Struts or Shock Absorbers Bench Test On Vehicle

The strut dampener is basically a shock absorber which has been integrated into the strut assembly. Strut dampeners are easier to extend and retract by hand than are shock absorbers. In order to evaluate the performance of the strut dampeners, follow the procedures for on-vehicle checks and bench checking. For bench checking the strut dampeners, refer to Struts or Shock Absorbers Bench Test.

1. Check and adjust the tire pressures to the pressures shown on the Tire Placard.
2. Note the load conditions under which the vehicle is normally driven.
3. If practical, ride with the owner in order to be sure you understand the complaint before proceeding to the next step.
4. Test each strut dampener in turn by quickly pushing down, then lifting up, the corner of the bumper nearest the strut dampener being checked. Use the same amount of effort on each test.

Note the resistance on the compression and rebound.

Compare the compression and rebound with a similar vehicle having acceptable ride quality. Both struts should provide the same feeling of resistance.

1. Check all mountings for proper torque. A loose mounting will cause a noise.
2. If all mountings are intact, bounce the vehicle in order to isolate the suspected unit. Any sound other than hissing is abnormal.

2.1.	Test each strut dampener in turn by quickly pushing down, then lifting up, the corner of the bumper nearest the strut dampener being checked. Use the same amount of effort on each test.

2.2.	Note the resistance on the compression and rebound.

2.3.	Compare the compression and rebound with a similar vehicle having acceptable ride quality. Both struts should provide the same feeling of resistance.

1. Fully extend the strut dampener (wheels unsupported) in order to expose the seal cover area for inspection.
2. Look for signs of leaks in the seal cover area.
3. A slight trace of fluid is NOT cause for replacement; the seal permits some seepage to lubricate the piston rod. A built in fluid reserve allows for slight seepage.
4. Fluid around the seal cover and an excessive amount of fluid on the strut indicates a leaking strut dampener. Replace all leaking strut dampeners.

Struts or Shock Absorbers Bench Test Off Vehicle

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

Bench Test

1. Clamp the strut in a vise with the strut damper upright, top end up. Do not clamp on the reservoir tube.
2. Pump the strut damper by hand at various rates of speed. Note the resistance.
3. Rebound resistance normally is stronger than compression resistance by about 2 to 1. The resistance should be smooth and constant for each stroking rate.
4. Compare the strut damper under inspection with a strut damper known to be good.
5. 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

•	Fluid leakage