Daewoo Nubira. Manual - part 53

HYDRAULIC BRAKES  4A – 19

DAEWOO V–121 BL4

GENERAL DESCRIPTION

AND SYSTEM OPERATION

HYDRAULIC FLUID

Brake fluid should meet the DOT–3 specification. Use
DOT–4 fluid for heavy duty applications such as trailer
towing or mountain driving. Use only clean fluid from a
sealed container. Fluid exposed to air will absorb moisture
from the air. Water in the brake fluid will cause the fluid to
boil, and the rubber components to deteriorate.

Thoroughly cleanthemaster cylinder reservoir capbefore
removing it. Do not let any dirt or foreignmaterial fall into
thefluidreservoir.

There is a fluid level switch in the master cylinder reservoir.
When the fluid level is low, the BRAKE lamp in the instru-
ment cluster will turn on. The correct brake fluid level is
marked on the driver’s side of the master cylinder reser-
voir. If the fluid level is below the MIN indicator mark, check
the hydraulic brake system for leaks and then refill the res-
ervoir to the MAX indicator mark.

SECTION : 4B

MASTER CYLINDER

CAUTION :  Disconnect the negative battery cable before removing or installing any electrical unit or when a tool
or equipment could easily come in contact with exposed electrical terminals. Disconnecting this cable will help
prevent personal injury and damage to the vehicle. The ignition must also be in LOCK unless otherwise noted.

TABLE OF CONTENTS

SPECIFICATIONS

4B–1

. . . . . . . . . . . . . . . . . . . . . . . . . . 

FASTENER TIGHTENING SPECIFICATIONS

4B–1

. 

DIAGNOSIS

4B–1

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

CHECKING BRAKE PROPORTIONING VALVE 4B–1

MAINTENANCE AND REPAIR

4B–3

. . . . . . . . . . . . . . . 

ON–VEHICLE SERVICE

4B–3

. . . . . . . . . . . . . . . . . . . . . 

MASTER CYLINDER ASSEMBLY

4B–3

. . . . . . . . . . . 

BRAKE FLUID RESERVOIR

4B–5

. . . . . . . . . . . . . . . . 

PROPORTIONING VALVE

4B–7

. . . . . . . . . . . . . . . . . . 

UNIT REPAIR

4B–8

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

MASTER CYLINDER OVERHAUL

4B–8

. . . . . . . . . . . 

GENERAL DESCRIPTION AND SYSTEM

OPERATION

4B–11

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

MASTER CYLINDER

4B–11

. . . . . . . . . . . . . . . . . . . . . 

PROPORTIONING VALVE

4B–11

. . . . . . . . . . . . . . . . . 

FLUID LEVEL SENSOR

4B–11

. . . . . . . . . . . . . . . . . . . 

SPECIFICATIONS

FASTENER TIGHTENING SPECIFICATIONS

Application

N

S

m

Lb–Ft

Lb–In

Brake Lines

16

12

–

Master Cylinder Attaching Nuts

18

13

–

Proportioning Valves

22

16

–

DIAGNOSIS

CHECKING BRAKE
PROPORTIONING VALVE

Use two brake pressure gauges to check the brake pro-
portioning valves that are attached to the master cylinder
on non–ABS braking systems. These valves limit the out-
let pressure to the rear brakes after a predetermined mas-
ter cylinder pressure has been reached. (On ABS braking
systems, the hydraulic modulator/ motor pack assembly
controls the hydraulic pressure to both the rear wheel cyl-
inders or rear calipers, and the front calipers.)

When checking the brake proportioning valves, be sure
that the hydraulic line pressure is measured simulta-
neously and diagonally on the front and the rear axles. To
measure the pressure, use the following steps.

1.  Remove the bleeder valve and install a pressure

gauge to one of the rear brake cylinders.

2.  Install another bleeder valve and install another

pressure gauge to the diagonally opposite front
brake.

3.  Build pressure by pressing firmly on the brake ped-

al several times. (The pressure indicated on the
gauge is not regulated and represents the actual
brake system hydraulic pressure.)

4.  Build pressure until the test values in the following

proportioning valve test chart are achieved.

Engine

Reference Number for

Gradient and Switching

Pressure on the Valve

Housing

Input Pressure Read on

the Manometer at the

Front Axle in kPa (psi)

Output Pressure Read

on the Manometer at the

Front Axle in kPa (psi)

2.0L

0.3/40

500 (73)

500 (73)

5 500 (798)

4 450 

±

 200 (645 

±

 29)

10 000 (1,450)

5 800 

±

 300 (841 

±

 44)

4B – 2

I

MASTER CYLINDER

DAEWOO V–121 BL4

Important : If the pressure exceeds 10 000 kPa (1,450
psi), the pressure reading on the rear gauge will not be ac-
curate.

5.

Remove the gauges from the tested brake circuit
and repeat the test on the remaining circuit.

MASTER CYLINDER  4B – 3

DAEWOO V–121 BL4

MAINTENANCE AND REPAIR

ON–VEHICLE SERVICE

MASTER CYLINDER ASSEMBLY

Removal Procedure

1.  Disconnect the electrical connector from the reser-

voir cap.

2.  For vehicles with the ABS braking system, discon-

nect the brake lines from the master cylinder body.

3.  For vehicles with the non–ABS braking system, dis-

connect the brake lines from the proportioning
valves.

4.  For vehicles with the manual transaxle, disconnect

the clip to the clutch hose connection to the master
cylinder and move the clip out of the way.

5.  Remove the clutch hose from the master cylinder if

equipped.

6.  Plug the opening to the brake lines to prevent fluid

loss and contamination.

7.  Remove the attaching nuts from the power booster.
8.  Remove the master cylinder assembly.
9.  Drain the brake fluid.