Daewoo Nubira. Manual - part 55

4B – 8

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MASTER CYLINDER

DAEWOO V–121 BL4

UNIT REPAIR

MASTER CYLINDER OVERHAUL

Disassembly Procedure

1.  Remove the master cylinder. Refer to”Master Cylin-

der Assembly”in this section.

2.  Remove the brake fluid reservoir. Refer to”Brake

Fluid Reservoir”in this section.

3.  Remove the seal ring from the cylinder bore.

Notice : When removing the retaining ring, avoid damag-
ing the piston or the cylinder wall.

Important : A welding rod or its equivalent can be used in
a compensating port to keep the piston depressed.

4.  Remove and discard the retaining ring from the cyl-

inder body (the non–ABS master cylinder body is
shown) using a suitable screwdriver.

5.   Remove the primary piston (the ABS master cylin-

der body is shown).

6.  Carefully remove the secondary piston assembly,

including the springs, from the master cylinder
bore.

MASTER CYLINDER  4B – 9

DAEWOO V–121 BL4

Assembly Procedure

Notice : Do not use abrasives in the master cylinder bore.
Abrasives can damage the bore.

Important : Rubber parts and retaining rings must be dis-
carded and replaced with new parts.

1.  Clean all parts with denatured alcohol or clean

brake fluid. Dry the parts with compressed air. Do
not use lubricated shop air on brake parts, as this
may damage rubber components.

2.  Inspect the master cylinder bore for scoring or cor-

rosion. If scoring or corrosion is evident, replace the
master cylinder body.

3.  Lubricate the master cylinder bore (the non–ABS

master cylinder is shown) with clean brake fluid.

4.  Carefully insert the secondary piston assembly bore

until the secondary piston contacts the base of the
cylinder body. Use a wood or a plastic drift, if nec-
essary.

5.  Insert the primary piston.

6.  Press the pistons into the cylinder bore using a

wooden or a plastic drift.

Notice : When installing the new retaining ring, take care
not to damage the cylinder bore.

7.  Insert the new retaining ring into the groove in the

cylinder bore (the non–ABS cylinder body is
shown). Remove the welding rod.

8.  Move the pistons backward and forward after instal-

lation to check for free movement.

4B – 10

I

MASTER CYLINDER

DAEWOO V–121 BL4

9.  Lubricate the seal ring and insert the seal into the

cylinder bore. The open side must face outward
until the seal rests on the piston.

10.  Install the brake fluid reservoir to the master cylin-

der. Refer to”Brake Fluid Reservoir”in this section.

11.  Install the master cylinder assembly. Refer to

the”Master Cylinder Assembly”in this section.

12.  Raise and suitably support the vehicle.
13.  Bleed the braking system. Refer toSection 4A, Hy-

draulic Brakes or Section 4F, Antilock Brake Sys-
tem.

14.  Lower the vehicle.

MASTER CYLINDER  4B – 11

DAEWOO V–121 BL4

GENERAL DESCRIPTION

AND SYSTEM OPERATION

MASTER CYLINDER

The master cylinder is designed for use in a diagonalsplit
system. One front and one diagonally opposite rear brake
are served by the primary piston. The opposite front and
rear brakes are served by the secondary piston. The mas-
ter cylinder incorporates the functions of the standard dual
master cylinder, plus a low fluid level indicator and the pro-
portioning valves in the non–antilock braking system. The
proportioning valves limit the outlet pressure to the rear
brakes after a predetermined master cylinder pressure
has been reached.

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Replace all the components included in the repair
kits used to service this master cylinder.

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Lubricate rubber parts with clean brake fluid to ease
assembly.

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Do not use lubricated shop air on brake parts, as
this may damage rubber components.

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If any hydraulic component is removed or discon-
nected, it may be necessary to bleed all or part of
the brake system.

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The torque values specified are for dry, unlubri-
cated fasteners.

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Perform all service operations on a clean bench,
free from all traces of mineral oil.

PROPORTIONING VALVE

The proportioning valves limit the outlet pressure to the
rear brakes on the non–antilock braking system after a
predetermined master cylinder pressure has been
reached. This is used when less rear apply force is needed
to obtain optimum braking and is usually found on disc/
drum brake configurations. On ABS–equipped vehicles,
refer toSection 4F, Antilock Brake System.

FLUID LEVEL SENSOR

The master cylinder is equipped with a fluid level sensor.
This sensor will activate the BRAKE light if a low fluid level
condition is detected. Once the fluid level is corrected, the
BRAKE light will go out.