Disc Brakes Audi TT 8N

BRAKE SYSTEM IDENTIFICATION

TT models are equipped with one of several brake systems. Brake caliper application is designated by the Production Code (Pr. No.). Pr. No. is printed on vehicle data sticker located in spare tire well or in owners customer's service schedule. (Scheme 1) For brake caliper Pr. Nos., see PRODUCTION CODES table. To identify brake system and components (Scheme 2)- (Scheme 4).

PRODUCTION CODES

Scheme 1

Scheme 2

Scheme 3

Scheme 4

DESCRIPTION & OPERATION

All models have self-adjusting front and rear disc brakes. The cable actuated parking brake mechanically activates the rear calipers.

Hydraulic system uses a tandem master cylinder with vacuum assist. Hydraulic system is diagonally split. Left front and right rear wheels form one circuit. Right front and left rear wheels form the other circuit. The brake pressure regulator has been deleted, as regulation function has been replaced by ABS control module programming.

From 2001 models on, certain gasoline engine versions in conjunction with automatic transmission are equipped with an electric vacuum pump to boost the vacuum supplied to the brake servo. Electric vacuum pump is OBD capable. For pump diagnostics, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.

BLEEDING PROCEDURES

Note. Brake fluid should be replaced every 2 years regardless of elapsed mileage.

Pre-Bleeding When One Chamber In The Brake Fluid Reservoir Is Completely Empty

System must first be pre-bled when one chamber in the brake fluid reservoir is completely empty (for example, brake system leaking). See BLEEDING WHEN MASTER CYLINDER RESERVOIR IS EMPTY . Afterward the hydraulic unit must be bled with vehicle diagnostic, testing and information system VAS 5051 in function "04 - Basic setting.

Standard Procedure

1. Ensure brake master cylinder reservoir is full. Connect hose to brake caliper bleed screw and insert other end of hose in a clear container 1/4 full of clean brake fluid. Bleed brake calipers in following sequence: Left Front Caliper Right Front Caliper Left Rear Caliper Right Rear Caliper
2. About 1/2 pt. (200 cc) of brake fluid is expelled from each wheel when bleeding entire system. Top off fluid level in reservoir to MAX mark and close reservoir cap. Before driving vehicle, depress brake pedal several times to ensure brakes are working correctly.

With Brake Filler & Bleeder Unit

Note. When using a brake system filling and bleeding appliance (such as VAS 5234) to replenish the brake fluid, make sure that filling pressure does not exceed 15 psi (1 bar). If the filling pressure exceeds 15 psi (1 bar), a hydraulically controlled change-over valve (which is required for the Electronic Differential Lock (EDL) function) prevents unrestricted flushing of the EDL-related parts of the hydraulic unit. If this is the case, it may not be possible to bleed the system properly. For this reason the brake fluid pressure must be reduced to 1 bar on the brake filler and bleeding unit.

1. Connect pressure bleeder (VAS 5234) or equivalent, to master cylinder reservoir. Connect hose to brake caliper bleed screw and insert other end of hose in a clear container 1/4 full of clean brake fluid. Bleed air from brake system in following order: Left Front Caliper Right Front Caliper Left Rear Caliper Right Rear Caliper
2. About 1/2 pt. (200 cc) of brake fluid is expelled from each wheel when bleeding entire system. Top off fluid level in reservoir to MAX mark and close reservoir cap. Before driving vehicle, depress brake pedal several times to ensure brakes are working correctly.

Note. A test drive must be carried out after bleeding brakes. When doing this an ABS-controlled brake application on all four wheels must be performed at least once.

Bleeding When Master Cylinder Reservoir Is Empty

Note. System must first be pre-bled when one chamber in the brake fluid reservoir is completely empty.

Bleed the hydraulic unit using Basic Setting. See BASIC SETTING (FUNCTION 04) .

BRAKELIGHT SWITCH

Remove driver's side knee bolster/storage tray. (Scheme 5) Working under dash, disconnect brake light switch harness connector. Remove brake light switch by turning brake switch (round housing 45 degrees to left; square housing 90 degrees to left). Pull plunger on switch out as far as possible by hand. (Scheme 6)or (Scheme 7). Being careful not to press down on brake pedal, guide switch into mounting bracket. Install switch (round housing 45 degrees to left; square housing 90 degrees to left). Brake switch adjusts automatically. Connect brake light switch harness connector.

