Expedition 2WD V8-281 4.6L VIN W EFI (1997)
Air Spring: Description and Operation
Four Wheel Air Suspension
Rear Air Spring
The 4WAS vehicles use a pneumatic spring in the rear. The pneumatic spring is essentially a column of gas confined in a container, utilizing the pressure
of the gas as the force medium of the spring. The ability of the gas to compress provides the desired elasticity for the spring. The air suspension system
regulates the pressure in each air spring by compressing and venting system air. Increasing air pressure (compressing) raises the vehicle; decreasing air
pressure (venting) lowers the vehicle. Vehicle height is maintained by the addition and removal of air in each air spring through an integral solenoid
assembled to the upper spring cap and energized through the control module command.
The air spring assemblies are mounted between the axle spring seats and the frame upper spring seats.
The air springs replace the conventional coil springs.
Front Air Shock Absorbers
There are different shock absorbers used for 4WAS air suspension system vehicles. 4WAS uses a conventional air shock. Enclosed in each shock
absorber is an air spring. To replace a faulty shock absorber, replace the shock absorber as a unit.
The air spring integrated into each air shock is capable of independently raising and lowering each corner of the vehicle based upon the pressure and
volume of air supplied. The air suspension system regulates the pressure in each air shock by compressing and venting system air. Increasing air pressure
(compressing) raises the vehicle and increases the total spring rate (spring effect of the air shock plus the front torsion bar) of the wheel being modified.
Conversely, decreasing air pressure (venting) lowers the vehicle and effective spring rate. Vehicle height is then maintained by the addition and removal
of air in each air shock.