ACURA NSX 1991 Service Repair Manual

Rear Calipe r
Disassembl y (cont'd )
12. Remov e th e adjustin g bolt .
13. Remov e th e sprin g cover , adjustin g sprin g B ,
spacer , bearin g A an d cu p fro m th e adjustin g bolt .
14. Remov e th e sleev e piston , an d remov e th e pi n fro m
the cam .
1 5 . Remov e th e retur n spring .
16. Remov e th e parkin g leve r an d ca m a s a n assembl y
from th e calipe r body .
CAUTION : D o no t loose n th e parkin g nu t wit h th e
ca m installe d i n th e calipe r body . I f th e leve r an d
shaf t mus t b e separated , hol d th e leve r i n a vis e
an d loose n th e parkin g nut .
17. Remov e th e ca m boot .
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Reassembly
CAUTION:
• Mak e sur e al l part s ar e clea n befor e reassembly .
• Us e onl y ne w replacemen t parts .
• Us e onl y clea n DOT 3 o r 4 brak e fluid .
• D o no t allo w dir t o r othe r foreig n matte r t o con -
taminat e th e brak e fluid .
• Avoi d spillin g brak e flui d o n painted , plasti c o r rubbe r
surface s a s i t ca n damag e th e finish . Was h spille d
brak e flui d of f immediatel y wit h clea n water .
1 . Pac k al l cavitie s o f th e needl e bearin g wit h a com -
mercially-availabl e assembl y lube .
2. Coa t th e ne w ca m boo t wit h a commercially -
available assembl y lub e an d instal l i n th e caliper .
3 . Appl y commercially-availabl e assembl y lub e t o th e
pi n contactin g are a o f th e cam , an d instal l th e ca m
an d leve r assembl y int o th e calipe r body .
4. Instal l th e retur n spring .
CAUTION :
• Whe n th e ca m an d leve r wer e separated , b e
sur e t o assembl e the m befor e installin g th e ca m
i n th e calipe r body . Instal l th e leve r an d sprin g
washer , appl y lockin g agen t t o th e threads , an d
tighte n th e parkin g nu t whil e holdin g th e leve r
wit h a vise .
• Avoi d damagin g th e ca m boo t sinc e i t mus t b e
installe d befor e th e cam .
• Whe n installin g th e cam , d o no t allo w th e ca m
boo t lip s t o tur n outsid e in .
5. Instal l th e pi n in th e cam .
6. Instal l a ne w O-rin g o n th e sleev e piston .
7. Instal l th e sleev e pisto n s o th e hol e in th e botto m of
the pisto n is aligne d wit h th e pi n in th e cam , an d
the tw o pin s o n th e pisto n ar e aligne d wit h th e hole s
in th e caliper .
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15. Instal l th e adjustin g nut , adjustin g sprin g A , an d
washer , the n secur e wit h th e circlip .
07HAE-SG0010 0
07HEA-SG0010 0
Rear Calipe r
Reassembl y (cont'd )
8. Instal l a ne w cu p wit h it s groov e facin g th e bearin g
A sid e o n th e adjustin g bolt .
9. Fi t th e bearin g A , spacer , adjustin g sprin g B an d
sprin g cove r o n th e adjustin g bolt , an d instal l i n th e
calipe r cylinder .
NOTE : Instal l th e bearin g A wit h it s ope n en d fac -
in g th e spacer .
10 . Adjus t th e specia l too l a s shown .
11. Instal l th e specia l too l a s shown .
12. Compres s th e sprin g unti l i t bottom s out .
13. Chec k tha t th e flare d en d o f th e sprin g cove r i s
belo w th e circli p groove .
14 . Instal l th e circlip , the n remov e th e brak e sprin g
compressor .
NOTE : Chec k tha t th e circli p i s seate d i n th e
groov e properly .
SNAP RIN G PLIER S07914-SA5000 0
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16. Coa t th e ne w pisto n sea l an d pisto n boo t wit h
silicon e grease , an d instal l the m in th e caliper .
17 . Coa t th e outsid e of the pisto n wit h silicon e grease ,
and instal l i t o n th e adjustin g bol t whil e rotatin g i t
clockwise .
CAUTION : Avoi d damagin g th e pisto n an d pisto n
boot.
18. Instal l th e brak e pa d retainer s an d brak e pads .
19 . Instal l th e pa d sprin g o n th e caliper .
20 . Instal l th e calipe r o n th e calipe r bracket , an d tighte n
the calipe r mountin g bolts .
21. Connec t th e brak e hos e t o th e calipe r wit h ne w
sealin g washers , an d tighte n th e banj o bolt .
22. Connec t th e parkin g brak e cabl e t o th e ar m o n th e
caliper .
23 . Fil l th e brak e reservoi r up , an d blee d th e brak e
syste m (se e pag e 19-10 ).
24 . Operat e th e brak e peda l severa l times , the n adjus t
th e parkin g brak e lever .
NOTE : Befor e adjustments , mak e sur e th e parkin g
brak e ar m o n th e calipe r touche s th e pin .
25. Instal l th e calipe r shiel d an d tighte n th e bolts .
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Brake Hoses/Pipe s
Inspection
1. Inspec t th e brak e hose s fo r damage , deterioration , leaks , interferenc e o r twisting .
2 . Chec k th e brak e line s fo r damage , rustin g an d leakage . Als o chec k fo r ben t brak e lines .
3 . Chec k fo r leak s a t hos e an d lin e joint s o r connections , an d retighte n i f necessary .
CAUTION : Replac e th e brak e hos e cli p wheneve r th e brak e hos e i s serviced .
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Parking Brak e
Disassembl y an d Reassembl y
CAUTION: Th e parkin g brak e cable s mus t no t b e ben t o r distorted . Thi s wil l lea d t o stif f operatio n an d permatur e cabl e
failure .
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Anti-lock Brake System (ABS) Description