Scheme 5

Scheme 6

Scheme 7

POWER BOOSTER PUSH ROD

Note. No adjustment procedure is available.

PARKING BRAKE

Note. Adjust parking brake only if parking brake cable, rear brake pads or rear caliper have been replaced.

Remove switch mount in rear center console. (Scheme 8) Remove lid for rear center console. With parking brake lever in released position, tighten adjustment nut enough to lift levers off rear brake caliper stops. Maximum gap is.120" (3 mm) (arrow in illustration). Apply parking brake 3 times. With parking brake in released position, ensure that rear wheels turn freely.

Scheme 8

BRAKE PAD WEAR INDICATOR

Brake pads that have reached the end of their service life are indicated on instrument cluster by the Brake Pad Wear Indicator. Indicator will go out when NEW brake pads with NEW brake pad wear sensors are installed on vehicle.

POWER BOOSTER

With engine switched off, depress brake pedal firmly several times (to exhaust the vacuum in the unit). Depress brake pedal with average foot pressure, hold and start engine. If the booster unit is working properly, the pedal will give slightly under foot (booster assistance becomes effective). Vacuum required for power booster is taken from the intake manifold. If a loud suction noise is heard on braking, check proper positioning of inner bellows. (Scheme 9)

Scheme 9

CHECKING INNER BELLOWS OF BRAKE BOOSTER

1. Remove driver's side storage compartment. (Scheme 5)
2. Check whether bellows have slipped out of annular groove. (Scheme 10) If bellows have slipped out of groove. Remove brake-pedal mounting bracket and re-insert bellows.

Scheme 10

CHECKING NON-RETURN VALVE

Non-return valve (A) should be open and allow passage of air in direction of arrow (blow into valve). (Scheme 11) Valve should remain closed in opposite direction and not allow air to pass. When installing pay attention to correct installation position.

Scheme 11

Description & Function

The electric vacuum pump is only installed in vehicles with automatic transmission. It is switched on by Engine Control Module (ECM) depending on intake manifold pressure. Vacuum pump is On Board Diagnostic (OBD) capable. Detected malfunctions are stored in Engine Control Module (ECM) memory. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. Testing function of electric vacuum pump via On Board Diagnostic (OBD) must only be performed with engine at standstill.

Testing

1. Drive vehicle onto lifting platform, turn engine off. Start engine. While the engine is being started the electric vacuum pump should run briefly. Electric vacuum pump is located on subframe in front of steering box, left side. Have an assistant touch the pump by hand to check whether it is running.
2. If electric vacuum pump does not run, check fault memory in the engine control module.
3. If problem is found, repair as necessary. If no problem with wiring, replace electric vacuum pump. See «ELECTRIC VACUUM PUMP»(/audi/tt/8n-1998-2003/remont/mechanical-hydraulic/#disc-brakes) under REMOVAL & INSTALLATION.

ELECTRIC VACUUM PUMP

1. Locate electric vacuum pump on subframe in front of steering box, left side. (Scheme 12) Unscrew hex bolt securing guard plate. Unscrew bolts on bracket for vacuum pump.
2. Disconnect vacuum hose (arrow) from vacuum pump. Disconnect electric vacuum pump harness connector. Remove pump.
3. To remove bracket (arrow), unscrew nut (2) from bolt (1). Remove bolt (4) and detach bracket. To disassemble bracket further, remove bolts (3). Installation is reverse of removal procedure.

