1995 ACURA TL lock

10. Instal l th e specia l too l o n th e sprin g cover , an d tur n
the shaf t unti l th e locknu t contact s th e plate .
SHAF T
LOCKNUT S
BRAKE SPRIN GCOMPRESSO R07HAE-SG0010 0 SPRIN
G
COVER
CIRCLI PGROOV E
11. 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 .
12 . Instal l th e circli p i n th e groove , the n remov e th e
specia l tool .
NOTE : Chec k tha t th e circli p is seated in th e groov e
properly .
13. Coa t a ne w pisto n sea l wit h recommende d silicon e
grease in th e calipe r sea l set , an d instal l i t i n th e cali -
per. PISTO N SEA LReplace .
RUBBERGREAS E
14. Appl y recommende d rubbe r greas e i n th e calipe r
sea l se t t o th e sealin g lip s an d insid e o f a ne w pis -
to n boot , an d instal l i t i n th e caliper .
15 . Coa t th e outsid e o f th e pisto n wit h brak e fluid , an d
instal l i t o n th e adjustin g bol t whil e rotatin g i t clock -
wis e wit h th e tool .
CAUTION : Avoi d damagin g th e pisto n an d pisto n
boot.
PISTO N
LOCKNU T WRENC H
(Commerciall y
available)
16. Instal l th e pa d sprin g o n th e calipe r
PAD SPRIN G
PLATE
SILICON EGREASE
PISTON BOO TReplace .
CIRCLIP
SPRING GUID E
SNA
P RIN G
PLIER S07914-SA5000 0
ProCarManuals.com

Parking Brake Cable

Inspection and Replacement

CAUTION: The parking brake cables must not be bent or distorted. This will lead to stiff operation and premature cable

failure.

CLEVIS PIN

CLIP

Replace.

BRACKET

PARKING BRAKE CABLE

Check for faulty movement.

PARKING BRAKE LEVER

Check for smooth

operation.

PARKING BRAKE SWITCH

(Sliding surface)

Disconnect the parking brake cable from the lever on the

caliper by removing the lock pin and clevis pin, and

remove the cable from the arm by removing the clip.

PARKING BRAKE CABLE

CLIP

Replace.
LEVER

CLEVIS PIN
LOCK PIN

Replace.

LOCK PIN
LOCK PIN

Replace.

ADJUSTING

NUT

EQUALIZERProCarManuals.com

Anti-lock Brake System (ABS)

Features/Construction

In a conventional brake system, if the brake pedal is depressed very hard, 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 maneuverability of the vehi-

cle 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 front caliper or both rear

calipers, thereby preventing the locking of the wheels, whenever the wheels are likely to be locked due to hard braking. It

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

The ABS equipped on this car is compact, with its hydraulic control system incorporated into one modulator unit. It is a

3-channel anti-lock brake system that has individual control of the front wheels and common control ("select low") for the

rear wheels. "Select low" means that the rear wheel that would lock first (the one with the lowest resistance to lock-up)

determines anti-lock brake system activation for both rear wheels.

ABS CONTROL UNIT

GEAR PULSER

MASTER CYLINDER

MODULATOR UNIT

REAR WHEEL SENSOR

GEAR PULSER
FRONT WHEEL SENSOR

PART NAME

Gear pulser

Wheel sensor

ABS control unit

Modulator unit

Motor Relay

Fail-safe relay
MAJOR FUNCTION

Attached to the rotating part of the wheel and detects the wheel speed together with the

wheel sensor.

Generates pulse signal corresponding to the revolution of the gear pulser.

Controls the working of the anti-lock brake system by performing calculations based on the

signals from the individual wheel sensors and the individual switches.

• Adjusts the hydraulic pressure applied to each caliper on the basis of the signals received

from the ABS control unit.

• Pump, accumulator, solenoid valves, pressure switch and pistons are integrated in the mod-

ulator unit.

Controls the ABS pump motor's power supply according to the signal from the ABS control unit.

Cuts off the solenoid valve ground circuit when the fail-safe device is at work.ProCarManuals.com

Anti-lock Brake System (ABS)

Features/Construction (cont'd)

Accumulator:

The high-pressure brake fluid discharged from the pump

is fed to the solenoids and pistons, but the passages to

the solenoids and pistons are normally closed. Con-

sequently, the high-pressure brake fluid accumulates in

the accumulator.

