Tractor hydraulic system - Left-hand cover plate (100 l/min)



The left-hand cover plate fitted to the centre housing serves as a support for the linkage spool valve. It also supports the pump used for steering and the 17 bar system on its internal face. 

On its external face, it has various channels:
- low pressure to the right-hand cover plate
- cooling and lubrication, to the gearbox
- steering system
- high pressure to the linkage
- return from spool valves and linkage.

On its internal face, a restrictor (1) maintains a pressure of approximately 5 bar to lubricate the braking mechanism in the trumpet housings

A version without hydraulic linkage is available. 

In this case, a plate replaces the linkage spool valve.

Identification of ports 
(A) Orbitrol steering unit supply (pump outlet to 15 micron filter)
(B) Return from Orbitrol steering unit
(C) 17 bar supply (to right-hand cover plate)
(D) Auxiliary spool valve return
(E) Brake lubrication
(F) Cooler supply
(G) Gearbox lubrication
(H) Linkage valve supply
(I) Lift ram supply

Parts list 
(1) Lifting solenoid valve (2) Lowering solenoid valve (3) Linkage valve supply pipe (4) Lift ram supply pipes (5) Cover plate screw (6) Support (7) Temperature switch (8) Screw (9) Support (10) 17 bar connecting pipe (11) Trumpet housing lubrication pipe (12) Low pressure switch (17 bar)
(13) Gearbox lubrication pipe (14) Hose (cooling) (15) Hose (Orbitrol) (16) 17 bar valve (17) Linkage spool valve block (18) Union (to 15 micron filter) (19) Linkage security valve (20) Plug (21) Linkage spool valve screw (22) Pump (23) Seal (24) Manifold (25) "O" ring (26) Screw (27) Gear
(28) Pipe (29) "O" ring (30) "O" ring (31) Circlip (32) Union (33) "O" ring (34) Centring pin (35) Restrictor

Removing and install the cover plate

Immobilise the tractor. Chock the front wheels. Take off the rear wheel concerned. Position a safety stand. Partially drain the rear axle housing.
Detach the fuel tank from the gearbox or, if necessary, remove it after draining.

Removal 
Mark and disconnect the harnesses:
- of the lifting (1) and lowering (2) solenoid valves,
- of the low pressure switch (17 bar) (12),
- of the temperature switch (7).


Mark, disconnect and block:
- the hose (15) from the steering spool valve (Orbitrol),
- the lubrication hose (14) to the cooler (hot oil),
- the linkage valve supply hose (3),
- the lift ram supply pipes (4),
- the hydraulic spool valve (32) and brake lubrication (11) return union,
- the pipe (18) supplying the 15 micron filter,
- the lubrication pipe (13) to the gearbox (cold oil),
- the pipe (17 bar) (10) to the right-hand cover plate.


Disconnect the following controls:
- hand brake,
- GSPTO (if fitted).
Disconnect the pipe (11) to the trumpet housing lubrication (all types). 


Remove the screws (5). Remove the support (6), the support (9) (if fitted) and the cover plate. If necessary, remove the transfer pipe (28).

Preparing for refitting
Clean the mating faces of the housing and the cover plate.
Check that the "O" rings (29) (30) of the transfer pipe (28) are not damaged and refit it on the right-hand cover plate.
Lightly smear the mating face of the housing with a sealing product (Loctite 510 or equivalent). Screw two guide studs "G" into opposing holes on the housing.

Refitting
Refit the cover plate. Fit the hand brake control support (6) and the proportional PTO support (9) (if fitted). Take out the guide studs. Fit and tighten the screws (5) to a torque of 72 - 96 Nm.


Reconnect the pipes, hoses and harnesses removed previously, according to their marks.
Attach the harnesses using one or more retainers. Check that they can move freely and easily. Use cables to connect the controls.
Check the control setting for:
- the hand brake,
- GSPTO (if fitted).

Reattach or refit the fuel tank. Refit the wheel. Remove the axle stand and the trolley jack. Tighten nuts. Top up the oil level in the rear axle and check it on the gauge located at the rear of the centre housing. Start the engine.
Check the operation of the linkage system, the auxiliary hydraulics and the tightness of the mating face, cover plate and hydraulic unions.

Disassembling and reassembling the cover plate

Disassembly
Take off the cover plate.
Place the cover plate in a vice fitted with plastic jaws.

On the external face
Remove: 
- the screws (21) and the linkage spool valve (17).
Mark and remove the unions and plugs remaining on the cover plate.
- the linkage security valve (19).
- the low pressure switch (12).
- the temperature switch (7).
- the 17 bar valve (16). Mark the position of the different seals and washers.

On the internal face
Remove the screws (26) and the inlet manifold (24).

Removing the drive gear (27)
Unscrew the nut, extract the washer and remove the gear (27) and key.
Take off the pump. Remove the pipe (28) and associated seals (29) (31).

Reassembly
Clean the mating faces of the cover plate and linkage spool valve.
Ensure none of the channels are blocked.

On the internal face
Refit the pipe (28) with new seals (29)(30).
Refit the pump with a new seal (33).

Refitting the drive gear (27)
Position the key. Fit the gear, ensuring that the key is correctly engaged. Position the washer. Smear the nut with Loctite 242 or equivalent and tighten to a torque of 50 Nm. Replace the seals (23) (25). Refit the inlet manifold (24). Fit the screws (26) and tighten to a torque of 15 Nm.

On the external face
All seals must be replaced during reassembly.
Refit the unions and plugs according to the markings made during step.
Refit the 17 bar valve (16) (40-55 Nm), the pressure switch (12) (20 Nm) and the temperature switch (7) (15 - 20 Nm). Refit the linkage security valve (19).
Refit the linkage spool valve (17). Fit and tighten the screws (21) to a torque of 36-46 Nm.