Rear brake DODGE RAM 1500 1998 2.G Repair Manual

INSTALLATION
INSTALLATION - FRONT
(1) Bottom pistons in caliper bore with C-clamp.
Place an old brake shoe between a C-clamp and cal-
iper piston.
(2) Clean caliper mounting adapter and anti-rattle
springs.
(3) Lubricate anti-rattle springs with Mopar brake
grease.
(4) Installnewanti-rattle springs.
NOTE: Anti-rattle springs are not interchangeable.
(5) Install inboard brake shoe in adapter.
(6) Install outboard brake shoe in adapter.(7) Tilt the top of the caliper over rotor and under
adapter. Then push the bottom of the caliper down
onto the adapter.
(8) Install caliper, (Refer to 5 - BRAKES/HY-
DRAULIC/MECHANICAL/DISC BRAKE CALIPERS
- INSTALLATION).
(9) Install wheel and tire assemblies and lower
vehicle, (Refer to 22 - TIRES/WHEELS/WHEELS -
STANDARD PROCEDURE).
(10) Apply brakes several times to seat caliper pis-
tons and brake shoes and obtain firm pedal.
(11) Top off master cylinder fluid level.
INSTALLATION - REAR
(1) Clean caliper mounting adapter and anti-rattle
springs.
(2) Lubricate anti-rattle springs with Mopar brake
grease.
(3) Installnewanti-rattle springs.
NOTE: Anti-rattle springs are not interchangeable.
(4) Install inboard brake shoe in adapter.
(5) Install outboard brake shoe in adapter.
(6) Tilt the bottom of the caliper over rotor and
under adapter. Then push the top of the caliper down
onto the adapter.
(7) Install caliper, (Refer to 5 - BRAKES/HY-
DRAULIC/MECHANICAL/DISC BRAKE CALIPERS
- INSTALLATION) (Refer to 5 - BRAKES/HYDRAU-
LIC/MECHANICAL/DISC BRAKE CALIPERS -
INSTALLATION).
(8) Install wheel and tire assemblies and lower
vehicle, (Refer to 22 - TIRES/WHEELS/WHEELS -
STANDARD PROCEDURE).
(9) Apply brakes several times to seat caliper pis-
tons and brake shoes and obtain firm pedal.
(10) Top off master cylinder fluid level.
DISC BRAKE CALIPERS
DESCRIPTION
The calipers are a single piston type in the rear
and dual piston type in the front. The calipers are
free to slide laterally, this allows continuous compen-
sation for lining wear.
OPERATION
When the brakes are applied fluid pressure is
exerted against the caliper piston. The fluid pressure
is exerted equally and in all directions. This means
pressure exerted against the caliper piston and
within the caliper bore will be equal (Fig. 24).
Fluid pressure applied to the piston is transmitted
directly to the inboard brake pad. This forces the pad
lining against the inner surface of the disc brake
Fig. 22 Top Anti-Rattle Spring
1 - CALIPER ADAPTER
2 - ANTI-RATTLE SPRING
Fig. 23 Bottom Anti-Rattle Spring
1 - ANTI-RATTLE SPRING
2 - CALIPER ADAPTER
5 - 16 BRAKES - BASEDR
BRAKE PADS/SHOES (Continued)

rotor. At the same time, fluid pressure within the pis-
ton bore forces the caliper to slide inward on the
mounting bolts. This action brings the outboard
brake pad lining into contact with the outer surface
of the disc brake rotor.
In summary, fluid pressure acting simultaneously
on both piston and caliper, produces a strong clamp-
ing action. When sufficient force is applied, friction
will attempt to stop the rotors from turning and
bring the vehicle to a stop.
Application and release of the brake pedal gener-
ates only a very slight movement of the caliper and
piston. Upon release of the pedal, the caliper and pis-
ton return to a rest position. The brake pads do not
retract an appreciable distance from the rotor. In
fact, clearance is usually at, or close to zero. The rea-
sons for this are to keep road debris from getting
between the rotor and lining and in wiping the rotor
surface clear each revolution.
The caliper piston seal controls the amount of pis-
ton extension needed to compensate for normal lining
wear.
