Self-levelling suspension –shock absorbers and –pressure reservoirs 

are the main components of the levelling system and often the major source of error - these parts wear out more often. Unfortunately these spare parts are very expensive and in some cases even not available.

The wearing out of levelling suspension is a successive worsening process, often not recognized by the driver.

For a more detailed explanation of Audi self-levelling suspension: click

The most common fault symptoms are:

Vehicles rear is standing high, reduced or not springy (hard hopping). Cause: Pressure reservoirs have too little nitrogen gas pressure.     

Rear is standing high and not springy, height is not adjustable. Cause: Pressure reservoirs have no nitrogen gas - sometimes associated with a damaged height regulation valve.

Rear's height is different at LH and RH side. Cause: Pressure reservoirs with very different nitrogen load; one shock absorber is leaking excessively 

Oil leak at shock. Cause: Blown shock absorber seals (often caused by less nitrogen gas)

Rear is deepening when engine is cut off. Cause: Leaking shock seals ; leaking pressure hose; leaking regulation valve (often caused by less nitrogen gas).