Buick LeSabre 1965 Service Manual page 563

BRAKES
POWER BRAKES 9 - 4 1
POWER
PISTON
POWER
PISTON
RETURN
SPRING
FLOATING
CONTROL
VALVE
OPERATING
ROD
ATMOSPHERIC
PRESSURE
\ AIR VALVE
RETURN SPRING
CHECK
VALVE
ATMOSPHERIC
PRESSURE
to reopen the vacuum port and
decrease the brake application.
Whenever the pressure applied to
the brake pedal is held constant
for a moment, the valve returns
to its 'lap' or holding position.
However, upon reaching the fully
applied position, the air valve
plunger holds the floating control
valve away from the atmospheric
port seat to admit maximum at-
mospheric pressure to the cham-
ber at the right of the power
piston. With vacuum in the cham-
ber at the left of the power piston,
full power application is attained
which is referred to as the "run
out" point of the power unit. Any
increase in hydraulic pressure
Figure 9-37—Power Brake - Applied Position
beyond this point must be supplied
by physical effort of the driver.
9 - 2 4 REMOVAL,
INSTALLATION,
ADJUSTING,
TESTING OF
POWER BRAKE
UNIT
j . Removal of Power
Brake Unit
1. Disconnect brake p i p e from
hydraulic m a s t e r cylinder and
tape end of pipe to prevent en-
trance of dirt.
2. Remove retainer and special
washer from brake pedal pin and
disengage push rod eye.
3. Remove four right hand nuts
holding power brake unit to dash
panel.
4. Disconnect vacuum hose from
cylinder.
5. Remove power brake unit from
car, being careful not to d r i p
brake fluid on car paint.
6. R e m o v e filler cap and dia-
phragm and turn unit so that any
brake fluid will drain out. Pump
push rod by hand for full interior