F 150 2WD Pickup V8-4.6L VIN W (2006)
Vacuum Brake Booster: Testing and Inspection
Brake Booster
1. Check the hydraulic brake system for leaks or insufficient fluid.
2. With the transmission in NEUTRAL, stop the engine and apply the parking brake control. Apply the brake pedal several times to exhaust all
vacuum in the system.
3. Apply the brake pedal and hold it in the applied position. Start the engine. If the vacuum system is operating, the brake pedal tends to move
downward under constant foot pressure. If no motion is felt, the brake booster system is not functioning. Continue with the following steps.
4. Remove the vacuum booster hose from the check valve connection. Manifold vacuum must be available at the check valve end of the vacuum
booster hose with the engine at idle speed and the transmission in NEUTRAL. Connect the vacuum booster hose to the brake booster check valve
and verify that the manifold vacuum is available to the brake booster.
5. Operate the engine a minimum of 10 seconds at fast idle. Stop the engine, and let the vehicle stand for 10 minutes. Then apply the brake pedal with
approximately 89 N (20 lb) of force. The brake pedal feel should be the same as that noted with the engine operating. If the brake pedal feels
hard or no downward movement is felt (indicating no power assist), install a new brake booster check valve and retest. If the concern is still
present, install a new brake booster. If the brake pedal feels spongy, bleed the hydraulic system to remove air.
