Tractor hydraulic system - Oil decontamination

The correct operation and performance of the hydraulics system is closely linked to the use of clean transmission oil. When maintenance is carried out on the gearbox / axle assembly (e.g. brake or transmission repairs) this contaminates virtually the whole hydraulic circuit. It is therefore essential to carry out a decontamination operation after repairs in order to avoid the rapid deterioration of other components in the circuit caused by the movement of particles carried by the oil. The contamination of oil can result in:
- seizure or leaks in the steering spool valve (Orbitrol)
- seizure of the spool valves in the solenoid valves
- excessive wear in the hydraulic pump(s).
The aim of oil decontamination is to restore the hydraulic circuit to a state of cleanliness higher than that before the repair operation. The particles that cause the greatest damage are not the largest ones, for these are rapidly caught in the filter, it is the repeated circulation of small non-filtered particles that has the greatest abrasive effect.

Decontamination procedure

Special point
- The decontamination is carried out in two distinct phases.

The static phase
- This takes place immediately after the repair operation, without moving the tractor.
- Check that the oil has been replaced after the repair operation.
- During this phase, no low-pressure components should be activated.
- The decontamination is carried out by circulating the contaminated oil to the housing return through filter elements in order to rapidly remove any particles suspended in the oil.

Preparation of the tractor 
The equipment used for oil decontamination is two hose pipes of a suitable length fitted with a female diagnostics connector, on one of the ends.

Disconnect the temperature switch (3) (Heavy Duty transmission) and ground it to earth in order to neutralise its action.
Connect the female diagnostics connector of each hose pipe on the male connectors (1) (2) of the lowpressure circuit. These connectors are respectively located on the right-hand side hydraulic cover, on the clutch valve or the Reverse Shuttle hydraulic control unit, depending on the version.
Fasten the other end of the hose pipes without connectors to the return port R.

- The oil temperature must be above 10° C to avoid the opening of the by-pass. Start the engine and run it at 1200 rpm.
Allow the engine to run for 15 minutes minimum in order to filter out the particles in the oil. Check that the clogging indicator lamp on the dashboard does not light during the decontamination operation. If this does happen, replace the 15-micron filter element and check or change the suction strainer.
After having let the engine run for 15 minutes, stop the engine and replace the 15-micron filter by a 6-micron filter. Procure a hose pipe of appropriate strength, fitted at each end with a male quick-disconnect coupling for connection to the auxiliary spool valves.

Connect the connectors of the flexible to ports A and B of the same spool valve. Start the engine and run it at 1200 rpm.
While the engine is running, turn the knurled knob of the spool valve to maximum flow and alternate the direction of oil circulation in the spool valve for approximately 5 minutes using the control lever. Repeat the operation on the two or three other spool valves (depending on options).
- If the clogging indicator lamp lights on the dashboard, replace the 6-micron filter element by another of the same type.

Dynamic phase
- Contrary to the static phase, the dynamic phase uses all the hydraulic functions of the tractor for 15 minutes with the engine running:
- lift control
- steering
- power take off
- brakes
- etc.

Preparation of the tractor
Remove all the hose pipes used during the static phase.

- During decontamination, carefully monitor the dashboard clogging indicator. If necessary, immediately replace the 6-micron filter and the suction strainer.
Raise and lower the lift arm over the entire travel of the rams and carry out a rapid alternating raise and lower cycle. Turn the steering wheel to full lock in both directions several times. Declutch and allow the clutch in and out 5 or 6 times using the full travel of the pedal (tractors with Heavy Duty transmission). Repeat the same operation again more quickly. Press and release each of the unlatched brake pedals several times. Repeat the same operation more quickly. Slowly press and release the latched pedals several times. Repeat the same operation again more quickly.
Activate the Dynashift control, located on the left beneath the steering wheel, moving it from A to D and vice versa several times. Operate and halt the power take off 4 or 5 times, one after another. Reconnect the temperature switch.

Carry out a road test the tractor using various engine speeds, changing up and down through the ratios for approximately 15 minutes.
When the road test is completed, let the engine run at 1200 rpm for approximately 15 minutes with the tractor stationary, in order to eliminate any remaining particles in the circuit.

Preparing the tractor for service
When all these operations have been completed, prepare the tractor for service by replacing the suction strainer and the 6-micron filter used for decontamination with a new and original spare parts suction strainer and 15-micron filter, as referenced in the Spare Parts catalogue.


Parts list 
(1) Decontamination connectors (low pressure)
(2) Decontamination connector on clutch valve or Power shuttle hydraulic control unit (Heavy Duty transmission)
(3) Temperature switch (Heavy Duty transmission)
(4) Oil decontamination replaceable oil filter element (6 micron)
(5) Clogging indicator
A : Pressure Load ed - Mechanical reverse shuttle version
B : Reverse shuttle version

Parts list 
(1) Decontamination connectors (low pressure)
(4) Oil decontamination replaceable oil filter element (6 micron)
(5) Clogging indicator