Features/Construction/Operation

General

In a conventional brake system, if the brake pedal is depressed excessively, the wheels can lock before the vehicle

comes to a stop. In such a case, the stability of the vehicle is reduced if the rear wheels are locked, and maneuverabily of

the vehicle is reduced if the front wheels are locked, creating an extremely unstable condition.

The Anti-lock Brake System (ABS) modulates the pressure of the brake fluid applied to each caliper, thereby preventing

the locking of the wheels, whenever the wheels are likely to be locked due to excessive braking. It then restores normal

hydraulic pressure when there is no longer any possibility of wheel locking.

4-Channel Anti-lock Brake System (ABS) Features

• Increased braking stability can be achieved regardless of changing driving conditions.

• The maneuverability of the vehicle is improved as the system prevents the front wheels from locking.

• When the anti-lock brake system goes into action, kickback is felt on the brake pedal.

• The anti-lock brake system is equipped with a self-diagnosis function. When an abnormality is detected, the ABS in-

dicator light comes on. The location of the abnormality can be diagnosed from the frequency of the system indicator

light display blinks.

• This system has individual control of the front and rear wheels. Braking force is controlled on each of the four wheels

independently, resulting in optimum braking effects on the four wheels.

The system has a fail-safe function that allows normal braking if there's a problem with the anti-lock brake system.

Construction

In addition to the conventional braking system, the anti-lock brake system is composed of: gear pulsers attached to the

rotating part of individual wheels; wheel sensors, which generate pulse signals in correspondence to the revolution of the

gear pulsers; ABS control unit, which controls the working of the anti-lock brake system by performing calculations bas-

ed on the signals from the individual wheel sensors and the individual switches; a modulator unit, which adjusts the

hydraulic pressure applied to each caliper on the basis of the signals received from the ABS control unit; an accumulator,

in which high-pressure brake fluid is stored; a pressure switch, which detects the pressure in the accumulator and

transmits signals to the ABS control unit; a power unit, which supplies the high-pressure working fluid to the ac-

cumulator by means of a pump; a motor relay for driving the power unit; a fail-safe relay, which cuts off the solenoid

valve ground circuit when the fail-safe device is at work; and, an ABS indicator light.ProCarManuals.com

Master Cylinder

1. Construction

A tandem master cylinder with center valves are used to improve braking system safety.

The master cylinder has one reservoir tank which is connected to the cylinder sections by two small holes. It has two

pistons - primary and secondary, which are crisscross connected with the calipers so that the fluid pressure works

separately on each system (front right wheel & rear left wheel, and front left wheel & rear right wheel).

A stop bolt for controlling movement of the primary piston is provided at the side of the master cylinder body.

A reed switch for detecting the brake fluid volume is also provided on the cap of the reservoir tank.

2. Operation

When the brake pedal is depressed, the secondary piston is pushed through the brake booster and center valve B is

closed so that the fluid pressure is generated on the secondary side. At the same time, the primary piston is pushed

by the secondary fluid pressure and center valve A is closed so that braking fluid pressure is generated both on the

primary and secondary sides.

When the brake pedal is released, the primary and secondary pistons are returned to the original positions by the

brake fluid pressure and piston spring.ProCarManuals.com

Anti-lock Brake System (ABS) Description

Features/Construction/Operation (cont'd)

3. Responses when fluid is leaking

(1) In case of leaking from the primary system

Since the fluid pressure on the primary side does not rise, the primary piston is pushed by the fluid pressure of

the secondary piston and the tension of the piston spring until the end hits on the cylinder; the braking is per-

formed by the fluid pressure on the secondary side.

(2) In case of leaking from the secondary system

The secondary piston does not produce fluid pressure, keeps moving ahead, hits on the end surface of the

primary piston so that the primary piston is pushed under the same condition as an ordinary rod; the braking is

performed by the fluid pressure on the primary side.ProCarManuals.com

Wheel Sensor

The wheel sensor is a contactless type, and it detects the rotating speeds of a wheel. It is composed of a permanent

magnet and coil. When the gear pulsers attached to the rotating parts of each wheel (rear wheel: outboard joint of the

driveshaft, front: hub bearing unit) turn, the magnetic flux around the coil in the wheel sensor alternates, generating

voltages with frequency in proportion to wheel rotating speed. These pulses are inputted into the ABS control unit, and

the ABS control unit identifies the wheel speeds.ProCarManuals.com