F 350 4WD Pickup V8-351 5.8L VIN H EFI (1997)
Vacuum Brake Booster: Initial Inspection and Diagnostic Overview
Operational Check
WARNING: USE OF ANY OTHER THAN THE APPROVED DOT 3 BRAKE FLUID WILL CAUSE PERMANENT DAMAGE TO BRAKE
COMPONENTS AND WILL RENDER THE BRAKES INOPERATIVE.
CAUTION: Always check the fluid level in the brake master cylinder reservoir before performing the test procedures. If the fluid level is not at
the MAX line on the brake master cylinder reservoir, add Ford High Performance DOT 3 Brake Fluid C6AZ-19542-AA or
equivalent DOT 3 fluid meeting Ford specification ESA-M6C25-A.
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.
1. Check hydraulic brake system for leaks or insufficient fluid. With transmission in NEUTRAL, stop engine and apply parking brake control.
2. Apply brake pedal 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.
Inspection
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Make sure the vacuum supply hose connection is secure.
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A trace of brake fluid below the brake master cylinder mounting is normal and is caused by the wiping action of the brake master cylinder piston
seals.
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Remove any debris from the power brake booster.
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Clean the power brake booster with an approved cleaner such as Multi-Purpose Cleaner Concentrate B8A-19523-AA or equivalent meeting Ford
specification ESR-M14P4-A. Inspect the power brake booster for damage, misalignment or loose mounting.
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Repair or replace the power brake booster as necessary and tighten any loose mounting nuts to specification.
