Air suspension earns its keep every day — protecting cargo, axles and drivers — and mostly asks only for air-system health in return. When it misbehaves, the symptoms are wonderfully specific: trucks that kneel overnight, lean on one corner, or bounce like a ship in swell.
Reading the symptoms
- Sinks overnight: a leak — bag, line, fitting or a levelling valve bleeding down. Soapy water finds it.
- Leans one way: a failed bag or a levelling valve stuck on one circuit; on ECAS systems, a drifted height sensor.
- Constant compressor cycling: the system is feeding a leak; find it before it takes the air dryer with it.
- Harsh ride or bounce: shocks do the damping — bags only carry. Worn dampers show up in tyre cupping too, as our tyre wear guide notes.
ECAS: the electronic layer
Electronically controlled air suspension replaces pure mechanics with height sensors, a control unit and solenoid valve blocks — adding features (kneeling, docking heights, axle-load management) and new failure modes. Implausible-height faults, dead solenoid coils and calibration drift after component changes are the classics. After replacing bags, sensors or valve blocks, calibrate — skipping it is how a repaired truck comes back on the hook. Vaden’s ECAS solenoid valve guide covers the control side well.
Bag inspection discipline
At every service: look for chafing against brackets and lines, cracking in the rubber folds, and corrosion on piston seats. A bag costs little; the consequential damage of one letting go at speed — brake lines, wiring, cargo shift — does not.
General information for professional operators. Always follow the vehicle manufacturer’s procedures and local regulations.