Isuzu N-Series. Manual — part 197

SERVICE INFORMATION 00-5

Low Pedal or Pedal
Goes to Floor

1. Excessive clearance between the lin-

ings and drum.

1. Adjust the brakes.

2. Pedal stop not adjusted, or missing.

2. Adjust or install the pedal stop.

3. Weak brake hose.

3. Replace with new hose.

4. Leaking wheel cylinder.

4. Clean and rebuild.

5. Air in the hydraulic system.

5. Bleed the hydraulic system.

6. Improper brake fluid (low boiling point).

6. Flush the system and refill with recom-

mended brake fluid.

7. Low fluid level.

7. Fill the reservoir with brake fluid; check

for leaks and bleed system.

8. Bent or distorted brake shoes.

8. Replace in axle sets.

9. Leaks at hydraulic line connections.

9. Check for hydraulic leaks and repair.

Slow Brake Release

1. Foot pedal binding.

1. Lubricate the pivot pin; clean-check for

foreign objects.

2. Restriction in the line.

2. Remove the restriction or replace line.

3. Weak shoe return spring.

3. Replace the spring.

Poor Assist or Loss of
Assit

1. Low brake fluid level.

1. Fill the reservoir to the proper level.

Bleed the system.

2. Air in the hydraulic system.

2. Locate the source of the air leak and re-

pair. Bleed the system.

3. Weak brake hose.

3. Replace.

4. Loss of vacuum.

4. Inspect for vacuum leaks or malfunc-

tioning pump. Repair or replace as nec-
essary.

5. No brake fluid at the master cylinder.

5. Check for plugged, kinked, or damaged

hose to the reservoir.

Brake Fade

1. Incorrect lining/pad.

1. Replace with recommended lining/pad.

2. Poor lining/pad contact.

2. Grind the lining/pad to the proper radi-

us; adjust.

3. Thin drum.

3. Replace the drum.

4. Dragging brakes.

4. Adjust.

5. All conditions listed under “Pulls to One

Side”.

5. All corrections listed under “Pulls to

One Side”.

All Brakes Drag when
Adjustment is Known
to be Correct

1. Pedal does not return to stop.

1. Lubricate the pedal linkage; adjust the

pedal.

2. Improper fluid.

2. Replace rubber parts and fill with the

recommended brake fluid.

3. Use of incorrect rubber parts.

3. Install the proper parts.

PROBLEM

POSSIBLE CAUSE

CORRECTION

00-6 SERVICE INFORMATION

One Wheel Drags

1. Weak or broken shoe return spring.

1. Replace the return spring.

2. Brake shoe to drum clearance too

small.

2. Adjust to specification.

3. Loose wheel bearings.

3. Adjust or replace the wheel bearings.

4. Wheel cylinder piston cups swollen and

distorted or piston stuck.

4. Rebuild the cylinders. Flush the hydrau-

lic system and fill with recommended
fluid.

5. Pistons sticking in the wheel cylinder.

5. Clean or replace the pistons; clean the

cylinder bore.

6. Drum out-of-round.

6. Machine the drum.

7. Disc warped.

7. Machine the disc.

8. Restricted brake line or hose.

8. Check for soft hoses or damaged lines.

Replace as necessary.

9. Distorted shoe.

9. Replace.

10. Defective lining/pad.

10. Replace with the recommended lining/

pad.

11. Loose or bent mounting plate.

11. Tighten the fasteners; replace the plate.

12. Loose calipers.

12. Tighten the fasteners.

Dragging Brakes

1. Improper fluid.

1. Flush the hydraulic system and fill with

recommended brake fluid, and replace
rubber components.

2. Brake pedal adjustment incorrect.

2. Adjust the pedal.

3. Incorrect shoe return spring.

3. Replace the shoe return spring.

4. Brake pedal linkage interference or

binding.

4. Free the linkage and lubricate.

5. Incorrect lining/pad.

5. Replace the linings/pads.

6. All conditions listed under “One Wheel

Drags”.

6. All corrections under “One Wheel

Drags”.

