Procedure For Checking The Levelling System
- Perform check under the following 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.
Information
Do not get into or out of the vehicle while adjusting the vehicle to normal level and after adjusting it to normal level (do not change the position of doors and flaps). This can give false alignment results.
Perform check under the following 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.
- 1.1 Only for vehicles with air suspension:
Switch to Normal Level and deactivate the levelling system.
- 1.1.1 Switch on the ignition.
- 1.1.2 Switch to Normal Level. Select DRIVE > Air suspension level > Middle in the PCM.
- 1.1.3 Deactivating the levelling system: Select CAR > CONTROL > Vehicle > Chassis > Jack mode in the PCM.
- 1.2 Compress vehicle at front and rear axles by approximately 25 mm 2-3 times and allow it to spring back freely.
- 1.3 > VAS 6918 - Quick-Clamping Unit
must be fitted on the wheels.
- 1.3.1 Remove hub cap using > 9229/1 - pull-off hook .
- 1.3.2 Mounting surfaces for the quick-clamping holders on the wheels and the adapter surfaces must be clean and flat.
- 1.3.3 Position quick-clamping unit (with the claws first) in the centre of the rim and tighten it by turning the retainer (clockwise) in the rim.
- 1.4 Determine the actual value for the height of the vehicle body at the measuring points.
Dimension X = upper edge of measured-value pickup to lower edge of wing, shown as an example
- 1.4.1 When determining the height of the vehicle body, the height is measured from the lower edge of the wing to the upper edge of the measured-value pickup, dimension X.
- 1.4.2 To this measured dimension -X-
, add the radius of the measured-value pickup 32.5 mm.
Sample calculation:
Measured dimension X = 382 mm; measured-value pickup radius = 32.5 mm
X + measured-value pickup radius = vehicle body height
382 mm + 32.5 mm = 414.5 mm
- 1.5 Measure the vehicle height (See
) again after two hours and compare it with the first measurement.
Dimensions and tolerances can be taken from the prescribed vehicle height for vehicles with air suspension.
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 following components must also be checked:
- Air line connections
- Air-spring strut/air spring
- Valve unit
If the vibration dampers are faulty, 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.
- 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.