Brake System

2. Apply the parking brake, start the engine and place the transmission in NEUTRAL. Allow the engine to reach normal operating temperature.

3. Verify that vacuum is available at the vacuum sensor/check valve with engine running at normal idle speed. The vacuum gauge should read between 51-74 kPa (15-22 in-Hg). If specified vacuum is available, stop the engine, connect the vacuum sensor/check valve and continue with Step 5. If specified vacuum is not available, continue with Step 4.

4. Disconnect the vacuum sensor/check valve from the vacuum hose and verify that the specified vacuum is available at the hose with the engine at idle speed and the transmission in NEUTRAL. If specified vacuum is available, stop the engine, install a new check valve and continue with Step 5. For vehicles equipped with a brake vacuum pump, if specified vacuum is not available, inspect the vacuum hose and install new as necessary. If the vacuum hose is ok, install a new vacuum pump. For vehicles not equipped with a brake vacuum pump, if specified vacuum is not available, stop the engine, connect the vacuum hose to the check valve and diagnose the no/low vacuum condition. REFER to: Engine (303-00 Engine System - General Information, Diagnosis and Testing).

5. Apply the brake pedal several times to exhaust all vacuum from the system.

6. Apply the brake pedal and hold it in the applied position. Start the engine and verify that the brake pedal moves downward after the engine starts. If the brake pedal moves, the brake booster is operating correctly. If the brake pedal does not move, install a new brake booster. REFER to: Brake Booster - 2.3L EcoBoost (201kW/273PS) (206-07 Power Brake Actuation, Removal and Installation). REFER to: Brake Booster - 3.7L Duratec (227kW/301PS) (206-07 Power Brake Actuation, Removal and Installation). REFER to: Brake Booster - 5.0L 32V Ti-VCT/5.2L 32V Ti-VCT (206-07 Power Brake Actuation, Removal and Installation).

7. Operate the engine a minimum of 20 seconds at idle. Stop the engine and let the vehicle stand for 10 minutes, then apply the brake pedal. The brake pedal feel should be the same as that noted with the engine operating. If the brake pedal feels hard (no power assist), install a new brake booster vacuum sensor/check valve and retest. If condition still exists, install a new brake booster. REFER to: Brake Booster - 2.3L EcoBoost (201kW/273PS) (206-07 Power Brake Actuation, Removal and Installation). REFER to: Brake Booster - 3.7L Duratec (227kW/301PS) (206-07 Power Brake Actuation, Removal and Installation). REFER to: Brake Booster - 5.0L 32V Ti-VCT/5.2L 32V Ti-VCT (206-07 Power Brake Actuation, Removal and Installation).

If the brake pedal feels the same as noted with the engine operating, the vacuum sensor/check valve is functioning properly.

Component Test- Brake Master Cylinder - Bypass Condition

1. Inspect the master cylinder.

2. Disconnect the brake tubes from the master cylinder.

3. NOTE: Make sure the outlet port plugs do not show signs of leakage.

Plug the outlet ports of the master cylinder.

4. Lightly apply the brakes and hold for 10 seconds. Release the brakes and then reapply with heavy force. If brake pedal height cannot be maintained, the brake master cylinder has an internal leak and a new brake master cylinder must be installed.

If brake pedal height is maintained, reinstall brake tubes and tighten to specification. REFER to: Brake Master Cylinder (206-06 Hydraulic Brake Actuation, Removal and Installation). After installation, bleed the brake system.REFER to: Brake System Pressure Bleeding (206-00 Brake