Scheme 12

FRONT CALIPER

1. Raise and support vehicle. Remove wheels. If replacing calipers, go to next step. If only brake pads are being replaced, go to step 3.
2. Insert Brake Pedal Depressor (VAG 1869/2) or equivalent, between brake pedal and driver's seat. Depress brake pedal by at least 2.4" (60 mm). Pressing down the brake pedal closes the valves in the brake master cylinder to prevent the brake fluid reservoir from running dry. Remove brakeline from caliper, plug openings and go to next step.
3. Pry off brake pad retaining spring from brake caliper housing using a screwdriver and remove. (Scheme 2)or (Scheme 3). Remove protective caps from guide pins. Remove guide pins, and remove caliper.
4. To install, reverse removal procedure. Tighten mounting bolts to specification. See «TORQUE SPECIFICATIONS»(/audi/tt/8n-1998-2003/remont/mechanical-hydraulic/#disc-brakes__torque-specifications). Bleed hydraulic brake system. See «BLEEDING PROCEDURES»(/audi/tt/8n-1998-2003/remont/mechanical-hydraulic/#disc-brakes__bleeding-procedures) under BLEEDING BRAKE SYSTEM.

FRONT PADS

Note. If re-using brake pads, mark them so that they can be installed in their original positions to prevent uneven braking.

Removal (FN3)

1. Raise and support vehicle. Remove front wheels. Secure brake disc with a wheel bolt.
2. Remove guide pin protective caps. (Scheme 2)or (Scheme 3). Using a flatbladed tool, pry off brake pad retaining spring from brake caliper housing and remove.
3. Remove both guide pins from brake caliper. Remove brake caliper housing and support so that the weight of the brake caliper does not burden or damage the brake hose. Remove brake pads from brake pad carrier.

Installation (FN3)

Note. Before pressing the piston back, draw off brake fluid from the reservoir with a bleeder bottle. Otherwise if reservoir has been topped off, fluid will overflow and cause damage.

1. To install brake pads, press piston back into caliper housing using resetting tool before inserting new brake pads.
2. Insert brake pad with retaining spring in brake caliper housing. Inner pad (with spring) is marked with an arrow. The arrow must point in the direction of forward rotation of the brake disc when installed. (Scheme 13) Noise may result from incorrect installation.
3. Remove protective foil on backing plate of outer brake pad. Install outer brake pad on brake carrier. Install brake caliper housing in brake carrier using both guide pins, and tighten to specification. See «TORQUE SPECIFICATIONS»(/audi/tt/8n-1998-2003/remont/mechanical-hydraulic/#disc-brakes__torque-specifications).
4. Install both protective caps. Install retaining spring in brake caliper housing. Retaining spring must be pressed under brake carrier after it is inserted in both holes. If the spring is improperly installed, the brake caliper cannot adjust to compensate for wear on the outer brake pad. This will cause the brake pedal travel to increase.
5. Install wheels and tighten to specification. See «TORQUE SPECIFICATIONS»(/audi/tt/8n-1998-2003/remont/mechanical-hydraulic/#disc-brakes__torque-specifications). After installing brake pads and before moving vehicle, depress brake pedal several times firmly to properly seat brake pads in their normal operating position. Check brake fluid level, and top off as necessary.

Scheme 13

Removal (2FN)

1. Raise and support vehicle. Remove front wheels. Push retaining spring in upwards direction and remove from brake caliper sideways. (Scheme 3) Remove guide pin protective caps. Disconnect brake pad wear indicator harness connector. Lift securing strap slightly at bottom of harness connector and then rotate 90°. Remove harness connector from bracket.
2. Remove both guide pins from brake caliper. Remove brake caliper housing and secure with wire so that the weight of the brake caliper does not stress or damage brake hose. Remove brake pads from brake caliper housing.

Installation (2FN)

Note. Before pressing the piston back, draw off brake fluid from the reservoir with a bleeder bottle. Otherwise if reservoir has been topped off, fluid will overflow and cause damage.

1. Before inserting new brake pads, press piston back into the cylinder with piston resetting tool. Install brake caliper housing with brake pads on wheel bearing housing, lower part of brake caliper housing first. Brake caliper housing lug must be behind the wheel bearing housing guide.
2. Secure brake caliper housing to brake carrier with both guide pins and tighten to specification. See «TORQUE SPECIFICATIONS»(/audi/tt/8n-1998-2003/remont/mechanical-hydraulic/#disc-brakes__torque-specifications) .
3. Install wheels and tighten to specification. See «TORQUE SPECIFICATIONS»(/audi/tt/8n-1998-2003/remont/mechanical-hydraulic/#disc-brakes__torque-specifications) . After installing brake pads and before moving vehicle, depress brake pedal several times firmly to properly seat brake pads in their normal operating position. Check brake fluid level, and top off as necessary.

