1993 CHEVROLET DYNASTY Service Manual

flat tire park assist rear view mirror seat memory interior lights tow bar

Page 177 of 2438

CHEVROLET DYNASTY 1993 Service Manual to the rear will be lower than the front brakes. This will
prevent premature rear wheel lock-up and skid. If
hydraulic pressure is lost in one half of the diagonally
split system, the operation of th

to the rear will be lower than the front brakes. This will
prevent premature rear wheel lock-up and skid. If
hydraulic pressure is lost in one half of the diagonally
split system, the operation of the proportioning valve
in the remaining half is not effected.
ABS BRAKE PROPORTIONING VALVE OPERATION
On vehicles using the ABS braking system, screw in
proportioning valves are used in place of the conven-
tional differential pressure/proportioning valve. Each rear brake circuit has its own screw-in propor-
tioning valve which is attached to the rear brake outlet
ports of the hydraulic assembly. These valves limit
brake pressure to the rear brakes after a certain
pressure is reached. This improves front to rear brake
balance during normal braking.
Screw in proportioning valves can be identified by
the numbers stamped on the body of the valve. The
first digit represents the slope, the second digit repre-
sents the split (cut-in) point, and the arrow represents
the flow direction of the valve. Be sure that the
numbers listed on the replacement valve are the
same as on the valve that is being removed. See
(Fig. 3) for detail of the valve identification.
HYDRAULIC SYSTEM SERVICE PROCEDURES
BRAKE WARNING SYSTEM
CHECKING BRAKE WARNING SWITCH UNIT
The Red Brake Warning light will come on when
the parking brake is applied with the ignition key
turned ON. The same light will also illuminate
should one of the two service brake hydraulic sys-
tems fail.
CAUTION:Make sure air does not enter the hydrau-
lic system during this test procedure. See bleeding
without a pressure bleeder at the beginning of this
section for master cylinder fluid level checking pro-
cedures.
To test the service brake warning system lamp.
Raise the vehicle on a hoist and open a wheel cylin-
der bleeder while a helper depresses the brake pedal
and observes the warning light. If the light fails to light, inspect for a burned out
bulb, disconnected socket, or a broken or discon-
nected wire at the switch. If the bulb is not burned
out and the wire continuity is uninterrupted. Check
the service brake warning switch operation with a
test lamp between the switch terminal and a known
good ground. Be sure to fill master cylinder and
bleed brake system after correction has been made, if
necessary.
PROPORTIONING VALVES
TESTING PROPORTIONING VALVE UNIT
If premature rear wheel skid occurs on hard brake
application, it could be an indication that a malfunc-
tion has occurred with the proportioning valve unit. The proportioning valve is designed with two sep-
arate systems. One half controls the right rear
brake, and the other half controls the left rear brake.
Therefore, a road test to determine which rear brake
slides first is essential.
RIGHT REAR WHEEL SLIDES FIRST To test the proportioning valve when the right rear
wheel slides first, leave the front brakes connected to
the valve, proceed as follows: (1) Install one gauge and (TEE) of set C-4007-A
between the brake line from the master cylinder sec-
ondary port and the brake valve assembly. (2) Install the second gauge of set C-4007-A to the
right rear brake outlet port (Fig. 4). Using an
adapter tube, made from a short piece of brake tube
and (2) 3/8 x 24 tube nuts. Connect the hose to the
valve. Bleed the hose and gauge. (3) Have a helper exert pressure on the brake
pedal (holding pressure) to get a reading on the valve
inlet gauge and check the reading on the outlet
Fig. 3 ABS PROPORTIONING VALVE IDENTIFICA- TION
Ä BRAKES 5 - 27

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CHEVROLET DYNASTY 1993 Service Manual PROPORTIONING VALVE APPLICATIONS
5 - 28 BRAKES Ä

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CHEVROLET DYNASTY 1993 Service Manual gauge. If the inlet and outlet pressures do not agree
with the values on the following chart, replace the
valve.
LEFT REAR WHEEL SLIDES FIRST To test the proportioning valve when the left rear
whe