During brake application, the seal is deflected out-
ward by fluid pressure and piston movement (Fig.
25). When the brakes (and fluid pressure) are
released, the seal relaxes and retracts the piston.
The amount of piston retraction is determined by
the amount of seal deflection. Generally the amountis just enough to maintain contact between the pis-
ton and inboard brake pad.
REMOVAL
REMOVAL - FRONT
CAUTION: Never allow the disc brake caliper to
hang from the brake hose. Damage to the brake
hose will result. Provide a suitable support to hang
the caliper securely.
(1) Install prop rod on the brake pedal to keep
pressure on the brake system.
(2) Raise and support the vehicle.
(3) Remove the tire and wheel assembly.
(4) Compress the disc brake caliper.
(5) Remove the banjo bolt and discard the copper
washer.
(6) Remove the caliper slide bolts.
(7) Remove the disc brake caliper (Fig. 26) or (Fig.
27).
REMOVAL - REAR
CAUTION: Never allow the disc brake caliper to
hang from the brake hose. Damage to the brake
hose will result. Provide a suitable support to hang
the caliper securely.
(1) Install prop rod on the brake pedal to keep
pressure on the brake system.
(2) Raise and support vehicle.
(3) Remove the wheel and tire assembly.
(4) Drain small amount of fluid from master cylin-
der brake reservoir with suction gun.
(5) Remove the brake hose banjo bolt and discard
the copper washers if replacing caliper (Fig. 28).
Fig. 24 Brake Caliper Operation
1 - CALIPER
2 - PISTON
3 - PISTON BORE
4 - SEAL
5 - INBOARD SHOE
6 - OUTBOARD SHOE
Fig. 25 Lining Wear Compensation By Piston Seal
1 - PISTON
2 - CYLINDER BORE
3 - PISTON SEAL BRAKE PRESSURE OFF
4 - CALIPER HOUSING
5 - DUST BOOT
6 - PISTON SEAL BRAKE PRESSURE ON
DRBRAKES - BASE 5 - 17
DISC BRAKE CALIPERS (Continued)

(6) Remove the caliper slide bolts (Fig. 28).
(7) Remove the caliper from vehicle.
DISASSEMBLY
(1) Drain the brake fluid from caliper.
(2) C-clamp a block of wood over one piston (Fig.
29).
(3) Take another piece of wood and pad it with
one-inch thickness of shop towels. Place this piece in
the outboard shoe side of the caliper in front of the
other piston. This will cushion and protect caliper
piston during removal (Fig. 30).(4) To remove the caliper piston directshort
bursts of low pressure airwith a blow gun
through the caliper brake hose port. Use only enough
air pressure to ease the piston out.
CAUTION: Do not blow the piston out of the bore
with sustained air pressure. This could result in a
cracked piston.
Fig. 26 DISC BRAKE CALIPER - FRONT
1 - STEERING KNUCKLE
2 - DISC BRAKE CALIPER
3 - CALIPER MOUNTING ADAPTER
4 - DISC BRAKE ROTOR
Fig. 27 8 LUG ROTOR & CALIPER ASSEMBLY
1 - ROTOR
2 - CALIPER ADAPTER
3 - ANTI-RATTLE CLIPS
4 - BRAKE HOSE WITH BANJO BOLT
5 - DISC BRAKE CALIPER
6 - OUTBOARD BRAKE PAD
Fig. 28 DISC BRAKE CALIPER - REAR
1 - CALIPER ADAPTER
2 - CALIPER ADAPTER MOUNTING BOLTS
3 - CALIPER SLIDE BOLTS
4 - BRAKE HOSE
5 - CABLE
6 - CALIPER
7 - ROTOR
8 - ANTI-RATTLE CLIPS
Fig. 29 C-Clamp One Piston
1 - BLOCK OF WOOD
2 - C-CLAMP
3 - CALIPER
5 - 18 BRAKES - BASEDR
DISC BRAKE CALIPERS (Continued)

CAUTION: If the caliper piston is replaced, install
the same type of piston in the caliper. Never inter-
change phenolic resin and steel caliper pistons.
