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Vacuum Booster Function Test

WARNING: This page is about a different car, the 2004 Ford Escape, 2003 Ford Escape, and 2002 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.
  1. Inspect all vacuum hoses and connections. All unused vacuum connectors must be capped. Hoses and their connections must be correctly secured and in good condition with no holes, cracks, or collapsed areas.
  2. Check the brake hydraulic system for leaks or insufficient brake fluid. Repair as necessary.
  3. With the engine off, place the transaxle in Park (A/T) or Neutral (M/T) and apply the parking brake.
    4. NOTE: If the power brake booster is noisy when the brakes are applied, a new component must be installed.
  4. Press the brake pedal several times to exhaust all of the vacuum from the system.
  5. Press and hold the brake pedal.
  6. Start the engine. If the vacuum system is operating, the brake pedal will move downward under constant foot pressure. If no movement occurs, the power brake booster system is not functioning.
  7. Remove the vacuum booster hose from the power brake booster.
  8. Place the transaxle in PARK (A/T) or NEUTRAL (M/T) and apply the parking brake. Start the engine. Manifold vacuum should be available from the vacuum booster hose. If manifold vacuum is not available, inspect all of the hoses and hose connections. Repair as necessary.
  9. Reconnect the vacuum booster hose and run the engine at fast idle for 10 seconds.
  10. Stop the engine and let the vehicle stand for 10 minutes.
  11. Apply the brake pedal with approximately 20 lbs. of force. The brake pedal feel should be the same as normal power assisted brake operation for at least one application. If the brake pedal feel is normal, then the power brake booster is okay. If the brake pedal feels hard, continue with the test.
  12. Remove the vacuum booster hose from the power brake booster. Apply 17 in. Hg (57.3 kPa) of vacuum to the vacuum booster hose. If the vacuum does not leak off after 10 minutes, install a new power brake booster. If the vacuum does leak off, install a new check valve and/or new vacuum booster hoses.
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