Symptom Related Diagnostic Procedures

WM 430149 Troubleshooting the levelling system

General warning notes

Information

Troubleshooting

Component arrangement - air suspension-> 4300IN Component arrangement - air suspension
1. Troubleshooting air-spring dampers and the levelling system































2. Perform the following check under these conditions:

- The vehicle must be standing on a level surface.
- The vehicle must be cold and must not be moved during the check.
- The room temperature should be between 10°C and 30°C and must not fluctuate to any great extent.

- Start the engine.

- Switch the vehicle to the high level using the high-level setting button (observe display in the instrument cluster). Then lower the vehicle to normal level again.

- Switch off the engine, ignition off.

- Switch off system. To do this, press and hold high-level setting button for at least 10 s.

- Measure the vehicle height -dimension X- at all four wheels on the vehicle. => see figure => see figure





Dimension X = centre of wheel to lower edge of wing (rear axle shown)

- Measure the vehicle height -dimension X- => see figure => see figure again after two hours and compare it with the first measurement.





Dimension X = centre of wheel to lower edge of wing (rear axle shown)

If the vehicle is lying at an angle, there is a leak at the wheel suspension with the greatest difference between the first and second measurement.

Use commercially available leak detection spray to check the affected air-spring strut/air spring and the relevant air line one after the other.

If there is no difference after two hours, the vehicle height must be measured again after 24 hours. The difference must not be more than 5 mm after 24 hours.

The following components must also be checked:
- Air line connections
- Air-spring strut/air spring
- Valve unit

If the vibration dampers are defective, oil from the vibration damper may have entered the air supply system. To ensure that the air spring system works perfectly, it is absolutely essential that you clean the system after a fault is found and replace other components.
3. Procedure for repairing the air spring system after a fault is found on the vibration dampers:

- Screw off the affected line on the air-spring strut/air spring and solenoid valve block.

- Blow out the line several times until it is clean using compressed air by introducing the compressed air at the end of the line at the solenoid valve block.

- Check for traces of vibration damper oil in the solenoid valve block.

- If vibration damper oil has contaminated the valve unit, it must be replaced.

- Check the internal line from the compressor to the solenoid valve block.

- If there is oil in the line between the compressor and the pressure accumulator, the line and the pressure accumulator must be replaced.

If there is oil in the internal line, the compressor must be replaced.