1998 ISUZU TROOPER brakes

5C – 6 POWER ASSISTED BRAKE SYSTEM
Condition Possible Cause Correction
Brake Drag1. Master cylinder pistons not returning 1. Adjust stop light switch and vacuum
correctly. booster operating rod. If necessary,
rebuild.
2. Restricted brake pipes or hoses. 2. Check for soft hoses or damaged pipes,
and replace with new hoses and new
double-walled steel brake piping.
3. Parking brake maladjusted. 3. Adjust.
4. Parking brake lining clearance 4. Adjust.
insufficient.
5. Brake pedal free play insufficient. 5. Adjust brake pedal height or power
cylinder operating rod.
6. Piston in master cylinder sticking. 6. Replace.
7. Piston in disc brake caliper sticking. 7. Replace piston seals.
8. Brake pads sticking in caliper. 8. Clean.
9. Return spring weakened. 9. Replace.
10. Parking brake binding. 10. Overhaul parking brakes and correct.
11. Front hub bearing preload incorrect. 11. Adjust or replace.
12. Parking brake shoes not returning. 12. Correct or replace brake back plate and
brake shoe as necessary.
13. Obstructions in hydraulic circuit. 13. Clean.
14. Rotor warped excessively. 14. Grind or replace.
15. Rear brake drum distorted. 15. Grind or replace.
16. Parking cable sticking. 16. Clean or replace.
Grabbing or1. Malfunctioning vacuum booster. 1. Check operation and correct as
Uneven necessary.
Braking Action 2. Binding brake pedal mechanism. 2. Check and lubricate, if necessary.
(All conditions3. Corroded caliper assembly. 3. Clean and lubricate.
listed under
“Pulls”)
Brake Noisy1. Brake pads worn. 1. Replace.
2. Brake pads hardened. 2. Replace.
3. Brake pads in poor contact with rotor. 3. Correct.
4. Brake disc(s) warped, worn or 4. Grind or replace.
damaged.
5. Disc brake anti-squeak shims fatigued. 5. Replace.
6. Front hub bearings loose or preload is 6. Adjust or replace.
incorrect.
7. Brake disc rusted. 7. Grind or replace.
Poor Brake1. Master cylinder faulty. 1. Correct or replace.
Action2. Vacuum booster faulty. 2. Correct or replace.
3. Level of brake fluid in reservoir too 3. Replenish and bleed.
low.
4. Air in hydraulic circuit. 4. Bleed.
5. Disc brake caliper faulty. 5. Clean or replace.
6. Water or oil on brake pads. 6. Clean or replace.
7. Brake pads in poor contact with rotor. 7. Correct.
8. Brake pads worn. 8. Replace.
9. Brake disc rusted. 9. Grind or replace.
10. Check valve in vacuum hose faulty. 10. Correct or replace.

POWER ASSISTED BRAKE SYSTEM 5C – 9
SERVICING
FILLING MASTER CYLINDER RESERVOIR
CAUTION:
1) Use only specified brake fluid. Do not use any
fluid which contains a petroleum base. Do not
use a container which has been used for
petroleum based fluids or a container which is
wet with water. Petroleum based fluids will
cause swelling and distortion of rubber parts in
the hydraulic brake system. Water mixed with
brake fluid lowers the fluid boiling point. Keep all
fluid containers capped to prevent
contamination.
2) Always fill the master cylinder reservoid when
the engine is cold.
3) Never allow the brake fluid to come in contact
with the painted surfaced.
The master cylinder reservoir must be kept properly
filled to ensure adequate reserve and to prevent air
and moisture from entering the hydraulic system.
However, because of expansion due to heat absorbed
from the brakes and the engine, the reservoir must not
be overfilled. The brake fluid reservoir is on the
master cylinder, which is located under the hood on
the driver side of the cowl. Thoroughly clean reservoir
cap before removal to avoid getting dirt into reservoir.
Remove cap and diaphragm. Add fluid as required to
bring level to the “MAX” mark on the reservoir tank.
Use “DOT 3“ Hydraulic Brake Fluid. If the fluid cap
diaphragm is stretched, return it to the original
position before installing.
DETERIORATION OF BRAKE FLUID
Using any other brake fluid than speficied or brake
fluid with mineral oil or water mixed in will drop the
boiling point of brake fluid. It may, in turn, reuslt in
vapor lock or deteriorated rubber parts of the
hydraulic system. Be sure to change brake fluid at
specified intervals.
If rubber parts are deteriorated, remover all the
system parts and clean them with alcohol. Prior to
reassembly, dry the cleaned parts with air to remove
the alcohol. Replace all hoses and rubber parts of the
system.
LEAKAGE OF BRAKE FLUID
With engine idling, set shift lever in the neutral
position and continue to depress brake pedal at a
constant pedal application force.
Should the pedal stroke become deeper gradually,
leak from the hydraulic pressure system is possible.
Make sure by visual check that there is no leak.

