Audi A4: Shock Absorber Leaks
Vehicles with Coil Springs
Shock absorbers are frequently rejected and replaced because
of leaks. Examinations on the test stand and on the vehicle have
shown that the replacement of a large number of rejected shock
absorbers was not justified.
Slight leaking of oil ("sweating") at piston rod seal is no
reason to replace a shock absorber. A shock absorber damp with
oil is OK under the following circumstances:
Note
Minor oil excretion is an advantage, since the piston rod
oil seal gets lubricated, which thus increases service life.
This applies to shock absorbers on the front and rear axles.
- Oil leakage (shaded in illustration
-arrow-) is visible, but dull, matte and possibly dry due
to dust.
- One-sided oil or dirt film formation, no dripping.
A shock absorber is not OK under the following conditions:
- Dripping -arrow-, completely
coated with oil film
- A wet oil film that runs down the pipe indicates a leaky
shock absorber. A replacement is required in this instance.
Shock Absorbers, Checking when Removed
Defective shock absorbers are noticeable when driving due to
loud rumbling noises - a result of wheel hopping - especially on
poor stretches of road. Moreover, they can be recognized by a
large loss of oil.
Note
Shock absorbers are maintenance-free, shock absorber oil
cannot be filled.
A removed shock absorber can be checked by hand as follows:
- Push the shock absorber together by hand.
- The piston rod must move with even resistance throughout the
entire stroke and without jerking.
- Release the piston rod.
- For shock absorbers with sufficient gas pressure, the piston
rod returns automatically to its starting position.
Note
- If this is not the case, the shock absorber does not
necessarily need to be replaced. As long as there is not a large
loss of oil, the effectiveness corresponds to that of a standard
shock absorber.
- The damping function is also completely available without
gas pressure, as long as there is no large loss of oil. However,
this can increase the noise level.
Shock Absorbers, Checking on Shock Tester
Shock absorbers can be checked while installed using the
shock tester (shock absorber testing device). The damping effect
can be evaluated based on the dial reading or printout.
Special tools and workshop equipment required
- Maha Shock Absorber Tester -VAS1990S-
- Suspension Strut Test Bed -VAS6636-
- Suspension Strut Test Bed -VAS6640-
Test Requirements
- Temperature +10 to 40 ºC (+50 to 104 ºF).
- Driver must be in vehicle.
- Tire pressure OK
- Drive vehicle straight onto center of wheel contact plates.
- Front wheels in straight position.
- Mechanical parking brake not engaged, foot brake not
pressed.
Threshold
Shock absorber condition can only be judged as follows:
- Sufficient damping effect
or
- Insufficient damping effect
Note
- Intermediate values for reduced damping performance cannot
be read out.
- A prognosis on service life is not permitted.
- Measured values that occur with the involvement of the
suspension travel end stops are incorrect.
The following values apply only to the test stands named
above. If the specified values are exceeded, the shock absorber
function has weakened enough that a replacement is recommended.
Example:
Threshold = 70
- a = greater than 70: insufficient damping effect
- a = less than 70: sufficient damping effect
The shock absorber combination installed in the vehicle is
indicated by the corresponding PR number on the vehicle data
label.
Production Control Number (PR number) explanation. Refer to
→ Chapter "Production Control Number (PR Number) Explanations".
Threshold "a" in mm
Note
- If the readout value is greater than the threshold "a"
(table value): insufficient damping effect ⇒ replace shock
absorber.
- If the readout value is less than the threshold "a" (table
value): sufficient damping effect ⇒ shock absorber does not need
to be replaced.
Guidelines for Clean Working Conditions
- Thoroughly clean connecting points and their surrounding
areas before loosening.
- Place removed parts on a clean surface and cover them so
that they do not get dirty. Use foil and paper. Only use
lint-free cloths.
- Only install clean parts: Remove the replacement parts from
their packaging just before installing them.
- Only use greases and sealants that are designated with part
numbers.
- Carefully cover or seal opened components if the repair is
not performed immediately.
READ NEXT:
Caution
There is a risk of damaging the threads in the
vehicle body.
The bolts and nuts at all suspension parts must not
be loosened or tightened with an impact wrench.
Always install th
Special tools and workshop equipment required
Engine and Gearbox Jack -VAS6931-
Tensioning Strap -T10038-
Engine/Gearbox Jack Adapter - Wheel Hub Support -T10149-
Note
All bolts on chassi
Front Gas-Filled Shock Absorbers, Venting and Draining
Special tools and workshop equipment required
Hand drill
3 mm diameter drill bit.
6 mm diameter drill bit
Oil collecting container
Protecti
SEE MORE:
Component Location Overview - Antenna Systems, Sedan, USA
1 - Antenna Amplifier -R24-
Removing and Installing. Refer to
→ Chapter "Antenna Amplifier -R24-, Removing and Installing, Sedan".
TV Antenna Amplifier 1 -R82-
Removing and Installing. Refer to
Special tools and workshop equipment required
Vehicle Diagnostic Tester
Torque Wrench 1331 5-50Nm -VAG1331-
Torque Wrench 1331 Insert - Ring Wrench - 16mm -VAG1331/12-,
not illustrated
Torque Wrench 1332 40-200Nm -VAG1332-
Engine and Gearbox Jack -VAS6931-
Engine/Gearbox Jack Adapter - Wheel