F 450 4WD Super Duty V10-6.8L VIN D (2004)
Vacuum Brake Booster: Testing and Inspection
Brake Booster
1. 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.
2. Hold the brake pedal in the applied position.
3. Start the engine.
4. If the power brake system is functioning correctly, the brake pedal can be felt to move downward after the engine starts.
5. 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. Refer to: Power Brake Assist / Hydraulic Brake Booster, See: Hydraulic Brake Booster/Service and Repair
If power steering pump pressure is not available at the Hydro-Boost power brake booster, check the power steering pump pressure and flow. Refer
to: Steering / Testing and Inspection, See: Steering and Suspension/Steering/Testing and Inspection/Component Tests and General Diagnostics
On a Hydro-Max booster system, if power is available at the electric pump and no power assist is felt, replace the Hydro-Max booster assembly
and retest the system.
If power is not available at the electric pump, correct the electrical concern and retest the system.