Page 180 of 2438

CHEVROLET DYNASTY 1993 Service Manual PROPORTIONING VALVE PRESSURES ABS-BRAKES
PROPORTIONING VALVE PRESSURES NON-ABS BRAKES
5 - 30 BRAKES Ä

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CHEVROLET DYNASTY 1993 Service Manual FRONT DISC BRAKES INDEX
page page
General Information ....................... 31
Service Precautions ....................... 34 Shoe and Lining Wear
.................... 33
GENERAL INFORMATION
T

FRONT DISC BRAKES INDEX
page page
General Information ....................... 31
Service Precautions ....................... 34 Shoe and Lining Wear
.................... 33
GENERAL INFORMATION
The single piston, floating caliper disc brake as-
sembly (Fig. 1 and 2) consists of:
² The driving hub
² Braking disc (rotor)
² Caliper assembly
² Shoes and linings
² Adapter for mounting the caliper assembly to the
steering knuckle WARNING: THE PISTONS THAT ARE USED
IN THE 2 DIFFERENT CALIPER ASSEMBLIES
ARE UNIQUE TO THE CALIPER THEY ARE
USED IN. THE DIMENSIONS OF THESE PIS-
TONS ARE DIFFERENT, DO NOT INTER-
CHANGE THE CALIPER PISTONS.
IMPROPER USE COULD CAUSE A COM-
PLETE FAILURE OF THE BRAKE SYSTEM. The double pin Kelsey-Hayes Family Caliper, is
mounted to the adapter using bushings, sleeves and
2 through bolts threaded into the adapter (Fig. 3 and
5). The adapter is then mounted to the steering
knuckle using 2 attaching bolts. The double pin Kelsey-Hayes Non-Family Caliper,
is mounted directly to the steering knuckle of the ve-
hicle using bushings, sleeves and 2 through bolts (Fig. 4). The adapter is not used on the vehicles
equipped with the Non-Family caliper assembly.
Two machined abutments on the caliper mounting
adapter or steering knuckle, (Fig. 3 and 4) position
the caliper fore and aft. The guide pin bolts, sleeves
and bushings control the float, side to side movement
of the caliper. The piston seal, is designed to pull the
piston back into the bore of the caliper when the
brake pedal is released. This maintains proper brake
shoe to rotor clearance (Fig. 6). Vehicles equipped with Kelsey-Hayes double pin
family calipers, have 1 anti-rattle clip attached to
the top of the adapter (Fig. 1). All of the braking force is taken up directly by the
adapter or the steering knuckle depending on the
type of caliper assembly the vehicle is equipped with. The caliper is a one piece casting with the inboard
side containing a single piston cylinder bore. The front disc brake caliper phenolic piston is 2 dif-
ferent sizes depending on the vehicle that the caliper
assembly is used on. The AC, AG & AY body use a
60 mm piston, and the AA, AP, AG & AJ body use a
54 mm piston.
Fig. 1 Front Disc Brake Assembly (Family Caliper Typical)
Ä BRAKES 5 - 31

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CHEVROLET DYNASTY 1993 Service Manual A square cut rubber piston seal is located in a ma-
chined groove in the cylinder bore. This provides a
hydraulic seal between the piston and the cylinder
wall (Fig. 6). A molded rubber dust boot is

Page 183 of 2438

CHEVROLET DYNASTY 1993 Service Manual semblies. This sensor when emitting a sound signals
that brake lining may need inspection and/or re-
placement.
SHOE AND LINING WEAR
If a visual inspection does not adequately deter-
mine the conditi

Page 184 of 2438

CHEVROLET DYNASTY 1993 Service Manual SERVICE PRECAUTIONS
WARNING: DUST AND DIRT ON BRAKE PARTS
GENERATED DURING THE NORMAL USE AND
WEAR OF MOTOR VEHICLE BRAKE SYSTEMS CAN
CONTAIN ASBESTOS FIBERS. BREATHING EXCES-
SIVE CONCENTRATIONS OF

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