Audi Workshop Service and Repair Manuals

Note:

• ◆ The complete brake master cylinder and brake servo can be replaced separately from each other.
• ◆ Brake master cylinders cannot be dismantled any further, i.e. no provision is made for servicing.
• ◆ Use only fresh brake fluid. Refer to information on brake fluid reservoir.
• ◆ Assignment of brake pipe connections =>Repair group 45.

• Bolt, Torx socket T45, 25 Nm
• Self-locking hexagon nut, 49 Nm

• Brake master cylinder, ø23.81 mm
• ◆ Cannot be repaired. If faulty, renew complete.
• ◆ Removing and installing
  
• Brake line 15 Nm
• ◆ Brake master cylinder/floating piston circuit to hydraulic unit
• Brake line 15 Nm
• ◆ Brake master cylinder/push rod piston circuit to hydraulic unit
• Sealing ring
• ◆ Always replace

• Brake servo
• ◆ On petrol engines the required vacuum is taken from the intake manifold.
• ◆ On diesel engines an exhauster pump is installed to create the required vacuum.
• ◆ Functional test
• ‒ With the engine switched off, firmly depress the brake pedal several times (this reduces the vacuum present in the servo unit).
• ‒ Now depress brake pedal with moderate force, hold and start engine. If the servo unit is working properly, the pedal will be felt to give slightly when pressed (servo assistance becomes effective).
• ◆ If faulty renew complete.
• ◆ Non-return valve, item 9 (in vacuum hose)
• ◆ Removing and installing
  => Page 47-62

• Seal
• Vacuum hose
• ‒ Insert into brake servo unit
• Brake fluid reservoir
• Cap
• Sealing plug
• Supply hose
• ◆ From brake fluid reservoir to clutch master cylinder
• Bulkhead

→ Fig.1    Adjusting ball head

LHD vehicles:

• A = 159 mm ± 0.5 mm

RHD models

• A = 173.2 mm ± 0.5 mm

Notes:

• ◆ When measuring, the ball head should be aligned at right angles to the surface of the brake servo unit.
• ◆ Measure without gasket up to the end of ball head.