Checking Level Control Pressure Oil Pump

NOTE: Numbers in parentheses ( ) indicate a component or tool in the associated illustration.

REMOVAL

WARNING
^ Risk of injury to the eyes and other parts of the body due to hydraulic oil spraying out under high pressure.
^ Wear protective clothing and safety glasses. Technician Safety Information


NOTE:
^ Before starting work on the hydraulic system, depressurize the system.
^ Seal open connections with blind plugs.
^ Refer to general notes for working on vehicles with level control/ADS. Vehicle Damage Warnings

1. Empty pressure oil system, refer to Emptying And Filling Pressure Oil System
2. Connect tester to level controller (3), refer to Connecting Pressure Gauge to Rear Axle Oil Distributor Fitting
3. Pour oil into oil reservoir (2)
- For testing, increase the quantity of oil to approx. 0.5 liters above the "max." marking (a) on the oil dipstick (2a).
4. Disconnect return line (T) at at reservoir (2)
- Connect oil drain hose to the return line (T) and guide into oil reservoir (2)
- To measure the delivery rate of the pressure oil pump.
- Pay attention to secure hose routing.
- When the pressure relief valve in the level controller opens, the oil pressure in the return line increases to approx. 2 bar.

WARNING
^ Risk accident due to the vehicle starting off automatically when engine is running.
^ Risk of injury due to bruising or burns when intervening while starting the engine or when the engine is running.
- Only wear the appropriate clothing for working on the vehicle.

5. Start engine and allow to idle.
6. Set level controller lever (3a) to "Fill" position (F).
7. Checking delivery pressure of pressure oil pump as follows:
- Only carry out the test briefly due to the high pressures.
- The delivery pressure of the pressure oil pump is limited by the pressure relief valve in the level controller.
- The opening of the pressure relief valve is audible due to whistling noises.
- Opening pressure of pressure relief valve: 120-153 bar
- If the opening pressure of the pressure relief valve is clearly not achieved and delivery rate at idle speed
- Replace pressure oil pump/tandem pump
- If the opening pressure of pressure relief valve is exceeded
- Check level controller on the rear axle

8. Checking delivery rate of pressure oil pump as follows:
- Guide hose piece on the return line (T) into a measuring vessel
- Ensure that there is sufficient oil in the oil reservoir.
- The pump must not ingest air under any circumstances it the delivery rate of greater than 0.2 liters per minute is not achieved.
- Replace pressure oil pump/tandem pump if the delivery rate is not reached
9. Switch off engine
10. Set level controller lever to center position
11. Connect line (T) to oil reservoir (2)
12. Disconnect tester at level controller

WARNING: Danger due to oil spraying out

13. Fill pressure oil system