Question 1

When air suspension needs servicing

Accepted Answer

Air suspension has become common on premium vehicles and gives the driver the ability to adjust ride height and damping. Mercedes-Benz, BMW, Audi, Land Rover and Volvo all use it, particularly on their SUVs, and on some cars it's also fitted to saloons. The system is complex: a compressor generates compressed air, a valve block directs the air to the right location, and each wheel has its own air spring replacing the conventional coil spring.

The most common fault is an air spring splitting. A long-serving air spring gradually "loses" pressure overnight – in the morning the car has sagged on one side and the compressor has to run for a long time when you start the vehicle. Ageing of the rubber sleeve is behind this; the rubber becomes brittle under UV and frost and develops porosity.

The second frequent failure is the compressor itself. It contains an electric motor that, under normal use, lasts 8–10 years, but if the system has leaks the compressor has to cycle far more often and wears out much sooner. In the worst cases the compressor's fuse blows or the motor burns out internally, the system stops working entirely – the car sinks onto its bump-stops and won't rise.

Question 2

How air suspension is repaired

Accepted Answer

Repair always starts with reading fault codes on the diagnostic tool and measuring system pressures. From this we can see whether the fault is a leak, the compressor or the control valve. Next we carry out a leak test: the car is raised to its maximum height, the system is locked and pressure is measured at each corner every 10 minutes. Leaks are localised with soapy water – every fitting, valve and air spring is checked in turn.

Replacing an individual air spring is done in the same way as a conventional coil spring – the relevant corner is stripped down and the new unit fitted. Extra care is needed when fitting air springs to make sure the protective gaiter isn't pinched – a pinched gaiter would cause the fault to return within a few months. A set pressure is used when charging the new spring so that the system recognises it correctly.

The compressor is usually replaced from underneath the boot floor, where it sits in a protective housing. The air lines are cleaned before the new compressor is fitted so that any dirt or moisture residues – which would have caused the original failure – are removed. Finally a calibration drive is carried out on the diagnostic tool: the system learns the new height calibration and clears all fault codes.

Question 3

Why does air suspension fail?

Accepted Answer

Air suspension is itself a reliable system, but its individual components are vulnerable in Finnish conditions. Rubber air springs embrittle under the combined effect of frost and UV, and their service life can be shorter here than in warmer countries, typically 8–12 years. Moisture build-up inside the compressor is another frequent issue: every time the compressor runs it draws in air from the atmosphere, and that air always carries some humidity. If the dryer cartridge has aged, moisture accumulates in the system, freezes in winter and causes premature valve failures. A third cause is heavy, regular loading – every load extends the stroke of the springs and wears the sleeves faster. It's worth having the air suspension checked before winter on any vehicle where the system is more than 8 years old.

Air Suspension Repair in Vantaa