The pistons, seals, seal grooves, caliper bore and
piston tolerances are different.
The bore can belightlypolished with a brake
hone to remove very minor surface imperfections
(Fig. 34). The caliper should be replaced if the bore is
severely corroded, rusted, scored, or if polishing
would increase bore diameter more than 0.025 mm
(0.001 inch).
ASSEMBLY
CAUTION: Dirt, oil, and solvents can damage cali-
per seals. Insure assembly area is clean and dry.
(1) Lubricate caliper pistons, piston seals and pis-
ton bores with clean, fresh brake fluid.
(2) Install new piston seals into caliper bores (Fig.
35).
NOTE: Verify seal is fully seated and not twisted.
(3) Lightly lubricate lip of new boot with silicone
grease. Install boot on piston and work boot lip into
the groove at the top of piston.
(4) Stretch boot rearward to straighten boot folds,
then move boot forward until folds snap into place.
(5) Install piston into caliper bore and press piston
down to the bottom of the caliper bore by hand or
with hammer handle (Fig. 36).
(6) Seat dust boot in caliper (Fig. 37) with Handle
C-4171 and Installer:
²HD 56 mm caliper: Installer C-4340
²LD 54 mm caliper: Installer C-3716-A(7) Install the second piston and dust boot.
(8) Lubricate caliper mounting bolt bushings, boot
seals and bores with Mopar brake grease or Dow
Corningt807 grease only.
CAUTION: Use of alternative grease may cause
damage to the boots seals.
(9) Install the boot seals into the caliper seal bores
and center the seals in the bores.
(10) Install mounting bolt bushings into the boot
seals and insure seal lip is engaged into the bushing
grooves at either end of the bushing.
(11) Install caliper bleed screw.
Fig. 34 Polishing Piston Bore
1 - HONE
2 - CALIPER
3 - PISTON BORE
Fig. 35 Piston Seal
1 - CALIPER
2 - PISTON BORE
3 - PISTON SEAL
Fig. 36 Caliper Piston Installation
1 - CALIPER
2 - DUST BOOT
3 - PISTON
5 - 20 BRAKES - BASEDR
DISC BRAKE CALIPERS (Continued)

INSTALLATION
INSTALLATION - FRONT
NOTE: Install a new copper washers on the banjo
bolt when installing
(1) Install the disc brake caliper (Fig. 26) or (Fig.
27).
CAUTION: Verify brake hose is not twisted or
kinked before tightening fitting bolt.
(2) Install the banjo bolt with new copper washers
to the caliper. Tighten to 27 N´m (20 ft. lbs.)
(3) Install the caliper slide pin bolts. tighten to 32
N´m (24 ft. lbs.)
(4) Remove the prop rod.
(5) Bleed the base brake system, (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL - STAN-
DARD PROCEDURE).
(6) Install the tire and wheel assembly, (Refer to
22 - TIRES/WHEELS/WHEELS - STANDARD PRO-
CEDURE).
(7) Lower the vehicle.
INSTALLATION - REAR
(1) Install caliper to the caliper adapter.
(2) Coat the caliper mounting slide pin bolts with
silicone grease. Then install and tighten the bolts to
15 N´m (11 ft. lbs.).
(3) Install the brake hose banjo bolt if removed.
(4) Install the brake hose to the caliper withnew
seal washersand tighten fitting bolt to 27 N´m (245
in. lbs.).CAUTION: Verify brake hose is not twisted or
kinked before tightening fitting bolt.
(5) Remove the prop rod from the vehicle.
(6) Bleed the base brake system,(Refer to 5 -
BRAKES - STANDARD PROCEDURE) OR (Refer to
5 - BRAKES - STANDARD PROCEDURE).
(7) Install the wheel and tire assemblies (Refer to
22 - TIRES/WHEELS/WHEELS - STANDARD PRO-
CEDURE).
(8) Remove the supports and lower the vehicle.
(9) Verify a firm pedal before moving the vehicle.
DISC BRAKE CALIPER
ADAPTER
REMOVAL
REMOVAL - FRONT
(1) Raise and support the vehicle.
