2017 Mercedes Benz S 63 AMG Technical Service Bulletin # LI46-20_P-048871 Date: 100218

Suspension/Steering - Front End Knocking Noises
Rattling or dull knocking noise coming from the area of the steering system when driving over rough terrain
Topic number LI46.20-P-048871
Version 1
Design group 46.20 Steering gear
Date 02-18-2010
Validity Model 221 except 4MATIC
Reason for change Content updated / Validity revised / Supersedes LI46.20-P-045884
Reason for block
Complaint:
Rattling or dull knocking noise coming from the area of the steering system when driving over rough road
Cause:

1. Prestress of steering system mounting bolts too low


2. Excessive play between thrust piece and steering rack.


3. Breakaway torque of inner and outer tie-rod ball joints is too high due to unfavorable tolerance/friction conditions.

Note:
If number 3 is the cause, the complaint is of a dull knocking noise. This occurs only at speeds between 5 and 20 km/h. Primarily after the vehicle has
spent a period out of use or after driving the vehicle in a straight line for a prolonged period of time.
Remedy:
Check and rectify the above-mentioned causes as follows:
Check prestress of steering system mounting bolts:

1. Check steering system mounting bolts using a tightening torque of 100 Nm


2. If the steering system mounting bolts cannot be turned any further, the tightening torque is OK; in this case, proceed with checking the play

between the thrust piece and steering rack

1. If the steering system mounting bolts can be turned further, i.e. the tightening torque is less than 100 Nm, proceed with point 4


2. Replace the steering system mounting bolts and tighten with the vehicle in a ready-to-drive state (standing on its wheels). Ensure that the correct

tightening torque is used for the mounting bolts: 70 Nm + 90��
Check play between thrust piece and steering rack

1. Mark position of adjustment screw (initial position) in relation to the steering gear housing


2. Tighten the adjustment screw as far as it will go (torque 110 Nm ), then turn it back approx. 1/8 of a turn

Note:
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Breakaway torque may be higher
3. Check steering for ease of movement; to do this turn the steering from lock to lock without running the engine. It should not be possible to feel
any resistance points. If resistance points are felt, slacken the adjustment screw a little more

1. Perform test drive


2. If the noise has changed or can no longer be heard, adjust the play between the steering rack and the thrust piece (see Step. 7)


3. If the noise can still be heard, turn the adjustment screw back to the marked position and proceed with checking the outer and inner tie-rod ball

joints
7. Adjust play between thrust piece and steering rack as per AR
Check outer and inner tie-rod ball joints:
1. Replace outer ball joints; before doing so, mark position of the installed outer ball joint on inner ball joint and then perform a road test (must be
performed without toe adjustment)

1. If the noise can still be heard -> Replace inner ball joints


2. If the noise can no longer be heard, adjust the front-axle toe


3. If the noise can still be heard after replacing the outer and inner tie-rod ball joints, replace the steering rack.

Symptoms
Work units
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WIS-References
Validity