5C – 10 POWER ASSISTED BRAKE SYSTEM
BLEEDING BRAKE HYDRAULIC SYSTEM
A bleeding operation is necessary to remove air from
the hydraulic brake system whenever air is introduced
into the hydraulic system. It may be necessary to
bleed the hydraulic system at all four brakes if air has
been introduced through a low fluid level or by
disconnecting brake pipes at the master cylinder. If a
brake pipe is disconneted at one wheel, only that
wheel cylinder/caliper needs to be bled. If pipes are
disconnected at any fitting located between master
cylinder and brakes, then the brake system served by
the disconnected pipe must be bled.
1. For 4-wheel Antilock Brake System (ABS)
equipped vehicle, be sure to remove the ABS main
fuse 40A located at the relay and fuse box before
bleeding air. If you attempt to bleed air without
removing the main fuse, air cannot be let out
thoroughly, and this may cause damage to the
hydraulic unit. After bleeding air, be sure to
replace the ABS main fuse back to its original
position.
2. Set the parking brake completely, then start the
engine.
NOTE:
The vacuum booster will be damaged if the bleeding
operation is performed with the engine off.
3. Remove the master cylinder reservoir cap.
4. Fill the master cylinder reservoir with brake fluid.
Keep the reservoir at least half full during the air
bleeding operation.
5. Always use new brake fluid for replenishment.
6. In replenishing brake fluid, take care that air
bubbles do not enter the brake fluid.
•When the master cylinder is replaced or
overhauled, first bleed the air from the master
cylinder, then from each wheel cylinder and
caliper following the procedures described
below.
Bleeding the Master Cylinder
7. Disconnect the rear wheel brake pipe 1from the
master cylinder. Check the fluid level and
replenish as necessary. If replenished, leave the
system for at least one minute.
8. Depress the brake pedal slowly once and hold it
depressed.
9. Completely seal the delivery port of the master
cylinder where the pipe was disconnected with
your finger, then release the brake pedal slowly.
10. Release your finger from the delivery port when
the brake pedal returns completely.
11. Repeat steps 7 through 9 until the brake fluid
comes out of the delivery port during step 7.
NOTE:
Do not allow the fluid level in the reservoir to go
below the half-way mark.
21

POWER ASSISTED BRAKE SYSTEM 5C – 15
CHECKING LATERAL RUNOUT
1. Adjust the wheel bearing correctly.
•Refer to Front Hub and Disc in Driveline / Axle
Section.
2. Attach a dial indicator to some portion of the
suspension so that the stem contacts the rotor
face about 29 mm (1.14 in) from the rotor edge.
3. Move the rotor one complete rotation.
•The lateral runout should not exceed 0.13 mm
(0.005 in).
Maximum Runout mm (in)
0.13 (0.005)
PARALLELISM
Parallelism is the measurement of the thickness of the
rotor at four or more points around the circumference
of the rotor. All measurement must be made at 29 mm
(1.14 in) from the edge of the rotor.
The rotor thickness must not vary more than 0.010
mm (0.004 in) from point to point.
Maximum Parallelism mm (in)
0.010 (0.0004)
REPLACING FRONT BRAKE ROTORS
When installing new brake rotors, do not refinish the
surfaces. These parts are at the correct level of surface
finish.
REFINISHING FRONT BRAKE ROTORS
Accurate control of the rotor tolerances is necessary
for proper performance of the disc brakes. Machining
of the rotor should be done only with precision
equipment. All brake rotors have a minimum
thickness dimension cast into them. This dimension is
the minimum wear dimension and not a refinish
dimension. The minimum wear dimension is 24.60
mm (0.969 in). The minimum refinish dimension is
24.97 mm (0.983 in).
When refinishing rotors, always use sharp cutting
tools or bits. Dull or worn tools leave a poor surface
finish which will affect initial braking performance.
Vibration dampening attachments should always be
used when refinishing braking surfaces. These
attachments eliminate tool chatter and will result in
better surface finish.
After refinishing, replace any rotor that does not meet
the minimum thickness of 24.97 mm (0.983 in). Do not
use a brake rotor that will not meet the specification.
Minimum Wear Dimension mm (in)
24.60 (0.969)
Refinish Dimension mm (in)
24.97 (0.983)
t