(2) Remove the tire and wheel assembly.
(3) Remove the disc brake caliper (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/DISC
BRAKE CALIPERS - REMOVAL).
(4) Remove the bolts securing the caliper adapter
to the steering knuckle (Fig. 38)
(5) Remove the caliper adapter.
REMOVAL - REAR
(1) Raise and support the vehicle.
(2) Remove the wheel and tire assembly.
(3) Drain a small amount of fluid from master cyl-
inder brake reservoir with acleansuction gun.
Fig. 37 Seating Dust Boot
1 - HANDLE
2 - CALIPER
3 - DUST BOOT INSTALLER
Fig. 38 CALIPER ADAPTER
1 - CALIPER ASSEMBLY
2 - MOUNTING BOLT
3 - DISC BRAKE ROTOR
DRBRAKES - BASE 5 - 21
DISC BRAKE CALIPERS (Continued)

(4) Bottom the caliper pistons into the caliper by
prying the caliper over.
(5) Remove the caliper slide bolts.
(6) Remove the disc brake caliper from the mount.
CAUTION: Never allow the disc brake caliper to
hang from the brake hose. Damage to the brake
hose will result. Provide a suitable support to hang
the caliper securely.
(7) Remove the inboard and outboard brake pads
(Fig. 39).
(8) Remove the anti-rattle clips (Fig. 39).
(9) Remove the caliper adapter mounting bolts
(Fig. 39).
(10) Remove the caliper adapter.
INSTALLATION
INSTALLATION - FRONT
(1) Install the caliper adapter to the steering
knuckle (Fig. 38).
(2) Install the caliper adapter mounting bolts and
tighten to 176 N´m (130 ft.lbs.) (Fig. 38).
(3) Install the disc brake caliper (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/DISC
BRAKE CALIPERS - INSTALLATION).
(4) Install the tire and wheel assembly (Refer to 22
- TIRES/WHEELS/WHEELS - STANDARD PROCE-
DURE).
(5) Remove the support and lower the vehicle.
INSTALLATION - REAR
(1) Install the caliper adapter mounting bolts.
Tighten the mounting bolts to 135 N´m (100 ft.lbs)
(Fig. 39).(2) Install the anti-rattle clips (Fig. 39).
(3) Install the inboard and outboard pads (Fig. 39).
(4) Install the caliper mounting bolts.
(5) Install the tire and wheel assembly
DISC BRAKE CALIPER
ADAPTER MOUNT
REMOVAL - REAR
(1) Remove wheel and tire assembly.
(2) Remove the disc brake caliper (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/DISC
BRAKE CALIPERS - REMOVAL).
(3) Remove the caliper adapter (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/DISC
BRAKE CALIPER ADAPTER - REMOVAL).
(4) Remove the rotor (Refer to 5 - BRAKES/HY-
DRAULIC/MECHANICAL/ROTORS - REMOVAL).
(5) Remove the axle shaft (Refer to 3 - DIFFER-
ENTIAL & DRIVELINE/REAR AXLE - 9 1/4/AXLE
SHAFTS - REMOVAL).
(6) Remove the park brake shoes (Refer to 5 -
BRAKES/PARKING BRAKE/SHOES - REMOVAL).
(7) Remove the parking brake cable from the
brake lever.
(8) Remove the bolts attaching the support plate to
the axle and remove the support plate (Fig. 65).
(9) Remove the caliper adapter mount from the
axle housing (Fig. 40).
INSTALLATION
(1) Install the caliper adapter mount on the axle
housing (Fig. 40).
(2) Install support plate on axle flange (Fig. 66).
Tighten attaching bolts to 115 N´m (85 ft. lbs.).
Fig. 39 CALIPER MOUNT
1 - DISC BRAKE PADS
2 - ANTI-RATTLE CLIPS
3 - CALIPER ADAPTER
4 - MOUNTING BOLTS
Fig. 40 CALIPER ADAPTER MOUNT - REAR
1 - CALIPER ADAPTER MOUNT
2 - AXLE TUBE
3 - MOUNTING STUDS
5 - 22 BRAKES - BASEDR
DISC BRAKE CALIPER ADAPTER (Continued)

(3) Install parking brake cable in the brake lever.