FRONT & REAR ROTOR

Note. On models equipped with 2FN brake system left and right discs are different; arrow shows direction of rotation. (Scheme 3)

Removal & Installation

1. Raise and support vehicle. Remove wheels. Remove brake calipers. See «FRONT CALIPER»(/audi/tt/8n-1998-2003/remont/mechanical-hydraulic/#disc-brakes__front-caliper) or «REAR CALIPER»(/audi/tt/8n-1998-2003/remont/mechanical-hydraulic/#disc-brakes__rear-caliper). Remove brake pad carrier-to-wheel bearing housing bolts. (Scheme 2)- (Scheme 4). Remove rotor-to-hub fastener. Slide rotor off hub.
2. To install, reverse removal procedure. Tighten fasteners to specification. See «TORQUE SPECIFICATIONS»(/audi/tt/8n-1998-2003/remont/mechanical-hydraulic/#disc-brakes__torque-specifications). If hydraulic system was opened, bleed hydraulic brake system. See «BLEEDING PROCEDURES»(/audi/tt/8n-1998-2003/remont/mechanical-hydraulic/#disc-brakes__bleeding-procedures) under BLEEDING BRAKE SYSTEM.

Removal

1. Remove engine cover panel to access components. Remove screws and forward left-hand cover panel. Disconnect secondary air intake hose from air cleaner (if equipped). Disconnect air hose from mass air flow sensor. Disconnect mass air flow sensor harness connector. Unscrew bolts and remove air cleaner housing. Lay out sufficient lint-free cloths in area below brake master cylinder to catch escaping brake fluid.
2. Draw off as much brake fluid as possible from brake fluid reservoir using brake filler and bleeder unit VAS 5234 or extraction unit VAG 1869/4. Clamp off clutch master cylinder supply hose with hose clamp 3094. Disconnect clutch master cylinder supply hose from master cylinder reservoir.
3. Disconnect brake fluid warning indicator sender harness connector. (Scheme 9) Disconnect brake pressure sensor harness connectors. Disconnect brake lines on brake master cylinder and seal brake lines with plugs from repair kit.
4. Remove brake master cylinder-to-brake booster nuts. Remove heat shield with retainer plate, if part of original equipment. Remove brake master cylinder from brake booster.

Installation

Installation is reverse of removal sequence; note the following points

1. Always replace sealing ring between brake master cylinder and brake booster.
2. When installing brake master cylinder, ensure that push rod in brake booster is correctly positioned. Apply slight pressure to the brake pedal; this makes it easier to guide brake master cylinder onto pushrod. Tighten fasteners to specification. See «TORQUE SPECIFICATIONS»(/audi/tt/8n-1998-2003/remont/mechanical-hydraulic/#disc-brakes__torque-specifications) .
3. Bleed brake system. See «BLEEDING PROCEDURES»(/audi/tt/8n-1998-2003/remont/mechanical-hydraulic/#disc-brakes__bleeding-procedures) under BLEEDING BRAKE SYSTEM.
4. Bleed hydraulic system for clutch.
5. Initiate basic settings for brake pressure senders. See «FUNCTION 04 - BASIC SETTING»(ref-152821-S23415383932003022700000) in ANTI-LOCK - TEVES MK 20 (WITH TCS/EDL/ESP) article.
6. On vehicles equipped with ABS/ESP Mark 60 system, perform ESP road test. Information on road testing and including Measured Value Blocks can only be found using the VAS 5051 scan tool. To access information use Guided Fault Finding. On scan tool, follow prompts through to Running Gear (Repair Group 01), Brake system MK 60, 01 On Board Diagnostic (OBD) capable systems Mark 60, ABS system ABS/EDL/ASR/ESP.

PARKING BRAKE LEVER & CABLES

Use following illustrations to aid in removal and installation of parking brake lever and cables. (Scheme 14)- (Scheme 22).