The accumulator consists of two chambers separated by

a free piston; that is, the fluid chamber where the brake

fluid is accumulated, and the chamber filled with high-

pressure nitrogen gas to maintain the fluid at a given

pressure.

When the ABS operates, the constant high-pressure

brake fluid in the accumulator is supplied to the piston.
GAS CHAMBER

(FILLED WITH NITROGEN GAS)

FLUID CHAMBER O-RINGS

FREE PISTON
RELIEF PLUG

Pressure switch:

The pressure switch monitors the pressure accumula-

tion in the accumulator. When the pressure in the accu-

mulator rises, the Bourdon tube in the pressure switch

deforms outward, which in turn activates the micro-

switch by the force of the spring attached to the sensing

lever. When the pressure in the accumulator drops due

to ABS operation, the Bourdon tube moves in the oppo-

site direction, and the micro-switch is eventually turned

off.

The ABS control unit detects the fluid pressure in the

accumulator by the ON/OFF signals from the pressure

switch.
MICRO-SWITCH

SENSING LEVER

BOURDON TUBEProCarManuals.com

Piston/valve:

The piston/valve assembly consists of the piston, cut valve, and sleeve. There are four piston/valve assemblies in the mod-

ulator unit to control the brake fluid pressure to each caliper. The piston/valve assemblies for the rear brakes also serve as

proportioning control valves to prevent the rear wheels from locking if the ABS malfunctions or when the ABS is not acti-

vated.

Solenoid valves:

The modulator unit opens and closes the inlet and outlet solenoid valves, and shifts the ABS high-pressure passage

according to the signals from the ABS control unit. There are three solenoid valve assemblies, each containing an inlet

and outlet valve, in the modulator unit; one for each front wheel, and one for both rear wheels. The inlet valves are nor-

mally open (open when the coil is not energized), while the outlet valves are normally closed.

MODULATOR UNIT

RESERVOIR

To ABS CONTROL

UNIT

To RIGHT-FRONT

WHEEL

To LEFT-FRONT

WHEEL

PUMP MOTOR RELAY
From MASTER

CYLINDER

PRIMARY PISTON

From MASTER

CYLINDER

SECONDARY

PISTON

To LEFT-REAR

WHEEL

To RIGHT-

REAR WHEEL
MOTOR
PUMP

PISTON/VALVE
CUT

VALVE
PISTON
SLEEVE
SOLENOID VALVES (3 SETS)

RELIEF

VALVE

ACCUMULATOR

PRESSURE

SWITCHProCarManuals.com

Anti-lock Brake System (ABS)

Features/Construction (cont'd)

Wheel sensor:

The wheel sensor is a contactless type that detects the rotating speed of a wheel. It consists of a permanent magnet and

coil. When the gear pulsers attached to the rotating parts of each wheel 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 sent

to the ABS control unit, and the ABS control unit identifies the wheel speed.

WHEEL SENSOR

COIL PERMANENT MAGNET

at HIGH SPEED

at LOW SPEED

GEAR PULSER

GEAR PULSER

ABS control unit:

The ABS control unit consists of a main function, which controls the operation of the anti-lock brake system, and sub-func-

tion, which controls the pump motor and "self-diagnosis".

For safety, the main function consists of two systems, and the ABS control unit activates the solenoid valve only when the

outputs of the two systems agree with each other.

The main function section of the ABS control unit performs calculations on the basis of the signals from each wheel

sensor, and controls the operation of the anti-lock brake system by activating the solenoid valves in the modulator unit

for each front brake and for the two rear brakes. The ABS has individual control of the front wheels and common con-

trol ("Select low") for the rear wheels. "Select low" means that the rear wheel that would lock first (the one with the

lowest resistance to lock-up) determines the ABS activation for both rear wheels.

The sub-function section has the fail-safe function that monitors the system operation by inputting the brake switch,

parking brake switch and pressure switch signals, and stops the anti-lock brake system when it detects an abnormality

in the system. It also has a self-diagnosis function and the pump motor control function.