(4) Install the park brake shoes (Refer to 5 -
BRAKES/PARKING BRAKE/SHOES - INSTALLA-
TION). (Fig. 66).
(5) Install axle shaft, (Refer to 3 - DIFFEREN-
TIAL & DRIVELINE/REAR AXLE - 9 1/4/AXLE
SHAFTS - INSTALLATION).
(6) Adjust brake shoes to drum with brake gauge
(Refer to 5 - BRAKES/PARKING BRAKE/SHOES -
ADJUSTMENTS).
(7) Install the rotor (Refer to 5 - BRAKES/HY-
DRAULIC/MECHANICAL/ROTORS - INSTALLA-
TION).
(8) Install the caliper adapter (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/DISC
BRAKE CALIPER ADAPTER - INSTALLATION).
(9) Install the caliper (Refer to 5 - BRAKES/HY-
DRAULIC/MECHANICAL/DISC BRAKE CALIPERS
- INSTALLATION).
(10) Install wheel and tire assembly.
FLUID
DIAGNOSIS AND TESTING - BRAKE FLUID
CONTAMINATION
Indications of fluid contamination are swollen or
deteriorated rubber parts.
Swollen rubber parts indicate the presence of
petroleum in the brake fluid.
To test for contamination, put a small amount of
drained brake fluid in clear glass jar. If fluid sepa-
rates into layers, there is mineral oil or other fluid
contamination of the brake fluid.
If brake fluid is contaminated, drain and thor-
oughly flush system. Replace master cylinder, propor-
tioning valve, caliper seals, wheel cylinder seals,
Antilock Brakes hydraulic unit and all hydraulic
fluid hoses.
STANDARD PROCEDURE - BRAKE FLUID
LEVEL
Always clean the master cylinder reservoir and
caps before checking fluid level. If not cleaned, dirt
could enter the fluid.
The fluid fill level is indicated on the side of the
master cylinder reservoir (Fig. 41).
The correct fluid level is to the MAX indicator on
the side of the reservoir. If necessary, add fluid to the
proper level.
SPECIFICATIONS
BRAKE FLUID
The brake fluid used in this vehicle must conform
to DOT 3 specifications and SAE J1703 standards.
No other type of brake fluid is recommended or
approved for usage in the vehicle brake system. Use
only Mopar brake fluid or an equivalent from a
tightly sealed container.
CAUTION: Never use reclaimed brake fluid or fluid
from an container which has been left open. An
open container of brake fluid will absorb moisture
from the air and contaminate the fluid.
CAUTION: Never use any type of a petroleum-based
fluid in the brake hydraulic system. Use of such
type fluids will result in seal damage of the vehicle
brake hydraulic system causing a failure of the
vehicle brake system. Petroleum based fluids would
be items such as engine oil, transmission fluid,
power steering fluid, etc.
FLUID RESERVOIR
REMOVAL
(1) Install the prop rod on the brake pedal to keep
pressure on the brake system.
(2) Remove the reservoir cap and siphon fluid into
a drain container (Fig. 42).
(3) Remove the electrical connector from the fluid
level switch in the reservoir (Fig. 42).
(4) Remove the reservoir mounting bolt (Fig. 42).
Fig. 41 FLUID LEVEL TYPICAL
1 - FLUID RESERVOIR
2 - MAX LEVEL MARK
DRBRAKES - BASE 5 - 23
DISC BRAKE CALIPER ADAPTER MOUNT (Continued)

(5) Remove the reservoir from the master cylinder
by pulling upwards.
(6) Remove old grommets from cylinder body (Fig.
42).
INSTALLATION
CAUTION: Do not use any type of tool to install the
grommets. Tools may cut, or tear the grommets cre-
ating a leak problem after installation. Install the
grommets using finger pressure only.
(1) Lubricate the new grommets with clean brake
fluid and Install new grommets in cylinder body. Use
finger pressure to install and seat grommets.
(2) Start the reservoir in grommets. Then rock the
reservoir back and forth while pressing downward to
seat it into the grommets.
