Hydraulic Brakes; Filling Master Cylinder Reservoir; Deterioration Of Brake Fluid; Leakage Of Brake Fluid - Isuzu 2000 Trooper Workshop Manual

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 cup and diaphragm. Add fluid as re-
quired 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, a
leakage from the hydraulic pressure system is possible.
Make sure by visual check that there is no leak.

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
cylinder/caliper needs to be bled. If the pipes are
disconnected at any fitting located between the master

Hydraulic Brakes

wheel, only that wheel
POWER ASSISTED BRAKE SYSTEM
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 (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 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.
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.
5C–9