Struts or Shock Absorbers Bench Test Off Vehicle
Air-Adjustable (ELC) Strut Damper
Stroke all air-adjustable strut dampers before attempting a bench check.
When stored horizontally, such as new units in stock, an air pocket may develop
in the pressure chamber. This pocket can also form when an air-adjustable
strut is off the vehicle if it is not continuously held with the top end
up.
Perform the following procedure in order to remove air from the pressure
chamber:
Purge
- Extend in vertical position, top end up.
- Collapse in vertical position, top end down.
- Repeat this procedure five (5) times in order
to verify that the air is purged from the pressure chamber.
Bench Test
- Clamp the strut in a vise with the strut damper upright, top end
up. Do not clamp on the reservoir tube.
- Pump the strut damper by hand at various rates of speed. Note
the resistance.
- Rebound resistance normally is stronger than compression resistance
by about 2 to 1. The resistance should be smooth and constant for each stroking
rate.
- Compare the strut damper under inspection with a strut damper
known to be good.
- It is normal to hear a hissing noise. The following symptoms are
abnormal and are reason for replacement.
| • | A skip or lag at reversal near mid-stroke |
| • | A seize (except at either extreme end of travel) |
| • | A noise (such as a grunt or squeal) after completing one full
stroke in both directions |
| • | A clicking noise at fast reversal |
