Whistling noise when Operating the brake pedal - AF42.46-P-1000AG

MODEL 211, 219 up to Model year 2006 (code 806) 

OPERATION NO. OF OPERATION TEXTS OR STANDARD TEXTS AND FLAT RATES

Category	Op. no.	Operation text
PP.	023970	Retrofit flex lines (HZ1 and HZ2) and return line
PP.	024004	Retrofit flexlines (HZ1 and HZ2), right-hand drive vehicle

Damage code	Cause	Remedy
43 102 36	The application of a voltage to the coils for the separation valves of the SBA hydraulic unit causes a high-frequency whistling sound. These noises are transmitted via the brake lines to the Operating unit and from there via the brake pedal to the interior.	1 Instead of steel lines, install two flexlines (HZ1 and HZ2) for decoupling the whistling noise. When routing the new lines, take extreme care to ensure that the lines do not touch other components and are not stressed.
	Soft, high-frequency (4 kHz) whistling sound when Operating the brakes. This occurs each time the brake is operated and lasts for the complete duration of the brake operation.	If this is ignored, the complaint cant be rectified.
	The high-frequency (4 kHz) whistling noise must not be confused with a pressure buildup or pressure reduction noise which only occurs briefly during the operation and/or release of the brake pedal.	On left-hand drive vehicles a modified return line is required in addition to the two flex lines. Right-hand drive vehicles do not require a modified return line.
	Pump running noise from the SBA hydraulic unit can still not be eliminated by this action.	Remedy for pump running noises, see: ↓
		Humming/droning noise during SBA system charging process	AF42.46-P-1101A
		This remedy is only for the above- mentioned high-frequencies (4 kHz) whistling noise. Other noises cant be eliminated by the flex lines.

PARTS ORDERING NOTES

Part no.	Designation	Quantity
211 428 42 00	Flex line, left-hand drive vehicle (HZ1)	As required
211 428 43 00	Flex line, left-hand drive vehicle (HZ2)	As required
211 428 20 00	Return flow pipe Is only required for a left-hand drive vehicle.	As required
211 428 44 00	Flex line RL (HZ1)	As required
211 428 45 00	Flex line RL (HZ2)	As required