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Brake Booster

SECTION 206-07: Power Brake Actuation

2011 Fiesta Workshop Manual

DESCRIPTION AND OPERATION

Procedure revision date: 05/13/2010

BRAKE BOOSTER

The brake booster consists of:

brake booster assembly

brake booster vacuum hose

brake booster vacuum check valve

The brake booster is a single-diaphragm type which utilizes engine vacuum to reduce brake pedal effort and travel. The brakebooster is divided into separate vacuum and atmospheric chambers by the diaphragms. Engine vacuum is supplied to thebrake booster through the brake booster hose and a one-way check valve. The check valve retains the engine vacuum in thebrake booster and allows for several power-assisted brake applications with the engine off.

When the brake pedal is applied, vacuum replaces the atmospheric pressure in the brake booster, reducing the effort requiredat the brake pedal to slow the vehicle. When the brake pedal is released, vacuum returns to the brake booster through thebrake booster vacuum hose and check valve.

SECTION 206-07: Power Brake Actuation

2011 Fiesta Workshop Manual

REMOVAL AND INSTALLATION

Procedure revision date: 10/19/2010

BRAKE BOOSTER

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Item Part Number Description

1 9C490 Vacuum hose

2 — Spring clamp (part of 9C490)

3 2B195 Brake booster

4 2M078 Brake booster seal

5 W706840 Brake booster nut (4 required) - 25 Nm (18 lb-ft)

6 2L523 Brake booster push rod clevis locking pin

Removal and Installation

1. Remove the brake master cylinder. For additional information, referto Brake Master Cylinder in Hydraulic Brake Actuation.

2. NOTICE: Do not service the brake pedal without first removing thestoplamp switch. Remove this switch with the brake pedal in theat-rest position. Attempting to remove this switch when theplunger is extended (during pedal apply) results in damage to theswitch.

Remove the stoplamp switch. For additional information, refer toExterior Lighting.

3. NOTICE: Do not service the brake pedal without first removing thecruise control deactivator switch. Remove this switch with thebrake pedal in the at-rest position. Attempting to remove thisswitch when the plunger is extended (during pedal apply) resultsin damage to the switch.

Remove the cruise control deactivator switch. For additionalinformation, refer to Cruise Control.

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4. NOTE: The brake booster push rod clevis locking pin is a one-timeuse only part. Any time the brake booster push rod clevis locking pinis removed, install a new brake booster push rod clevis locking pin.

NOTE: Use an 11 mm, 12-point socket or wrench to compress the 2locking tabs on the brake booster push rod clevis locking pin.

Remove and discard the brake booster push rod clevis locking pin,then position the brake booster push rod aside.

5. Remove the 4 brake booster nuts.

To install, tighten to 25 Nm (18 lb-ft).

6. Remove the brake booster.

7. NOTICE: Do not press, pull or otherwise move the brake pedalwhile installing the stoplamp switch and cruise controldeactivator switch. Install these switches with the booster pushrod attached to the brake pedal and with the brake pedal in the at-rest position. Installing these switches with the brake pedal in anyother position results in incorrect adjustment and damages theswitches.

To install, reverse the removal procedure.

8. Verify correct stoplamp switch and cruise control deactivator switchinstallation. For additional information, refer to Brake Pedal SwitchAdjustment in Anti-Lock Brake System (ABS) and Stability Control.