Scheme 14

Scheme 15

Scheme 16

Scheme 17

Scheme 18

Scheme 19

Scheme 20

Scheme 21

Scheme 22

CENTER CONSOLE

Use following illustrations to aid in removal and installation of center console. (Scheme 23)- (Scheme 25).

Scheme 23

Scheme 24

Scheme 25

1. Release brake booster vacuum by operating the brake pedal several times. Remove brake master cylinder. See «MASTER CYLINDER»(/audi/tt/8n-1998-2003/remont/mechanical-hydraulic/#disc-brakes__master-cylinder).
2. Disconnect vacuum hose from brake booster unit.
3. Remove driver's side knee bolster/storage tray. (Scheme 5) Working under dash, remove bolts (1). (Scheme 26) Remove cover (A) only.
4. Using Release Tool (T10006) disconnect brake pedal from power booster. (Scheme 27)
5. Remove booster-to-firewall mounting nuts. Remove power booster.

Scheme 26

Scheme 27

Installation is reverse of removal sequence; note the following points

1. Mount brake pedal on brake booster.
2. When inserting brake master cylinder, ensure that push rod in brake booster is correctly positioned. Apply slight pressure to the brake pedal; this makes it easier to guide brake master cylinder onto pushrod. Tighten fasteners to specification. See «TORQUE SPECIFICATIONS»(/audi/tt/8n-1998-2003/remont/mechanical-hydraulic/#disc-brakes__torque-specifications) .
3. Bleed brake system. See «BLEEDING PROCEDURES»(/audi/tt/8n-1998-2003/remont/mechanical-hydraulic/#disc-brakes__bleeding-procedures) under BLEEDING BRAKE SYSTEM.
4. Bleed hydraulic system for clutch.
5. Initiate basic settings for brake pressure senders. See «FUNCTION 04 - BASIC SETTING»(ref-152821-S23415383932003022700000) in ANTI-LOCK - TEVES MK 20 (WITH TCS/EDL/ESP) article.

REAR CALIPER

1. Raise and support vehicle. Remove wheels. Disconnect parking brake cables from lever on caliper. If replacing calipers, go to next step. If only brake pads are being replaced, go to step 3.
2. Insert Brake Pedal Depressor (VAG 1869/2) or equivalent, between brake pedal and driver's seat. Depress brake pedal by at least 2.4" (60 mm). Pressing down the brake pedal closes the valves in the brake master cylinder to prevent the brake fluid reservoir from running dry. Remove brakeline from caliper, and plug openings. (Scheme 4)
3. Remove protective caps from guide pins. Remove guide pins, and remove caliper from pad carrier.
4. To install, reverse removal procedure. Tighten mounting bolts to specification. If new brake calipers were installed, before pressing on brake pedal adjust parking brake. See «PARKING BRAKE»(/audi/tt/8n-1998-2003/remont/mechanical-hydraulic/#disc-brakes__parking-brake) under ADJUSTMENTS. Bleed hydraulic brake system. See «BLEEDING PROCEDURES»(/audi/tt/8n-1998-2003/remont/mechanical-hydraulic/#disc-brakes__bleeding-procedures) under BLEEDING BRAKE SYSTEM.

REAR PADS

Note. If re-using brake pads, mark them so that they can be installed in their original positions to prevent uneven braking.

1. Raise and support vehicle. Remove rear wheels.
2. Disconnect parking brake cable from caliper. Remove and discard caliper mounting bolts. (Scheme 4) Remove caliper, and wire aside. DO NOT allow caliper to hang by brake hose. Remove pads and retaining springs from caliper support.

