Brake Booster Function Test
- 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.