The 2003-2006 Ford Expedition is built with the following suspension components:
2003-2006 Ford Expedition Air Springs (x4)- commonly referred to as air bags, a plastic and rubber bag that is fitted on top of the strut that uses pressurized air as a cushion instead of a metal coil spring to hold a vehicle off of the ground and off of its wheels. These are the number one cause of all air suspension leaks. All air springs all go bad at about the same rate. If one is leaking, the others will not be far behind. For a proper repair, all of them need to be replaced at the same time.
2003-2006 Ford Expedition Struts (x4)- a type of shock absorber; has metal tubing filled with gas-charged hydraulic fluid that is connected to the wheel of a vehicle in order to reduce the effects of vertical travel on a rough surface which controls the bounciness, and therefore comfort, of a vehicle.; the air spring assembled on top of the strut is commonly referred to as an air strut.
2003-2006 Ford Expedition Height Sensors (x4)- a linkage located near each wheel of a vehicle with any electronic suspension that, either mechanically or electronically, constantly measures the height of the vehicle, and reports this information back to the control module so that the computer can identify if changes in height need to be adjusted accordingly. The ride height sensor is a moving part, and like all moving parts, they will eventually wear out.
2003-2006 Ford Expedition Air Lines- tubes that run from a compressor (air suspension) to the air struts which carry pressurized air to the air bags components in order to adjust the height of the vehicle, respectively.
2003-2006 Ford Expedition Solenoids (x4)- usually L-shaped, these plastic components connect the electrical connection and lines of suspension components to the suspension control module on vehicles with active suspension. The solenoid regulates the air pressure for each air spring. Solenoids start to leak as they wear out causing the vehicle to sag or to lean. This will cause the ride height sensor to send a signal to activate the compressor in an attempt to inflate the air suspension and level out the vehicle. This excessive work load will eventually lead to total failure of the compressor.
2003-2006 Ford Expedition Compressor- creates/sends pressurized to active suspension components. When the air suspension starts leaking, the compressor/pump starts working harder to try to keep the system inflated. By the time air suspension leaks down completely, sitting the vehicle on its tires, the compressor will either have failed or be well on its way to full failure. Buying replacement struts and taking the time to install them only to find out the compressor still needs to be replaced can be very frustrating, time-consuming, and expensive.
2003-2006 Ford Expedition Dryer Assembly- used to keep moisture out of air lines and air springs in order to prevent freezing and internal cracking of these parts. Once air suspension starts leaking, moisture will build-up throughout the air system. Moisture damages the air suspension from the inside. The dryer will need to be replaced in order to eliminate the moisture and prevent any further damage.
2003-2006 Ford Expedition Suspension Control Module- a computer which is responsible for the operations of the air suspension system and maintaining the vehicles correct ride height.
2003-2006 Ford Expedition O-rings- Although they are the least expensive parts of the air suspension, they are responsible for maintaining the seal where all of the air lines connect. Be sure to replace the O-rings when repairing any air suspension system.