(3) Install the mounting bolt for the reservoir to
the master cylinder.
(4) Reconnect the electrical connector to the fluid
reservoir level switch.
(5) Remove the prop rod from the vehicle.
(6) Fill and bleed base brake system,(Refer to 5 -
BRAKES - STANDARD PROCEDURE).
BRAKE JUNCTION BLOCK
REMOVAL
(1) Remove the brake lines from the junction block
(Fig. 43).
(2) Remove the junction block mounting bolt and
remove the junction block from the bracket (Fig. 43).
INSTALLATION
(1) Position the junction block on the bracket and
install the mounting bolt. Tighten the mounting bolt
to 23 N´m (210 in. lbs.) (Fig. 43).
(2) Install the brake lines into the junction block
and tighten to 19-23 N´m (170-200 in. lbs.) (Fig. 43).
(3) Bleed the base brake system, (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL - STAN-
DARD PROCEDURE).
MASTER CYLINDER
DESCRIPTION
A two-piece master cylinder is used on all models.
The cylinder body containing the primary and sec-
ondary pistons is made of aluminum. The removable
fluid reservoir is made of nylon reinforced with glass
fiber. The reservoir stores reserve brake fluid for the
hydraulic brake circuits and has a switch for indicat-
ing low fluid levels. The reservoir is the only service-
able component.
The fluid compartments of the nylon reservoir are
interconnected to permit fluid level equalization.
However, the equalization feature does not affect cir-
cuit separation in the event of a front or rear brake
malfunction. The reservoir compartments will retain
enough fluid to operate the functioning hydraulic cir-
cuit.
Care must be exercised when removing/installing
the master cylinder connecting lines. The threads in
the cylinder fluid ports can be damaged if care is not
exercised. Start all brake line fittings by hand to
avoid cross threading.
Fig. 42 FLUID RESERVOIR
1 - MASTER CYLINDER CAP
2 - FLUID RESERVOIR
3 - FLUID LEVEL SWITCH
4 - MASTER CYLINDER
5 - MOUNTING BOLT
6 - GROMMETS
Fig. 43 JUNCTION BLOCK
1 - BRAKE LINES
2 - JUNCTION BLOCK
5 - 24 BRAKES - BASEDR
FLUID RESERVOIR (Continued)

The cylinder reservoir can be replaced when neces-
sary. However, the aluminum body section of the
master cylinder is not a repairable component.
NOTE: If diagnosis indicates that an internal mal-
function has occurred, the aluminum body section
must be replaced as an assembly.
OPERATION
The master cylinder bore contains a primary and
secondary piston. The primary piston supplies
hydraulic pressure to the front brakes. The secondary
piston supplies hydraulic pressure to the rear brakes.
DIAGNOSIS AND TESTING - MASTER
CYLINDER/POWER BOOSTER
(1) Start engine and check booster vacuum hose
connections. A hissing noise indicates vacuum leak.
Correct any vacuum leak before proceeding.
(2) Stop engine and shift transmission into Neu-
tral.
(3) Pump brake pedal until all vacuum reserve in
booster is depleted.
(4) Press and hold brake pedal under light foot
pressure. The pedal should hold firm, if the pedal
falls away master cylinder is faulty (internal leak-
age).
(5) Start engine and note pedal action. It should
fall away slightly under light foot pressure then hold
firm. If no pedal action is discernible, power booster,
vacuum supply, or vacuum check valve is faulty. Pro-
ceed to the POWER BOOSTER VACUUM TEST.
(6) If the POWER BOOSTER VACUUM TEST
passes, rebuild booster vacuum reserve as follows:
Release brake pedal. Increase engine speed to 1500
rpm, close the throttle and immediately turn off igni-
tion to stop engine.
(7) Wait a minimum of 90 seconds and try brake
action again. Booster should provide two or more vac-
uum assisted pedal applications. If vacuum assist is
not provided, booster is faulty.
POWER BOOSTER VACUUM TEST
(1) Connect vacuum gauge to booster check valve
with short length of hose and T-fitting (Fig. 44).
