Suspension - Front Axle Dull Thumping Noise On Bumps

Mercedes Benz C 250 (204.052) (CANADA) V6-2.5L (272.921) Technical Service Bulletin # LI32-25_P-0483812 Date: 110214

Suspension - Front Axle Dull Thumping Noise On Bumps

Noises from area of front axle on uneven roads

Topic number LI32.25-P-048381

Version 2

Design group 32.25 Shock absorbers/damper struts/spring struts

Date 02-14-2011

Validity MODEL 204

- without CODE (483) Vehicle dynamics package,

- without (204.#77) AMG

Reason for change Reference to separate LI on topic of front axle suspension struts

Complaint:

Dull thumping noises or metallic rattling from the area of the front axle on slightly uneven roads or on repaired road surfaces.

Note:

The noises occur in the lower vehicle speed range (20 ... approx. 70 km/h).

Cause:

Several causes are possible:

1. Rigidity (Shore hardness) of the head bearings on the suspension struts of the front axle is too high.

Note:

Noises from the head bearing occur on larger undulations and sound relatively dull.

This cause only affects a small, limited production batch! - Always observe the VIN range stated below for the head bearing/strut tower

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bearing for the validity! On vehicles outside this range the head bearing is not the cause of the noise and therefore must not be replaced.

2. Front axle shock absorber

Note:

See LI "Noises from area of front axle suspension struts"

Note:

Noises from the shock absorber are audible on small undulations and have a more metallic sound.

3. Torsion bar linkage

Note:

Noises caused by the torsion bar linkage are known only in a very few isolated cases in this model series.

In other words, it is generally not the source of the noise, so please follow the procedure described below.

Remedy:

Note:

For noise diagnosis the use of the STEELMAN ChassisEAR is helpful and it should be used if there is any uncertainty.

Drive on uneven and smooth surfaces alternately in order to identify the affected component.

If necessary, perform a test drive without the torsion bar linkage (EPC: "torsion bar rod and shock absorber") in order to eliminate it with

certainty.

Check torque specifications (see WIS) of torsion bar linkage beforehand and correct if necessary.

Re.cause 1 (dull noises on larger undulations):

Affected VIN number range: 204.0## #A 185017 up to * 195993 for head bearing

- Replace head bearing/ strut tower bearing (EPC designation: "suspension strut bearing on body").

Re.cause 2 (metallic noises on smaller undulations):

Replace front axle suspension struts.

Note:

See LI32.25-P-051123 "Noises from area of front axle suspension struts".

Re.cause 3:

Replace torsion bar linkage.