WHEEL SENSORS
ABS CONTROL UNIT

RIGHT-FRONT WHEEL

LEFT-FRONT WHEEL

RIGHT-REAR WHEEL

LEFT-REAR WHEEL

BRAKE SWITCH

PARKING BRAKE SWITCH
MAIN FUNCTION

• BASIC ABS

FUNCTION CONTROL

SUB-FUNCTION

• SELF-DIAGNOSIS FUNCTION

• FAIL-SAFE FUNCTION

• PUMP MOTOR CONTROL

PRESSURE SWITCH

PUMP MOTOR RELAY
MODULATOR UNIT

SOLENOID

SOLENOID

SOLENOID

FRONT FAIL - SAFE RELAY

REAR FAIL - SAFE RELAY

PUMP MOTORProCarManuals.com

Anti-lock Brake System (ABS)

Operation

The following description of ABS operation is for one of

the front wheels. The ABS operation for the remaining

wheels is the same.

Ordinary braking function:

In ordinary brake operations when the ABS is not func-

tioning, the solenoid outlet valve is closed and the inlet

valve is open, the brake fluid pressure is transmitted to

the back-pressure chamber between the sleeve and pis-

ton, and the cut valve is pushed by the piston. As the

high-pressure is also transmitted to chamber A between

the sleeve and cylinder, the sleeve pushes the cut valve

seat toward the cut valve, too.

Under there conditions, the cut valve is kept open, and

the hydraulic pressure from the master cylinder is trans-

mitted to the caliper just like an ordinary brake system.
BACK-PRESSURE CHAMBER

MASTER CYLINDER

CUT VALVE (OPEN)

CUT VALVE SEAT

PISTON

SOLENOID VALVE

PUMP

ACCUMULATOR PRESSURE SWITCH

When ABS is functioning:

Control by reducing caliper fluid pressure:

When brake inputs (force exerted on brake pedal) are

excessively large, and a possibility of wheel locking

occurs, the control unit operates the solenoid valve,

closing the inlet valve and opening the outlet valve.

As a result, high pressure in the back-pressure cham-

ber is released to the reservoir, and the piston is

pushed by the caliper fluid pressure toward the back-

pressure chamber. However, the cut valve seat is

kept in the pushed position because high pressure is

transmitted to chamber A. As the piston moves, the

cut valve moves and shuts the flow from the master

cylinder to the caliper, the volume of the pressure

reduction chamber connected to the caliper increas-

es, and the fluid pressure in the caliper declines,

relieving the braking force. The wheel speed is there-

fore restored, preventing the wheel from locking.
RESERVOIR

PRESSURE REDUCTION CHAMBER
CALIPER

CHAMBER A

SLEEVE

PRESSURE DECLINES.

CHAMBER A

CUT VALVE (CLOSE)ProCarManuals.com

Control by increasing caliper fluid pressure:

When the ABS control unit senses that the caliper fluid

pressure declined, and the wheel speed is restored, it

signals the solenoid inlet valve to open and the

solenoid outlet valve to close.

As a result, the high-pressure brake fluid is transmitted

to the back-pressure chamber, and the piston is pushed

toward the pressure reduction chamber, increasing

the caliper fluid pressure, and thereby the braking

force again.

When the master cylinder side's fluid pressure is low,

the cut valve is slightly opened as the piston moves,

and the caliper fluid pressure is transmitted to the

master cylinder. The kickback is felt on the brake

pedal this time. When the force depressing the brake

pedal is relieved while the ABS is functioning, the cut

valve is opened and the pressure in the pressure

reduction chamber is returned to the master cylinder

side. As a result, the caliper fluid pressure is relieved.
MASTER CYLINDER

PRESSURE INCREASES

CUT VALVE

PRESSURE REDUCTION CHAMBER

SOLENOID VALVES

When high-pressure declines:

The ABS control unit monitors the pressure in the high-

pressure passage by means of the pressure switch sig-

nals. The ABS control unit turns the ABS indicator light

on, and stops the ABS when it detects an excessive drop

in pressure in the high-pressure passage.

When the pressure declined due to leakage from the pas-

sage, for example, the pressure in chamber A declines,

too, and the cut valve seat and sleeve return toward

chamber A.

As a result, the valve at the sleeve end closes, which

hydraulically locks the back-pressure chamber and

blocks the piston movement. Because the cut valve

opens as the cut valve seat moves, this connects the

brake fluid passage between the master cylinder and

caliper for ordinary brake operation.ProCarManuals.com