Automotive Shock Absorber Maintenance and Repair

Inspection
To rapidly dampen vibrations between the frame and the body and to improve ride smoothness and comfort, automotive suspension systems are typically equipped with shock absorbers; dual-acting tubular shock absorbers are the most widely used type.

Shock absorbers are components prone to wear during vehicle operation. Their performance directly affects vehicle stability and the service life of other mechanical parts; therefore, they should be maintained in good working condition. The following methods can be used to assess their performance.

Shock absorber inspection includes performance testing, durability testing, and dual-excitation testing.
Tests such as indicator diagram (force-displacement) tests, friction tests, and temperature characteristic tests are conducted on various types of shock absorbers.

Repair
Once a shock absorber is identified as faulty or failed, first inspect it for oil leaks or traces of old leakage.
Check for cracked or damaged oil seals and gaskets or loose reservoir cylinder cap nuts. If oil seals or gaskets have failed, replace them with new ones. If the leak persists, remove the shock absorber and check for binding or inconsistent resistance. Further inspect the clearance between the piston and cylinder, check the piston rod for bending, and examine the surfaces of the piston rod and cylinder for scratches or scoring marks.

If there is no oil leakage, inspect the connecting pins, rods, mounting holes, and rubber bushings for damage, broken welds, cracks, or detachment. If these components are intact, disassemble the shock absorber to check the fit clearance between the piston and cylinder, inspect the cylinder for scoring, and verify valve sealing integrity (ensuring a tight fit between the valve disc and seat). Also, check the extension spring for excessive softness or breakage. Repair by refinishing or replacing parts as necessary.

Additionally, shock absorbers may malfunction by producing noise during actual operation. This is primarily caused by the shock absorber colliding with leaf springs, the vehicle frame, or the axle; damaged or detached rubber cushions; deformation of the dust cover; or insufficient fluid levels. The specific cause should be identified and rectified.

After inspection and repair, shock absorbers should undergo performance testing on a specialized test bench. With a stroke of 100 ± 1 mm, the resistance forces during the extension and compression strokes must meet specified standards.

If testing equipment is unavailable, an empirical method can be used: insert an iron rod through the lower mounting eye of the shock absorber, stand on both ends of the rod with your feet, and grasp the upper mounting eye with both hands to pull it up and down 2 to 4 times. If there is significant resistance when pulling upward but little effort required when pushing downward-and if the resistance has been restored compared to its pre-repair state without any sensation of "dead travel" (free play)-then the shock absorber is considered to be functioning normally.