PROBLEM

POSSIBLE CAUSE

CORRECTION

SERVICE INFORMATION 00-7

Hydraulic Booster

PROBLEM

POSSIBLE CAUSE

CORRECTION

Large force pressing
on the brake pedal
(boosting insufficient)

1. Booster operation insufficient

• Large internal leakage
• Sticking of the spool valve
• Insufficient sliding around the input

and output rods

• With the engine on, press the brake

pedal repeatedly, and confirm the pres-
ence of manual operation.
With regard to manual operation, turn
the engine off, and judge whether the
pedal is as stiff and its play is as small
as when the pedal is pressed repeated-
ly ten times or more.

• When there is manual operation, the

hydro boost assembly is replaced.

Brake dragging

1. Bad dimensions of the booster

• The amount of protrusion of the out-

put rod is large

• Confirm whether the amount of protru-

sion of the output rod (the distance from
surface of the master cylinder attach-
ment flange to the end of the rod) is no
greater than 18.2 mm (0.717 in).

• If the above dimension is outside the

range, replace the hydro boost assem-
bly.

2. Bad pedal circumference attachment

dimensions

• Clevis position dimension is large

• Confirm whether the clevis position di-

mension (the distance from surface of
the vehicle attachment flange to the
center of the clevis center) is in the
range 109

± 1 mm (4.29 ± 0.04 in).

• If the above dimension is outside the

range, loosen the lock nut and adjust
the clevis position dimension to be in-
side the above range.
After making this adjustment, be sure to
securely tighten the lock nut and to do a
stop light switch reconfirmation.

3. Booster return is bad

• Input-output rod circumference

sticks

• Bad spool valve operation

• With the engine on, repeatedly press

the brake pedal and confirm the pedal
return state.

• If the pedal does not return, replace the

hydro boost assembly as necessary.

Oil leakage

1. Hydro boost assembly external leakage

• Leakage from the seal material

• If the oil leakage is caused by loose-

ness in the piping connections, retight-
en the connections.

• If there is oil leakage from the connec-

tions of the accumulator, replace the af-
fected seals of the connections with
new seals.

• If there is any oil leakage from parts oth-

er than the above that are included in
the hydro boost assembly, replace the
hydro boost assembly or the repair set-
ting parts (accumulator).

00-8 SERVICE INFORMATION

Bad brake operation
(lack of smoothness in
operation)

1. Poor operation of the booster

• Input-output rod circumference

sticks

• Bad spool valve operation

• With the engine on, repeatedly press

the brake pedal and confirm the pedal
operation state.

• If there is sticking or some other abnor-

mality in the pedal operation, replace
the hydro boost assembly as neces-
sary.

Abnormal brake noise
(when pressing the
pedal)

1. Air in the hydraulic booster lines

• With the engine running, check the

amount of hydraulic fluid remaining in
the reserve tank for the hydraulic boost-
er.

• If low, add fluid (Besco ATF III) and

bleed to remove air as necessary be-
fore starting the engine.
Operate the pump and repeatedly step
on the pedal to confirm the gear noise
(caused by cavitation).

2. Water in the hydraulic fluid

• Check the color of the hydraulic fluid in

the reserve tank for the hydraulic boost-
er (normal: purple, abnormal: milky
white).

• If the hydraulic fluid is milky white,

change the fluid (Besco ATF III) and
bleed to remove air as necessary be-
fore starting the engine. Operate the
pump and strongly press the pedal until
reaching full boost range to confirm the
gear noise (caused by cavitation).
The length of time to keep the pedal
pressed all the way down is no more
than five seconds.

No pedal boosting
effect immediately after
turning the engine off

1. Faulty charge valve

• Gas leaking from the accumulator
• Leakage inside the charge valve

• Keep the engine running for more than

10 seconds. Turn off the engine, and
within 60 seconds, step on the pedal
once to confirm boosting effect.
Boosting effect means the same pedal
effort if the engine was running.

• If boosting effect does not exist, either

the hydraulic booster assembly or the
accumulator may need to be replaced.

PROBLEM

POSSIBLE CAUSE

CORRECTION

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Текст

Политика конфиденциальности