E 250 V10-6.8L VIN S (2005)
Vacuum Brake Booster: Testing and Inspection
Brake Booster
1. With the engine OFF, apply the brake pedal several times to deplete the power assist reserve in the brake booster.
2. Hold the brake pedal in the applied position.
3. Start the engine.
4. The brake pedal should drop slightly after the engine starts.
5. On vacuum brake booster equipped vehicles, if the brake pedal does not drop after the engine is started, check for vacuum at the brake booster.
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With the engine OFF, disconnect the vacuum hose and check valve at the brake booster.
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Vacuum should be heard escaping from the brake booster.
6. If vacuum is not available at the brake booster, check for vacuum at the source and check the vacuum hose for leaks.
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On vehicles without a vacuum pump, check for vacuum at the engine.
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On vacuum pump equipped vehicles, inspect the accessory drive and accessory drive belt.
7. If vacuum is available at the brake booster and no power assist is felt, install a new brake booster and retest the system.
8. On Hydro-Boost equipped vehicles, if the brake pedal does not drop after the engine is started, check the power steering pump pressure and flow.
9. If power steering pump pressure is available to the Hydro-Boost and no power assist is felt, install a new Hydro-Boost(R) brake booster and retest
the system.