F 250 4WD Pickup V8-7.3L DSL Turbo VIN K (1994)
Vacuum Brake Booster: Testing and Inspection
VISUAL CHECKS
Inspect all hoses and connections. All unused vacuum connectors should be capped. Hoses and their connections should be properly secured and
in good condition with no holes or collapsed areas.
OPERATIONAL CHECKS
1. Check hydraulic brake system for leaks or insufficient fluid.
2. With transmission (7003) in NEUTRAL, stop engine (6007) and apply parking brake control (2780). Apply brake pedal (2455) several times to
exhaust all vacuum in the system.
3. Apply brake pedal and hold it in the applied position. Start engine. If vacuum system is operating, brake pedal will tend to move downward under
constant foot pressure. If no motion is felt, the power brake booster system is not functioning. Perform a Booster functional test.
FUNCTIONAL CHECKS
1. Remove vacuum booster hose from power brake booster and check valve connection. Manifold vacuum should be available at the check valve end
of the vacuum booster hose with engine at idle speed and transmission in NEUTRAL. If manifold vacuum is available to the power brake booster,
connect vacuum booster hose to power brake booster.
2. With transmission (7003) in NEUTRAL, stop engine (6007) and apply parking brake control (2780). Apply brake pedal (2455) several times to
exhaust all vacuum in the system.
3. Apply brake pedal and hold it in the applied position. Start engine. If vacuum system is operating, brake pedal will tend to move downward under
constant foot pressure. If no motion is felt, replace the vacuum booster.
4. Operate engine a minimum of 10 seconds at fast idle. Stop engine, and let vehicle stand for 10 minutes. Then, apply brake pedal with
approximately 89 N (20 lbs) of force. Brake pedal feel should be the same as that noted with engine operating. If brake pedal feels hard (no power
assist), replace check valve and retest. If brake pedal feels spongy, bleed hydraulic system to remove air. Refer to Brake Bleeding.
