Brake Booster Function Test
WARNING: This page does not describe the selected car, but rather 13 other vehicles, including the 2004 Ford Pickup, 2004 Ford F550 Super Duty, 2004 Ford F450 Super Duty, 2004 Ford Excursion, and 2003 Ford Pickup. However, it is still accessible from the selected car via links, so may be relevant.
- With the transmission in NEUTRAL and the engine stopped, apply the brakes several times to exhaust the vacuum in the vacuum boost system or the pressure in the Hydro-Boost system.
- Hold the brake pedal in the applied position.
- Start the engine.
- If the power brake system is functioning correctly, the brake pedal can be felt to move downward after the engine starts.
- With a vacuum type power brake booster, if engine vacuum is available to the power brake booster and no power assist is felt, replace the power brake booster and retest the system.
- If power steering pump pressure is available to the Hydro-Boost power brake booster and no power assist is felt, replace the Hydro-Boost power brake booster and retest the system.
- If power steering pump pressure is not available at the Hydro-Boost power brake booster, check the power steering pump pressure and flow. See appropriate POWER STEERING article in STEERING.
- On vehicles with Hydro-Boost, start and run the engine.
- Stop the engine.
- Apply the brakes. The accumulator in the Hydro-Boost power brake booster should retain enough pressure for at least 2 power assisted brake operations. If no power assist is felt, replace the Hydro-Boost power brake booster and retest the system.