1. Use Special Tool (VW 3272) along with Collar (3272/1) or equivalent, to seat caliper piston fully into cylinder bore. (Scheme 28) Seat piston by turning special tool until piston is bottomed out in bore. Before pressing the piston back, draw off brake fluid from the reservoir with a bleeder bottle. Otherwise if reservoir has been topped off, fluid will overflow and cause damage to finish.
2. Install brake pads, note positioning of pad to caliper (pin on pad must fit into groove on caliper piston). Pull protective foil off outer brake pad backing plate. Position caliper. Secure brake caliper housing with NEW self-locking bolts, ad tighten to specification. See «TORQUE SPECIFICATIONS»(/audi/tt/8n-1998-2003/remont/mechanical-hydraulic/#disc-brakes__torque-specifications).
3. With engine off, depress brake pedal several times to allow pads to move into operating position. Adjust parking brake as necessary. See «PARKING BRAKE»(/audi/tt/8n-1998-2003/remont/mechanical-hydraulic/#disc-brakes__parking-brake) under ADJUSTMENTS.
4. Install wheels and tighten to specification. See «TORQUE SPECIFICATIONS»(/audi/tt/8n-1998-2003/remont/mechanical-hydraulic/#disc-brakes__torque-specifications). After installing brake pads and before moving vehicle, depress brake pedal several times firmly to properly seat brake pads in their normal operating position. Check brake fluid level, and top off as necessary.

Scheme 28

FRONT CALIPER (FN3)

Remove caliper from vehicle. See FRONT CALIPER under REMOVAL & INSTALLATION. Remove pads, and clean exterior surfaces. Use air pressure to force piston from cylinder. Use a block of wood between piston and housing to prevent damage to piston. Remove dust seal. Remove piston seal without damaging bore or groove. (Scheme 29)

Scheme 29

Cleaning & Inspection

Use alcohol or brake cleaning fluid to clean hydraulic chambers. Check cylinder bore and piston for corrosion and damage. Replace defective parts as necessary.

Reassembly

1. Use all parts supplied in repair kit. Coat piston, cylinder bore and NEW seal with brake assembly or clean brake fluid. Fit piston seal into cylinder. Slide dust seal onto piston. Slowly insert piston into bore.
2. Seat inner lip of dust seal in groove on cylinder housing. Open bleed screw and push piston into bore as far as possible. Fit outer lip of dust seal into piston groove.

FRONT CALIPER (2FN)

Remove caliper from vehicle. See FRONT CALIPER under REMOVAL & INSTALLATION. Remove pads, and clean exterior surfaces. Use air pressure to force piston from cylinder. Use a block of wood between piston and housing to prevent damage to piston. Remove dust seal. Remove piston seal without damaging bore or groove. (Scheme 30)

Scheme 30

Use alcohol or brake cleaning fluid to clean hydraulic chambers. Check cylinder bore and piston for corrosion and damage. Replace defective parts as necessary.

1. Use all parts supplied in repair kit. Coat piston, cylinder bore and NEW seal with brake assembly or clean brake fluid. Fit piston seal into cylinder. Slide dust seal onto piston. Slowly insert piston into bore.
2. Seat inner lip of dust seal in groove on cylinder housing. Open bleed screw and push piston into bore as far as possible. Fit outer lip of dust seal into piston groove.

Disassembly

Remove pads, and clean outside surfaces. Use Special Tool (VW 3272) or equivalent, unscrew piston from cylinder. (Scheme 28) Carefully remove piston seal without damaging bore or groove. (Scheme 31)

Scheme 31

Use alcohol or brake parts cleaning fluid for cleaning purposes. Check cylinder bore and piston for wear and corrosion.

Use all parts supplied in repair kit. Coat piston, cylinder bore and NEW seal with a thin coat of assembly paste or brake fluid. Fit piston seal into cylinder. Slide dust seal into groove on piston. Press down on piston while screwing it into cylinder bore using Special Tool (VW 3272). Ensure outer lip of dust seal slips into piston groove.

MASTER CYLINDER

Manufacturer recommends replacement of master cylinder if defective.

VACUUM POWER BOOSTERS

Manufacturer recommends replacement of vacuum power booster if defective.

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS (FN3)

TORQUE SPECIFICATIONS (2FN)

TORQUE SPECIFICATIONS (C38 & C41)

DISC BRAKE SPECIFICATIONS

DISC BRAKE SPECIFICATIONS

See also:
• BASIC SETTING (FUNCTION 04)
• PRODUCTION CODES
• BLEEDING WHEN MASTER CYLINDER RESERVOIR IS EMPTY
• TORQUE SPECIFICATIONS
• BLEEDING PROCEDURES
• FRONT CALIPER
• REAR CALIPER
• MASTER CYLINDER
• PARKING BRAKE
• BRAKE SYSTEM IDENTIFICATION