5C – 16 POWER ASSISTED BRAKE SYSTEM
PARALLELSIM
Parallelism is the measurement of the thickness of the
rotor at four or more points around the circumference
of the rotor. All measurements must be made at 22 mm
(0.87 in) from the edge of the rotor.
The rotor thickness must not vary more than 0.010
mm (0.0004 in) from point to point.
Maximum Parallelism Variation mm (in)
0.010 (0.0004)
REPLACING REAR BRAKE ROTORS
When installing new brake rotors, do not refinish the
surfaces. These parts are at the correct level of surface
finish.
REFINISHING REAR BRAKE ROTORS
Accurate control of the rotor tolerances is necessary
for proper performance of the disc brakes. Machining
of the rotor should be done only with precision
equipment. All brake rotors have a minimum
thickness dimension cast into them. This dimension is
the minimum wear dimension and not a refinish
dimension. The minimum wear dimension is 16.60
mm (0.654 in). The refinish dimension is 16.97 mm
(0.668 in).
When refinishing rotors, always use sharp cutting
tools or bits. Dull or worn tools leave a poor surface
finish which will affect initial braking performance.
SERVICING THE REAR BRAKE ROTOR
In the manufacturing of the rear brake rotor, all the
tolerances regarding surface finish, parallelism and
lateral runout are held very closely. The maintenance
of these tolerances provide the surface necessary to
assure smooth brake operation.
LATERAL RUNOUT
Lateral runout is the movement of the rotor from side
to side as it rotates on the spindle. This could also be
referred to as “rotor wobble”.
This movement causes the piston to be knocked back
into its bore. This results in additional pedal travel and
a vibration during braking.
CHECKING LATERAL RUNOUT
1. Attach a dial indicator to some portion of the
suspension so that the stem contacts the rotor
face about 22 mm (0.87 in) from the rotor edge.
2. Move the rotor one complete rotation.
•The lateral runout should not exceed 0.13 mm
(0.005 in).
Maximum Runout mm (in)
0.13 (0.005)
t

5C – 20 POWER ASSISTED BRAKE SYSTEM
Front and Rear Brakes N·m (kg·m/lb·ft)
74(7.5/54) Front disc brake
Rear disc brake
35(3.6/26)
74(7.5/54)155(15.8/115)
35(3.6/26)
104(10.6/77)
44(4.5/32)
8(0.8/69 Ib
Kin)
8(0.8/69 Ib
Kin)

5C – 22 POWER ASSISTED BRAKE SYSTEM
GENERAL DESCRIPTION
MASTER CYLINDER
The master cylinder contains two pistons that supply
the hydraulic pressure for a dual-circuit braking
system. The primary piston provides the fluid
pressure to the front brakes, while the secondary
piston provides the fluid pressure to the rear brakes.
If the pressure is lost from either system, the
remaining system will function to stop the vehicle.
CAUTION:
1) The master cylinder is not repairable. If found
defective, it must be replaced as complete
assembly.
2) If any hydraulic component is removed or
disconneted, it may be necessary to bleed all or
part of the brake system.
3) The torque values specified are for dry,
unlubricated fasteners.
4) Perform service operations on a clean bench free
from all mineral oil materials.
330RW013

POWER ASSISTED BRAKE SYSTEM 5C – 23
VACUUM BOOSTER
This booster is a tandem vacuum unit with a diaphragm effective diameter 205 mm + 230 mm (gasoline
engine model) / 180 mm + 205 mm (diesel engine model). In normal operating mode, with the service
brakes in the released position, the tandem vacuum booster operates with vacuum on both sides of its
diaphragms. When the brakes are applied, air at atmospheric pressure is admitted to one side of each
diaphragm to provide the power assist. When the service brake is released, the atmospheric air is shut
off from the one side of each diaphragm. The air is then drawn from the booster through the vacuum
check valve to the vacuum source.
CAUTION:
1) If any hydraulic component is removed or disconnected, it may be necessary to bleed all or part of
the brake system.
2) The torque values specified are for dry, unlubricated fasteners.
3) The vacuum booster is not repairable and must be replaced as complete assembly.