Mustang GT V8-4.6L SOHC VIN X (1998)
Hydraulic Brake Booster: Initial Inspection and Diagnostic Overview
Inspection
Normal hydro-boost will produce certain characteristic noises that current technology cannot correct. These noises occur, for the most part, when the
brake pedal is manipulated in a manner not associated with the everyday braking habits. The general categories of normal operating noise are hissing
noise and clunk, click and chatter noises.
The hydro-boost will emit normal hissing noises when above normal pedal efforts are applied. The hiss sounds are particularly noticeable with the
vehicle motionless and will increase in intensity as pedal efforts increase and system operating temperatures increase. Loud hissing sounds at or below
normal pedal effort (111-156 N, 25-35 lbs.) warrant investigation and possible correction.
Clunk, chatter or clicking noises will be heard when the brake pedal is quickly released from high pedal efforts. The "quick release from high pedal
effort application" noises, will most likely be heard with the vehicle motionless or during a fast stop-start condition. Refer to Pinpoint Tests N, P and
Q for Hydro-Boost Power Brake Booster Diagnosis.
Cleaning and Inspection
CAUTION: Power steering fluid and brake fluid are not compatible. Do not add power steering fluid to the brake master cylinder or damage to seals
will occur. Do not add brake fluid to the power steering reservoir or damage to the seals in the steering system will occur.
Inspect power steering pump reservoir for condition of fluid. With engine off depress brake pedal 10 times to discharge the fluid in the hydro-booster
accumulator. Add power steering fluid, if necessary, to bring level to MAX fill line. Check system for signs of fluid leaks.
Visually inspect routing of tubes and hoses; make sure they do not rub against body or engine components. Power steering tubes and hoses are
serviced separately. If the hydro-boost power brake booster is damaged or inoperative, replace it with a new hydro-boost power brake booster.
