Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Manual - part 1185

POWER-ASSISTED BRAKE SYSTEM

5C–7

General Diagnosis

Condition

Possible cause

Correction

Brake Pull

Tire inflation pressure is unequal.

Adjust

Front wheel alignment is incorrect.

Adjust

Unmatched tires on same axle.

Tires with approx. the same amount
of tread should be used on the same
axle.

Restricted brake pipes or hoses.

Check  for  soft  hoses  and  damaged
lines. Replace with new hoses and
new double walled steel brake
piping.

Water or oil on the brake pads.

Clean or replace.

Brake pads hardened.

Replace

Brake pads worn excessively.

Replace

Brake rotor worn or scored.

Grind or replace.

Disc brake caliper malfunctioning.

Clean or replace.

Front hub bearing preload incorrect.

Adjust or replace.

Loose suspension parts.

Check all suspension mountings.

Loose 

calipers.

Check and tighten the bolts to
specifications.

Brake Roughness or Chatter
(Pulsates)

Excessive lateral runout.

Check per instructions. If not within
specifications, replace or machine
the rotor.

Parallelism not within specifications.

Check per instructions. If not within
specifications, replace or machine
the rotor.

Pad reversed (steel against iron).

Replace the brake pad and machine
rotor to within specifications.

Excessive 

Pedal 

Effort

Malfunctioning 

vacuum 

booster.

Check the vacuum booster
operation and repair, if necessary.

Partial 

system 

failure.

Check the front and rear brake
system for failure and repair. Also,
check the brake warning light. If a
failed system is found, the light
should indicate failure.

Excessively worn pad.

Check and replace pads in sets.

Piston in caliper stuck or sluggish.

Remove caliper and rebuild.

Fading brakes due to incorrect pad.

Remove  and  replace  with  original
equipment pad or equivalent.

Vacuum leak to vacuum booster.

Check for ruptured or loose hose.

Check the direction of check valve
within vacuum hose.

Correct vacuum hose direction.

Grease on the brake pads.

Replace or clean.

5C–8

POWER-ASSISTED BRAKE SYSTEM

Excessive Brake Pedal Travel

Air in hydraulic circuit.

Bleed the hydraulic circuit.

Level of brake fluid in the reservoir
too low.

Replenish brake fluid reservoir to
specified level and bleed hydraulic
circuit as necessary.

Master cylinder push rod clearance
excessive.

Adjust

Leakage in hydraulic system.

Correct or replace defective parts.

Brake Drag

Master cylinder pistons not returning
correctly.

Adjust the stop light switch and
vacuum booster push rod. If
necessary, rebuild.

Restricted brake pipes or hoses.

Check for soft hoses or damaged
pipes, and replace with new hoses
and new double–walled steel brake
piping.

Parking brake maladjusted.

Adjust

Parking brake lining clearance
insufficient.

Adjust

Brake pedal free play insufficient.

Adjust the brake pedal height or
power cylinder operating rod.

Piston in the master cylinder
sticking.

Replace

Piston in the disc brake caliper
sticking.

Replace piston seals.

Brake pads sticking in caliper.

Clean

Return spring weakened.

Replace

Parking brake binding.

Overhaul  the  parking  brakes  and
correct.

Front hub bearing preload incorrect.

Adjust or replace.

Parking brake shoes not returning.

Correct or replace the brake back
plate and brake shoe as necessary. 

Obstructions in hydraulic circuit.

Clean

Rotor warped excessively.

Grind or replace.

Rear brake drum distorted.

Grind or replace.

Parking cable sticking.

Grind or replace.

Grabbing or Uneven Braking Action
(All conditions listed under “Pulls”)

Malfunctioning 

vacuum 

booster.

Check operation and correct as
necessary.

Binding brake pedal mechanism.

Check and lubricate, if necessary.

Corroded caliper assembly.

Clean and lubricate.

Condition

Possible cause

Correction

POWER-ASSISTED BRAKE SYSTEM

5C–9

Brake Noisy

Brake pads are worn.

Replace

Brake pads are hardened.

Replace

Brake pads are in poor contact with
rotor.

Correct

Brake disc(s) warped, worn or
damaged.

Grind or replace.

Disc brake anti–squeak shims
fatigued.

Replace

Front hub bearings are loose or
preload is incorrect.

Adjust or replace.

Brake disc is rusted.

Grind or replace.

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.

Condition

Possible cause

Correction

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
engine 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
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 left side of the cowl.
Thoroughly clean reservoir cap before removal to
avoid getting dirt into reservoir. 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.