorporates various suction and cooling channels of the high and low flow rate systems (high and low pressure).

On its internal face, the cover plate is connected to the:
- two-stage hydraulic pump and its drive gear
- suction pipe
- inlet manifold
- the left-hand cover plate transfer pipe.


On its external faces, it is connected to the:
- four control solenoid valves of the low pressure functions (depending on option). There is a diode in the solenoid of the PTO brake solenoid valve. The PTO clutch is controlled by an on/off solenoid valve.
- safety valve in the high pressure system
- valve for the suspended front axle (if fitted).
- trailer brake valve (if fitted) or a cover plate (depending on option)
- three "diagnostics" connectors
- strainer
- support and main 15 micron filter(s).
- filter switch
- engine speed sensor.

Parts list
(1) Cover plate (2) Screw (3) High pressure (high flow rate) valve (4) Screw
(5) Low pressure 20 bar diagnostics connector (7) On/off solenoid valve (PTO clutch) (8) to (10) Solenoid valves: PTO brake, front and rear differential lock, 4WD (12) Blockage indicator
(13) Support (14) Filters (15) 15 micron filter cartridges (16) Engine speed sensor (17) Low flow rate diagnostics connector (18) Strainer (19) Filter switch
(20) High pressure, high flow rate diagnostics connector (21) Centring pins (22) "O" ring (23) "O" ring (24) Seal (25) Transfer pipe (26) "O" rings (27) Nut (28) Washer (29) Gear (30) Key (31) Screw
(32) Hydraulic pump (33) Pin (37) Deflector (38) Suction pipe (39) Seal (40) Inlet manifold (41) "O" rings (42) Pipe (43) Threaded end fitting (44) Seal



Identification of channels and ports

On the cover plate (1) 

A Channel to auxiliary spool valves
B Port to front and rear differential locks (if fitted)
C 20 bar pressure inlet from left-hand hydraulic cover plate
D Low flow rate channel to main filters (15 microns) and Orbitrol spool valve
E Port to 4WD clutch (if fitted)
F Suction
G Oil outlet to pump via strainer
H Port for filter switch
I Continuity port to auxiliary spool valves
J High pressure port, pump outlet
K Port to PTO brake
L Port to PTO clutch

On the solenoid valves
ON - OFF solenoid valves (8 to 10). Only the solenoid valve (8) (PTO brake) has a diode (+/-).

A Supply ports to pressurised components
P 20 bar low pressure inlet
R Port to the return

On the high pressure, high flow rate valve (3) 

P 200 bar high pressure inlet
R Port to the return

Removing and install the cover plate

Preliminary steps
Immobilise the tractor. Chock the left rear wheel.
Apply the hand brake. Chock between the frame and the front axle (optional).
Partially drain the rear axle housing. Take off the wheel concerned. Place an axle stand in position.

Removal 
Disconnect the blockage indicator harness (12).
Remove the 15 micron filter(s) (14) and the support (depending on option).
Remove the strainer (18) to access the partially hidden screw (4).
If the tractor is fitted with a trailer brake mechanism: Remove the spool valve.


Disconnect and block:
- the hose (1) to the auxiliary system
- the rear differential lock pipe (2) and the hose (8) from the front differential lock control (if fitted)
- the 4WD clutch supply pipe (10) for tractors fitted with this option
- the PTO brake supply pipe (3).
- the steering spool valve supply pipe (9) via the 15 micron filter(s) (14)
- the 20 bar hydraulic cover plate supply pipe.
Disconnect the harness of the engine speed sensor (16) and filter switch (19) 
Disconnect the solenoid valves, marking their connections. The function of each solenoid valve is indicated on the external face of the hydraulic cover plate casing. The cover plate is fitted with two different types of solenoid valves. The solenoid valve (8) of the PTO brake has a solenoid with a diode and is represented by the following symbol (+/-).
Remove the screws (4) and the cover plate.
After removing the cover plate, if necessary, remove the transfer pipe (25) from the housing, ensuring hydraulic continuity to the pump manifold.


 Installing
Clean the mating faces of the housing and cover plate.
Check for the presence of the two centring pins (1) and rivets at the ends of the channels on the cover plate.
Install new seals:
- on the Hare / Tortoise channels (2) 
- on the power take-off clutch channel (3).


Install and position the suction pipe (38), with its notch along the axis of the pin. Install the seal (39).
Screw two makeshift guide studs into opposing holes on the housing.
Install the transfer pipe (if removed), first checking the seals are in a good condition.


Smear the mating faces of the cover plate with a sealing product (Loctite 510 or equivalent) taking care not to block the hydraulic ports of the Hare / Tortoise mechanism. Reinstall the cover plate. Take out the guide studs. Install and tighten the screws (4) to 72-96 Nm.
Reconnect (in accordance with the markings made):
- solenoid valves
- filter switch
- engine speed sensor.
Attach the electrical harnesses with a retainer.
Reconnect the pipes and hose. Reinstall the trailer brake spool valve.
Check the condition of the seal of the strainer (18) and lubricate it. Reinstall the strainer and tighten it an additional quarter turn after it contacts with the seal. Reinstall the 15 micron filter(s) and the support. Reconnect the blockage indicator.

Lift the tractor. Install the wheel. Remove the axle stand and tighten the nuts. Remove the chocks.
Top up the tractor transmission oil level of the rear axle and check it using the gauge located to the rear of the centre housing.
Check the operation of the electrical circuits, the low pressure switch, the solenoid valves, the filter switch and the blockage indicator.
If the pump has been replaced, or if the disassembly of one or several hydraulic component(s) was necessary, check the hydraulic system by carrying out the relevant tests. Check the tightness of the cover plate mating face, the strainer and the hydraulic unions.