Brake Drums; Wheel Cylinder Repair - Chevrolet CHEVY VAN G10 SERIES Service Manual

BRAKES 5-14

Wheel Cylinder Repair

Wheel cylinders should not be disassembled unless they are
leaking or unless new cups and boots are to be installed. I t is
n o t necessary to remove the brake cylinder from the backing
plate to disassemble, inspect, and overhaul the cylinder.
Removal is necessary only when the cylinder is damaged or
scored beyond repair.
Removal
1. Place vehicle on a hoist.
2. Remove wheel and tire assem bly. Back o ff brake adjust­
m ent, if necessary, and remove drum .
3. D isconnect brake system hydraulic line from cylinder.
4. Remove brake shoe pull back springs.
5. Remove screws securing wheel cylinder to flange plate.
Disengage cylinder push rods from brake shoes and
remove cylinder.
Disassembly (Fig. 28)
1. Remove boots from cylinder ends.
2. Remove pistons and cups.
Inspection and Cleaning
N O T E : Staining is not to be confused w ith cor­
rosion. Corrosion can be identified with pits or
excessive bore roughness.
1. Inspect cylinder bore, Check for staining and corrosion.
Discard cylinder if corroded.
2. Polish any discolored or stained area w ith crocus clo th by
revolving the cylinder on the cloth sup ported by a finger.
Do not slide the cloth in a lengthwise m anner under
pressure.
C A U T IO N : Before washing parts, hands must be
clean. Do not wash hands in gasoline or oil before
cleaning parts. Use soap and water to clean hands.
PUSH R O D A N D B O O T
CUP RETURN S PR IN G W IT H E X P A N D I
W H E E L C Y LIN D E R H O U S IN G
P IS T O N CUP
P IS TO N
PUSH R O D A N D B O O T
Fig. 2 8 —Wheel C ylinder—Explode
P IS TO N
P IS T O N CUP
BLEEDER S C REW
3. Wash the cylinder and m etal parts in denatured alcohol.
4. Remove excess cleaning fluid from the cylinder. Do n ot
use a rag to dry the cylinder as lint from the rag cannot
be k ep t from the cylinder bore surfaces.
5. Check piston for scratches or oth er visual damage; re­
place if necessary.
Assembly
1. L ubricate the cylinder bore w ith clean brake fluid and
insert spring-expander assembly.
2. Install new cups w ith flat surface tow ard outer ends of
cylinder. Be sure cups are lint and dirt free before
insertion. Do n o t lubricate cups prior to assembly.
3. Install new pistons in to cylinder w ith flat surfaces tow ard
center o f cylinder. Do not lubricate pistons before
installation.
4. Press new boots o n to cylinder by hand. Do n o t lubricate
boots prior to installation.
Installation
1. Position wheel cylinder to brake flange p late. Install
screws and tighten securely.
C A U T IO N : See "C autio n"
section.
2. Install all push rods and pull back springs.
3. C onnect hose or line to wheel cylinder.
C A U T IO N : See "C a u tio n "
section.
4. Install all parts rem oved for accessibility.
5. Bleed hydraulic system as outlined in this section.
6 . Check brake pedal operation and remove vehicle from
hoist.

BRAKE DRUMS

A lanced " k n ock o u t" area is provided in the web o f the
brake drum or backing plate for servicing purposes in the event
retracting o f the brake shoes is required in order to remove the
drum .
A small screwdriver or h o o k ed wire m ay be inserted to
disengage the autom atic adjuster actuating lever so the star
wheel may be tu rn ed (Fig. 22).
Inspection and Reconditioning
Whenever brake drum s are rem oved, they should be
thoroughly cleaned and inspected for cracks, scores, deep
grooves and out-of-round. Any o f these conditions m ust be
corrected since they can im pair the efficiency o f brake
operation and cause prem ature failure o f o th e r parts.
W A R N IN G : A cracked drum is unsafe for further
service and must be replaced. Do n o t atte m p t to
weld a cracked drum.
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