F 350 2WD Pickup V8-7.3L DSL (1988)
Hydraulic Brake Booster: Initial Inspection and Diagnostic Overview
Operation Conditions
Normal hydro-boost units will produce certain noises that current technology cannot correct. These noises occur when brake pedal is manipulated in a
manner not associated with everyday braking habits. Normal operating noise can be a hissing, clunk, click or a chatter.
If above normal pedal efforts are applied, the hydra-boost unit will emit hissing noises. These noises will be particularly noticeable with the vehicle
motionless and will increase in intensity as pedal efforts increase and system operating temperatures increase. Loud hissing noises at or below normal
pedal effort warrants investigation and possible correction.
Clunk, chatter or clicking noises will be heard when brake pedal is quickly released from hard pedal efforts and most likely be heard during fast
stop-start conditions.
Reserve Retention Check
1.
Charge system with pressure by holding steering on the stop and engine running at idle.
2.
Turn engine off, then eight to twelve hours later depress brake pedal.
3.
If there is some degree of power reserve, hydra-boost system is operational.
4.
If there is no reserve power, replace hydra-boost unit.
