Central Hydraulic System - Vibration/Noise
88audi02Number: Group:
88-02 48
January 15, 1988
Brakes - Steering
Applies To: A11 5000 Models 1984-1987
Subject: Central Hydraulic System - Vibration/Noise
1. Noise audible outside vehicle - rattle/rapping
Cause:
Insufficient belt tension. Hydraulic pulsation and operating noise of pump.
Production Change:
Modified hydraulic pump (red tag).
As of: May 1985 VIN: 44_F_119454
Service Solution:
Increase belt tension until noise is eliminated.
NOTE: On silver tag pumps and 5 cylinder engines only: Increase belt tension even if tension seems sufficient. Pump bearings not damaged by higher belt tension.
2. Noise audible inside vehicle - buzz/pulsation at idle
Cause:
Hydraulic pulsation of lines and accumulator.
Production Change:
Modified accumulator, damper in return line.
As of: May 1987 VIN: 44_H_117300
Service Solution:
Replace damper hose, P/N 443 612 083C, if kinked or missing. Replace accumulator, P/N 857 612 061 B, if multiple pumping of brake pedal reduces noise.
3. Noise audible inside vehicle after right-hand turns - rattle, pulsating
Cause:
Tolerance deficiency in steering rack.
Production Change:
Change in preparation.
Service Solution:
Replace steel pipe from pump to outside fitting (see illustration) with damper unit, P/N 443 422 2 51 B.
NOTE: 1. When working on hydraulic pump, pump and hose must be primed with hydraulic oil, G 022,000.
2. Whenever a component has disintegrated, all lines must be flushed with hydraulic oil to remove any contaminants that may damage new components.