Pictured above is the cross section of a Bilstein B4 air suspension module
What is an Air Suspension?
Air suspension is a type of vehicle suspension that is powered by an engine driven compressor. The compressor pumps air into flexible bellows (what we also call, air springs). These air-springs are usually made up of textile-reinforced rubber. The air pumped in to the air-springs by the compressor causes the springs to inflate, raising the chassis from the axle.
William W. Humphreys, an American, patented the idea of an Air Suspension way back in 1901. Ever since numerous autmakers and technical organizations have tweaked the design and applied it to their vehicles in a variety of ways. It even played a vital role in WW2 when the US developed it to be used in their military aircrafts and heavy trucks. They used it primarly for height adjustment and level control in these vehicles.
Over the course of a decade since its inception, major automakers such as Citroen, Mercedes-Benz, GM, Ford, VW, took this idea and engineered it in ways that improved the performance of their road cars. Couple of notable mentions include the iconic Citroen DS, Cadillac Eldorado Brougham, Mercedes-Benz 300SE, Range Rover 3, Audi Q5 and so on..
Cadillac Eldorado Brougham
How Does It Work?
Mercedes-Benz claims that using air suspension is like “Riding on a cushion of air”. And I agree. A car equipped with air suspension is far more comfortable to drive on uneven roads then those with traditional metal springs and struts. Nowadays, most luxury car manufacturers use air suspension assemblies of varying designs, in their production cars. Its extensively used in Mercedes-Benz, Audi’s, Range Rovers and other, mostly premium, cars.
The key elements that make up an Air Suspension assembly are –
- Air Compressor – responsible for supplying compressed air to the air-springs
- Air-Springs/Bellows – these inflate when filled with air provide the “cushioning effect”.
- Pneumatic lines – supplies air from the compressor to the air-springs
- Solenoid Valve – controls the air supply from the compressor to the air-springs.
The air compressor compresses and sends air to the air-springs via the pneumatic lines. Depending on the load and the type of surface the car is driving over, the solenoid valve adjusts the air sent to each of the springs providing a seamless, smooth ride.
Certain vehicles such as the Mercedes-Benz GL, Range Rover 3 feature height adjustable suspension setup. The driver is able to adjust the height of the car, using a knob, depending on the type of terrain he’s driving over. A raised suspension set up is preferable for off-roading while lowered suspension set up makes high speed driving much more enjoyable.
Common Air Suspension Problems
- Air-Spring failure is caused by wet rust, due to old age, or moisture within the air system that damages it from the inside. Also, punctures may be caused from debris on the road.
- Air Line Failure is a failure of the pneumatic lines which connects the different elements of the air suspension system
- Compressor Failure is caused as a result of leaking or damaged air-springs. The compressor runs overtime trying to maintain air pressure and eventually burns out.
Pictured above: BMW X6 and GL-350 with faulty air suspension
Air Suspension Replacements & Repairs – Simplified
The first sign of trouble would be a warning on your cars heads-up display. If you face any issues with your cars air suspension, call Cartisan! We have well trained technicians who are proficient in air suspension system repairs and replacements!
Written by Vfawke. Photographs by Cartisan Service Team.
Also published on Medium.