A4 Quattro Wagon L4-1.8L Turbo (AEB) (1999)
Brake Master Cylinder: Description and Operation
W/ 23.81 mm (0.937) Piston Diameter
Brake master cylinder with 23.81 mm (0.937 inch) piston diameter and brake servo, component summary
Note:
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Brake master cylinders and brake servos can be replaced separately.
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Brake master cylinders can no longer be disassembled, i.e. there is no provision for servicing.
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Use only fresh brake fluid. Pay attention to information on the brake fluid reservoir.
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Brake line connections to master cylinder. Refer to Anti-lock Brake System (ABS), Bosch. Bosch 5.3 system, refer to Anti-lock Brake System
(ABS).
1. T45 Torx(R)
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25 Nm (18 ft. lbs.)
2. Self-locking nut
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49 Nm (36 ft. lbs.)
3. Brake master cylinder
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Diameter: 23.81 mm (0.937 inch)
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Cannot be repaired. If malfunctioning, replace as complete unit only.
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Removing and installing. Refer to Brake master cylinder with 23.81 mm (0.937 inch) diameter piston, removing and installing.
4. Brake line
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15 Nm (11 ft. lbs.)
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Brake master cylinder/secondary piston circuit to hydraulic control unit
5. Brake line
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15 Nm (11 ft. lbs.)
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Brake master cylinder/primary piston circuit to hydraulic control unit
6. Seal
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Always replace
7. Brake servo
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On gasoline engines vacuum is supplied from the intake manifold
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On Diesel engines vacuum is supplied from the vacuum pump
Functional check:
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With engine switched off, depress brake pedal firmly several times (to deplete vacuum in brake servo).
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Depress and hold brake pedal with average foot pressure and start engine. If servo is working properly, pedal will be felt to give slightly under
foot (servo assistance becomes effective).