SACHS

  • Some valuable tips on how workshops can correctly install shock absorbers are included below. Due to the many different types of shock absorber, we can only provide you with a few basic instructions on replacing shock absorbers here.

    WARNING:Risk of serious injury caused by the sudden release of springs. Always use a suitable spring compressor.

     
    Removing the sensor cable
    Removing the sensor cable

    Tips for the front axle

    • If you want to replace vibration dampers, use a suitable tool (e.g. a transmission jack) to support the wheel suspension before removing the shock absorbers.
    • Replacing passenger car shock absorbers on a McPherson spring strut requires, where appropriate, that the cables are detached from the wheel speed sensors (also known as ABS sensors) and electrical lining wear indicator, and the brake hose is detached from the corresponding brackets. (see illustration)
    • Loosen and remove all mounting bolts, and remove the shock absorber and/or spring strut. If you also remove a spring strut, you must observe the installation instructions and safety regulations from the manufacturer.
    • For the assembly and installation, replace all of the mounting bolts and install the supplied accessory. Observe the torque that is specified by the vehicle manufacturer for the mounting bolts.Secure any cables that may have been detached from the ABS sensors (wheel speed sensors) and electrical lining wear indicator before replacing the shock absorber, as well as the brake hose, back into the corresponding brackets.
     
    Marking on the rear axle
    Marking on the rear axle

    Rear axle

    • Before the removal, use a suitable tool to support the chassis (e.g. a transmission jack).
    • If required, remove any trims from the vehicle interior in order to reach the damper’s upper mounting bolts.
    • Loosen and remove all mounting bolts, and remove the shock absorber.
    • For the installation, replace all of the mounting bolts and install the supplied accessory. Observe any existing markings for the installation and the torque that is specified by the vehicle manufacturer for the mounting bolts (see illustration).

Final notes

  • In order to guarantee safe vehicle handling, always replace both shock absorbers on an axle!
  • After replacing the shock absorbers, carry out an axle alignment.
  • Then carry out a test drive in order to check that they are working correctly.

SACHS useful tip:

Installing shocks and dampers free from distortion

Improper assembly or accidents can lead to a distortion of shocks and dampers and later to serious component damage. ZF Aftermarket describes what to pay attention to during inspection and installation.

Distortion can severely reduce the service life of shocks and dampers. ZF Aftermarket explains the causes as well as the effects on the chassis component technology and suggests preventive solutions.

 
Piston rod jammed

Accidents and installation as most frequent sources of error

ZF Aftermarket names two main reasons for shock absorber/damper distortion: Firstly, even minor accidents may lead to the shocks’ and dampers’ mounting points being displaced so that they are no longer flush. Frequently, the piston rod is also bent in the process. Secondly, lack of care during installation is a frequent cause. When the axle is still suspended, the shocks and dampers must not be tightened firmly – the reason: Once the vehicle stands on the ground again, the mounting points are not properly aligned anymore either. The serious impact on the inner workings of the shock or damper is identical in both cases.

 
Piston rod worn through

Performance loss due to worn-down seals

Due to the distortions, one side of the chromium plating on the piston rod surface presses against the guide and sealing unit with each stroke – and is ultimately worn through. Thisresults in strong wear on the seals and piston rod guide, mostly ending in a loss of oil and, thus, performance of the shock or damper.

 
Distorted absorbers

Preventing distorted shocks or dampers and torn out pin joints

To prevent the described distortions and defects, workshops should follow one simple rule: As a basic principle, shocks or dampers may only be tightened once the vehicle stands on its wheels – or when the wheels are pressed upwards with tools such as hydraulic jacks. Also, the specified tightening torque must be observed.

Last but not least, shocks and dampers installed under tension or a fastening nut tightened too firmly may lead to the pin joint tearing out. To prevent material overexpansion due to excessive tightening torques, it must be observed that, as a rule, no impact wrenches must be used when performing this work.

If these ZF Aftermarket tips are observed, shocks and dampers will function safely and reliably in the long term. This provides peace of mind for workshop customers too.

SACHS useful tip:

Shocks and dampers leak.

Causes

Although a shock absorber or damper may appear to have a leak, this may not in fact be the case. A certain amount of “perspiration” is normal, and even necessary to lubricate the piston rod seal.

Never diagnose shocks and dampers after the vehicle has been driven in the rain – they should be dry.

Therefore:

  • Feel the shock absorber/damper with dry fingers. If your fingers remain dry, the shock absorber/damper is not leaking.
  • If you are still not sure, wipe off the shock absorber/damper. Check again a few days later!
 
Oil mist residue on shocks and dampers
Oil mist on shocks and dampers

Oil mist residue on shocks and dampers

Cause:

  • During every stroke, the piston rod carries a very small amount of oil from the working cylinder to lubricate the seal.

Consequence:

  • If the shock absorber/damper was bone-dry, residue from this oil mist will be visible.

Comment:

This is not a malfunction. Following extended periods of use, oil mist residue may be visible on around 1/3 of the container tube.

 
Shocks and dampers show clear traces of oil
Traces of oil on shock absorber

Shocks and dampers show clear traces of oil

Cause:

  • The piston rod seals are worn out due to:
    • Long use
    • Severe operational demands
    • Sand or road dirt

Consequence:

  • Oil loss, and thus lower damping forces
 
Underbody sealant on shocks and dampers
Underbody sealant on shock absorber

Underbody sealant on shocks and dampers

Cause:

  • Underbody sealant or corrosion-preventive wax collects on the shocks and dampers.

Consequence:

  • It appears that oil is leaking.
  • Heat dissipates more slowly.

Comment:

These substances do not belong on the shocks and dampers, so remove them! Accumulated road dirt is also often wrongly diagnosed as leakage.

 
Chrome coating on piston rod worn out
Chrome coating on piston rod worn out

Chrome coating on piston rod worn out

Cause:

  • Strong distortion of shock absorber during installation
  • Misaligned attachment points.

Consequence:

  • Wear on seal and piston rod guide, leading to oil loss and reduced performance

Comment:

Always tighten the shocks and dampers only after the vehicle is standing on its wheels.

 
Piston rod damaged
Piston rod damaged

Piston rod damaged

Cause:

  • The piston rod was gripped with pliers during installation, which damaged its surface.

Consequence:

  • A rough piston rod surface causes the seal to tear, leading to oil loss and reduced performance.

Comment:

Use a special tool to hold the piston rod.