Symptom Related Diagnostic Procedures

WM 430149 Troubleshooting the levelling system

General warning notes

Safety instructions-> 4X00IN03 Safety notes and information when repairing the chassis 4X00IN03 Safety Notes and Information When Repairing the Running Gear

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 off-road level using the rocker switch (selector switch) for the levelling system (observe display in the instrument cluster). Then lower the vehicle to normal level again.

- Switch off the engine, ignition off.

- Pull off connector on the levelling system control unit to prevent a levelling system readjustment. -> 43161900 Removing and installing levelling system control unit 43161900 Removing and Installing Level Control Module

- Measure the vehicle height -dimension X- at all four wheels on the vehicle. => Vehicle height at front axle -dimension X- (from wing to centre of wheel) => see figure





Vehicle height at front axle -dimension X- (from wing to centre of wheel)

- Measure the vehicle height -dimension X- => Vehicle height at front axle -dimension X- (from wing to centre of wheel) => see figure again after two hours and compare it with the first measurement.





Vehicle height at rear axle -dimension X- (from wing to centre of wheel)

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 damper, the relevant air line and the residual pressure retaining valve 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 4 mm after 24 hours.

The following components must also be checked:
- Air line connections
- Residual pressure retaining valve
- Air-spring damper

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 damper 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 solenoid valve block, it must be replaced.

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

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