Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Manual - part 173

5C–9

POWER–ASSISTED BRAKE SYSTEM

Condition

Correction

Possible cause

Poor Brake Action

Master cylinder faulty.

Correct or replace.

Vacuum booster faulty.

Correct or replace.

Level of brake fluid in reservoir too
low.

Replenish and bleed.

Air in hydraulic circuit.

Bleed

Disc brake caliper faulty.

Clean or replace.

Water or oil on brake pads.

Clean or replace.

Brake pads in poor contact with the
rotor.

Correct

Brake pads worn.

Replace

Brake disc rusted.

Grind or replace.

Check valve in vacuum hose faulty.

Correct or replace.

5C–10 POWER–ASSISTED BRAKE SYSTEM

Hydraulic Brakes

Filling Master Cylinder Reservoir

CAUTION: 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 fluid 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.
Always fill the master cylinder reservoir when the en-
gine is cold.
Never allow the brake fluid to come in contact with
the painted surfaces.
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 ab-
sorbed 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 left side of the cowl. Thoroughly clean reser-
voir cap before removal to avoid getting dirt into res-
ervoir. Remove the 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 specified or brake fluid
with mineral oil or water mixed in will drop the boiling point
of brake fluid. It may, in turn, result in vapor lock or
deteriorated rubber parts of the hydraulic system. Be sure
to change the brake fluid at specified intervals.
If the rubber parts are deteriorated, remove all the system
parts and clean them with alcohol. Prior to reassembly,
dry the cleaned parts with air to remove the alcohol.
Replace all the 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,
leakage from the hydraulic pressure system is possible.
Perform visual inspection for any signs of leakage.

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
disconnected at one wheel, only that wheel
cylinder/caliper needs to be bled. If the pipes are

disconnected at any fitting located between the 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 60A
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. When replenishing the brake fluid reservoir, carefully

pour in the brake fluid to prevent air bubbles from
entering the brake system.
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 (1) from 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 with your finger, where the pipe was
disconnected then release the brake pedal slowly.

10. Release your finger from the delivery port when the

brake pedal returns completely.

11. Repeat steps 8 through 10 until the brake fluid comes

out of the delivery port during step 8.

NOTE: Do not allow the fluid level in the reservoir to go
below the half–way mark.

12. Reconnect the brake pipe (1) to the master cylinder

and tighten the pipe.

13. Depress the brake pedal slowly once and hold it

depressed.

14. Loosen the rear wheel brake pipe (1) at the master

cylinder.

15. Retighten the brake pipe, then release the brake

pedal slowly.

16. Repeat steps 13 through 15 until no air comes out of

the port when the brake pipe is loosened

NOTE: Be very careful not to allow the brake fluid to come
in contact with painted surfaces.

5C–11

POWER–ASSISTED BRAKE SYSTEM

330RW012

17. Bleed the air from the front wheel brake pipe

connection (2) by repeating steps 7 through 16.

Bleeding the Caliper

18. Bleed the air from each wheel in the order listed

below:

D

Right rear caliper or wheel cylinder

D

Left rear caliper or wheel cylinder

D

Right front caliper

D

Left front caliper

Conduct air bleeding from the wheels in the above
order. If no brake fluid comes out, it suggests that air
is mixed in the master cylinder. In this case, bleed air
from the master cylinder in accordance with steps 7
through 17, and then bleed air from the caliper or
wheel cylinder.

19. Place the proper size box end wrench over the

bleeder screw.

20. Cover the bleeder screw with a transparent tube, and

submerge the free end of the transparent tube in a
transparent container containing brake fluid.

21. Pump the brake pedal slowly three (3) times

(once/sec), then hold it depressed.

22. Loosen the bleeder screw until fluid flows through the

tube.

23. Retighten the bleeder screw.
24. Release the brake pedal slowly.
25. Repeat steps 21 through 24 until the air is completely

removed.
It may be necessary to repeat the bleeding procedure
10 or more times for front wheels and 15 or more
times for rear wheels.

26. Go to the next wheel in the sequence after each wheel

is bled. 
Be sure to monitor reservoir fluid level.

27. Depress the brake pedal to check if you feel

“sponginess” after the air has been removed from all
wheel cylinders and calipers. 
If the pedal feels “spongy”, the entire bleeding
procedure must be repeated.

28. After the bleeding operation is completed on the each

individual wheel, check the level of the brake fluid in
the reservoir and replenish up to the “MAX” level as
necessary.

29. Attach the reservoir cap.

If the diaphragm inside the cap is deformed, reform
it and install.

30. Stop the engine.

Flushing Brake Hydraulic System

It is recommended that the entire hydraulic system be
thoroughly flushed with clean brake fluid whenever new
parts are installed in the hydraulic system.  Approximately
one quart of fluid is required to flush the hydraulic system.
The system must be flushed if there is any doubt as to the
grade of fluid in the system or if fluid has been used which
contains the slightest trace of mineral oil. All rubber parts
that have been subjected to a contaminated fluid must be
replaced.

Brake Pipes and Hoses

The hydraulic brake system components are
interconnected by special steel piping and flexible hoses.
Flexible hoses are used between the frame and the front
calipers, the frame and rear axle case and the rear axle
and the rear calipers.
When the hydraulic pipes have been disconnected for
any reason, the brake system must be bled after
reconnecting the pipe. Refer to 

Bleeding the Brake

Hydraulic System in this section.

Brake Hose Inspection

The brake hose should be inspected at least twice a year.
The brake hose assembly should be checked for road
hazard, cracks and chafing of the outer cover, and for
leaks and blisters. Inspect for proper routing and
mounting of the hose. A brake hose that rubs on
suspension components will wear and eventually fail. A
light and mirror may be needed for an adequate
inspection.  If any of the above conditions are observed on
the brake hose, adjust or replace the hose as necessary.

CAUTION: Never allow brake components such as
calipers to hang from the brake hoses, as damage to
the hoses may occur.

5C–12 POWER–ASSISTED BRAKE SYSTEM

Front Caliper Brake Hose

Front Caliper Brake Hose and
Associated Parts

352RW001

Legend

(1) Bolt and Gasket
(2) Clip
(3) Hose
(4) Brake Pipe

Removal

1. Raise the vehicle and support it with suitable safety

stands.

2. Remove the wheel and tire assembly.
3. Clean dirt, grease, and other foreign material off the

hose fittings at both ends.

4. Disconnect brake pipe.
5. Remove clip.
6. Remove bolt and gasket.
7. Remove hose.

Installation

To install, follow the removal steps in the reverse order,
noting the following points.

1. Tighten the brake pipes to the specified torque

Torque: 19 N·m (14 lb ft)

2. Tighten the bolt to the specified torque.

Torque: 35 N·m (26 lb ft)

NOTE: Always use new gaskets and be sure to put the
hooked edge of the flexible hose end into the anti–rotation
cavity.
After installing the brake hoses, bleed the brakes as
described in this section.