(2) Start and run engine at curb idle speed for one
minute.
(3) Observe the vacuum supply. If vacuum supply
is not adequate, repair vacuum supply.
(4) Clamp hose shut between vacuum source and
check valve.
(5) Stop engine and observe vacuum gauge.
(6) If vacuum drops more than one inch HG (33
millibars) within 15 seconds, booster diaphragm or
check valve is faulty.
POWER BOOSTER CHECK VALVE TEST
(1) Disconnect vacuum hose from check valve.
(2) Remove check valve and valve seal from
booster.
(3) Use a hand operated vacuum pump for test.
(4) Apply 15-20 inches vacuum at large end of
check valve (Fig. 45).
(5) Vacuum should hold steady. If gauge on pump
indicates vacuum loss, check valve is faulty and
should be replaced.
Fig. 44 Typical Booster Vacuum Test Connections
1 - TEE FITTING
2 - SHORT CONNECTING HOSE
3 - CHECK VALVE
4 - CHECK VALVE HOSE
5 - CLAMP TOOL
6 - INTAKE MANIFOLD
7 - VACUUM GAUGE
Fig. 45 Vacuum Check Valve And Seal
1 - BOOSTER CHECK VALVE
2 - APPLY TEST VACUUM HERE
3 - VALVE SEAL
DRBRAKES - BASE 5 - 25
MASTER CYLINDER (Continued)

HYDRO-BOOST BRAKE
BOOSTER
DIAGNOSIS AND TESTING - HYDRAULIC
BOOSTER
The hydraulic booster uses hydraulic pressure from
the power steering pump. Before diagnosing a
booster problem, first verify the power steering pump
is operating properly. Perform the following checks.
²Check the power steering fluid level.
²Check the brake fluid level.
²Check all power steering hoses and lines for
leaks and restrictions.
²Check power steering pump pressure.
NOISES
The hydraulic booster unit will produce certain
characteristic booster noises. The noises may occur
when the brake pedal is used in a manner not asso-
ciated with normal braking or driving habits.
HISSING
A hissing noise may be noticed when above normal
brake pedal pressure is applied, 40 lbs. or above. The
noise will be more noticeable if the vehicle is not
moving. The noise will increase with the brake pedal
pressure and an increase of system operating temper-
ature.
CLUNK-CHATTER-CLICKING
A clunk-chatter-clicking may be noticed when the
brake pedal is released quickly, after above normal
brake pedal pressure is applied 50-100 lbs..
BOOSTER FUNCTION TEST
With the engine off depress the brake pedal several
times to discharge the accumulator. Then depress the
brake pedal using 40 lbs. of force and start the
engine. The brake pedal should fall and then push
back against your foot. This indicates the booster is
operating properly.
ACCUMULATOR LEAKDOWN
(1) Start the engine, apply the brakes and turn the
steering wheel from lock to lock. This will ensure the
accumulator is charged. Turn off the engine and let
the vehicle sit for one hour. After one hour thereshould be at least two power assisted brake applica-
tion with the engine off. If the system does not retain
a charge the booster must be replaced.
(2) With the engine off depress the brake pedal
several times to discharge the accumulator. Grasp
the accumulator and see if it wobbles or turns. If it
does the accumulator has lost a gas charge and the
booster must be replaced.
SEAL LEAKAGE
If the booster leaks from any of the seals the
booster assembly must be replaced (Fig. 54).
²INPUT ROD SEAL:Fluid leakage from rear
end of the booster.
²PISTON SEAL:Fluid leakage from vent at
front of booster.
²HOUSING SEAL:Fluid leakage between hous-
ing and housing cover.
²SPOOL VALVE SEAL:Fluid leakage near
spool plug.
²RETURN PORT FITTING SEAL:Fluid leak-
age from port fitting.
Fig. 54 Hydraulic Booster Seals
1 - PUMP
2 - GEAR
3 - INPUT SEAL
4 - HOUSING SEAL
5 - ACCUMULATOR SEAL
6 - PISTON SEAL
7 - SPOOL PLUG SEAL
8 - RETURN
5 - 30 BRAKES - BASEDR