pedal pressure will be noticeably higher. AVOID
DRIVING IN THIS CONDITION.
Figure 6-8.Hydrauiic power booster system.
pump (fig. 6-8) rather than vacuum from the engine. The
booster unit contains a spool valve that has an open
center that controls the pump pressure as braking occurs.
A lever assembly has control over the valve position
and the boost piston provides the necessary force that
operates the master cylinder. See figure 6-9 for a parts
breakdown of the booster assembly.
In the event of hydraulic pressure loss, a spring-
loaded accumulator is provided on the unit. This will
provide for at least two power brake applications. The
brakes will operate without the power assist unit, but the
Hard Pedal (at an idle):
This problem may be caused by fluid contami-
nation, pedal linkage binding, or a bad hydroboost unit.
High Pedal and Steering Effort:
A loose or broken power steering belt, low pump
fluid level, low engine idle, a restriction in one or more
hydraulic lines, or a defective power steering pump will
cause these symptoms.
Slow Pedal Return:
Slow pedal return can be caused by pedal linkage
binding, a restricted booster hydraulic line, or an internal
problem with the hydroboost unit.
Pedal chatter/pulsation is caused by a loose or
slipping drive belt, low power steering fluid level, a
defective power steering pump, or a defective
Figure 6-9.Hydraulic power booster assembly.