Brake System Testing; Brake Hose Inspection - Daewoo MATIZ Service Manual

4A – 4 HYDRAULIC BRAKES
DIAGNOSITIC INFORMATION AND PROCEDURES

BRAKE SYSTEM TESTING

(Left–Hand Drive Shown, Right–Hand
Drive Similar)
Brakes should be tested on a dry, clean, reasonably
smooth and level roadway. A true test of brake perfor-
mance cannot be made if the roadway is wet, greasy, or
covered with loose dirt whereby all tires do not grip the
road equally. Testing will also be adversely affected if the
roadway is crowned so as to throw the weight so roughly
that the wheels tend to bounce.
Test the brakes at different vehicle speeds with both light
and heavy pedal pressure; however, avoid locking the
brakes and sliding the tires. Locked brakes and sliding
tires do not indicate brake efficiency since heavily
braked, but turning, wheels will stop the vehicle in less
distance than locked brakes. More tire-to-road friction is
present with a heavily braked, turning tire than with a
sliding tire.
Because of the high deceleration capability, a firmer
pedal may be felt at higher deceleration levels.
There are three major external conditions that affect
brake performance:
D Tires having unequal contact and grip of the road will
cause unequal braking. Tires must be equally in-
flated, and the tread pattern of the right and the left
tires must be approximately equal.
D Unequal loading of the vehicle can affect the brake
performance since the most heavily loaded wheels
require more braking power, and thus more braking
effort, than the others.
D Misalignment of the wheels, particularly conditions of
excessive camber and caster, will cause the brakes
to pull to one side.
To check for brake fluid leaks, hold constant foot pres-
sure on the pedal with the engine running at idle and the
shift lever in NEUTRAL. If the pedal gradually falls away
with the constant pressure, the hydraulic system may be
leaking. Perform a visual check to confirm any sus-
pected leaks.
Check the master cylinder fluid level. While a slight drop
in the reservoir level results from normal lining wear, an
abnormally low level indicates a leak in the system. The
hydraulic system may be leaking either internally or ex-
ternally. Refer to the procedure below to check the mas-
ter cylinder. Also, the system may appear to pass this
test while still having a slight leak. If the fluid level is nor-
mal, check the vacuum booster pushrod length. If an in-
correct pushrod length is found, adjust or replace the
rod.
Check the master cylinder using the following proce-
dure:
D Check for a cracked master cylinder casting or brake
fluid leaking around the master cylinder. Leaks are in-
dicated only if there is at least one drop of fluid. A
damp condition is not abnormal.
D Check for a binding pedal linkage and for an incorrect
pushrod length. If both of these parts are in satisfac-
tory condition, disassemble the master cylinder and
check for an elongated or swollen primary cylinder or
piston seals. If swollen seals are found, substandard
or contaminated brake fluid should be suspected. If
contaminated brake fluid is found, all the components
should be disassembled and cleaned, and all the rub-
ber components should be replaced. All of the pipes
must also be flushed.
Improper brake fluid, or mineral oil or water in the fluid,
may cause the brake fluid to boil or cause deterioration
of the rubber components. If the primary piston cups in
the master cylinder are swollen, then the rubber parts
have deteriorated. This deterioration may also be evi-
denced by swollen wheel cylinder piston seals on the
drum brake wheels.
If rubber deterioration is evident, disassemble all the hy-
draulic parts and wash the parts with alcohol. Dry these
parts with compressed air before reassembly to keep al-
cohol out of the system. Replace all the rubber parts in
the system, including the hoses. Also, when working on
the brake mechanisms, check for fluid on the linings. If
excessive fluid is found, replace the linings.
If the master cylinder piston seals are in satisfactory
condition, check for leaks or excessive heat conditions.
If these conditions are not found, drain the fluid, flush the
master cylinder with brake fluid, refill the master cylin-
der, and bleed the system. Refer to "Manual Bleeding
the Brakes" in this section.

BRAKE HOSE INSPECTION

The hydraulic brake hoses should be inspected at least
twice a year. The brake hose assembly should be
checked for road hazard damage, cracks, chafing of the
outer cover, and for leaks or blisters. Inspect the hoses
for proper routing and mounting. A brake hose that rubs
on a suspension component will wear and eventually
fail. A light and a 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 neces-
sary.
DAEWOO M-150 BL2