Air Suspension Repair and Service
Air suspension is a shock absorber with a pneumatic baloon installed on it (instead of a spring) and performs the function of maintaining a certain level of the vehicle body relative to the roadway. This is made possible by changing the pressure in the air suspension.
A shock absorber is a device used to dampen vibrations, as well to absorb shocks and hits of moving parts (wheels and suspension), and the vehicle body itself.
A back pressure valve is usually installed on closed-type air suspension supports in case of a broken pneumatic line (pipe) or any other leakage so that all air does not come out of the air suspension cylinder. Otherwise, all the air will come out, and the rubber sleeve will bend, and it will simply tear it off with the details of the air suspension itself.
But in this case, there will be 5-6 atmospheres of air in the air suspension, and it will work in the normal mode. The pillow will still get on the bump stops, but the sleeve will be filled with air, so it will not tear. But if leakwill happen in the cylinder, the valve will not save. Although, in practise happened that the valves on the front cylinders of the Tuareg fell off, the air suspension was chewed, but whole, without a break.
In receivers of different car models there can be different pressure. In the rear air suspension one pressure, in the front – pressure will be higher. On average, in the receiver of most cars, the pressure ranges from 12 to 13 atmospheres. For example, in Range Rover Discovery car, the pressure can reach 18-20 atmospheres. If the air suspension compressor is not capable of injecting pressure over 17 atmospheres, the system shows an insufficient pressure signal. There were cases when the compressor did not pump up to 20 atmospheres, but only 18 were injected. This was no longer enough, and the system signaled an error until a pressure of 20 atmospheres was provided.
During the long trip, the car completely fell on the bump stops from all sides. The driver slowly drove by himself to the nearest service station. Diagnostics revealed that the height sensor had failed. Water got into the sensor, so it gave out incorrect signals, the «brains» saw this problem and lowered the air suspension and switched it to emergency mode.
Replacement of sensor has solved this problem. If a similar situation happens while driving, either slowly continue to drive on the bump stops to the service station or call a tow truck. For example, the Audi Q7, Porsche Cayenne and Volkswagen Touareg air suspensions are high, so even when the car lies on the bump stops, the wheels do not reach the arches. The ride will be tough, like on a cart, but possible.
In the case, with a Mercedes W220 car, it is better to use a tow truck, because at the slightest turn of the steering wheel, the wheels will cling to the arch. You can go on a straight road, but the steering wheel can be turned to a small angle. In this case, it is suggested to turn off the compressor. This can be done by switching the air suspension to the jack mode or disabling the relay/compressor fuse, but everything will depend on the specific vehicle.
There is a leak in the air suspension system, you need to look for it.