LI32.50-P-074277

Noise Complaints eABC (eSuspension)
Topic number
LI32.50-P-074277
Version
1
Function group
32.50 - Active Body Control (ABC)
Date
1/27/22
Validity
Model series 223 with SA code 490/eABC.
Except AMG model designations.
Reason for change
Complaint
1. Noises in recovery mode with the vehicle stationary
2. Noises when driving in a straight line on rough terrain
3. Noises when cornering and performing alternate steering movements
4. Non-assignable noises
Attachments
File
Description
BouncingNoise.MOV
1. and 2. Normal operating noises of the high-pressure
pump in recovery mode and when driving in a straight line
on rough terrain.
VID_20200907_165939_cut.mp4
3.Reversing noise of the high-pressure pump when steering quickly in the opposite direction
Cause
Complaint 1. Noises in recovery mode with the vehicle stationary
Complaint 2. Noises when driving in a straight line on rough terrain
Cause: These are normal operating noises of the hydraulic high-pressure pumps.
Explanation: This is the "preview noise" which is heard when recovery mode is in operation, but which can also occur
when driving over very uneven ground in the Comfort and Curve drive programs.
This is a normal operating noise which is caused by the hydraulic high-pressure pumps (MPE).
To compensate for the unevenness of the ground, large oil flows need to be generated and to do so, the MPEs turn at
very high rotational speeds.
Note:
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In the "ECO" drive program, the "Preview" function is deactivated so these noises should not occur when driving over
uneven terrain; however the vehicle body will move noticeably.
3. Noises when cornering and performing alternate steering movements - reversing noise.
Cause: Repeated rapid steering out of a curve generates a "grunting" noise.
Explanation: This noise is caused by the MPEs when the pump's direction of rotation is reversed.
Note: The reversing noise can occur in all drive programs, but is most clearly reproducible in the Curve drive program
and in Curve level 3.
Carry out an evaluation firstly in Curve levels 1 to 3 (at the highest Curve level 3, the noise will also be at its loudest!),
and then in the Comfort drive program.
4. Non-assignable noises
Cause: For procedure, see Remedy.
Remedy
Generally check whether the same noises also occur in ECO mode - in this mode the Preview/ROAD SURFACE
SCAN function is deactivated and the high-pressure pumps run at reduced speed.
Consequently, it is possible to differentiate between normal operating noises and unusual noises.
Regarding 1, 2: Explain the high-pressure system, replacing the suspension struts or pumps is not useful, as these
noises are caused by the high-pressure pump unit and should be regarded as normal operating noises.
Regarding 3: This is currently a normal operating noise and represents the series production configuration; consequently replacing the components is not useful.
Regarding 4: There will certainly be other unknown noises that we are not yet familiar with; therefore please report
these as well.
For all complaints, create a PTSS case and include:
1) Informative video recordings of the noises.
2) The driving situation in the drive program in which the noises occur should be shown.
3) For comparison, also attach a recording of this same driving situation in ECO mode.
4) Additional attachments required:
- Logs for control units N51/8, M67, M67/1, M67/2, M67/3
- Actual values for the pressures of the four hydraulic high-pressure pumps at standstill
Symptoms
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Chassis/suspension > Suspension/Dampening > Suspension system noises > whistles/hisses
Operation numbers/damage codes
Op. no.
Operation text
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Time
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Damage
code
Note
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