2001 INFINITI QX4 service

SBR451D
Checking Brake Fluid LevelNBBR0006ICheck fluid level in reservoir tank. It should be between Max
and Min lines on reservoir tank.
IIf fluid level is extremely low, check brake system.
IIf the brake warning lamp comes on, check brake fluid level
switch and parking brake switch.
SBR389C
Checking Brake LineNBBR0007CAUTION:
If leakage occurs around joints, retighten or, if necessary,
replace damaged parts.
1. Check brake lines (tubes and hoses) for cracks, deterioration
or other damage. Replace any damaged parts.
2. Check for oil leakage by fully depressing brake pedal while
engine is running.
SBR419C
Changing Brake FluidNBBR0008CAUTION:
IRefill with new brake fluid ªDOT 3º.
IAlways keep fluid level higher than minimum line on res-
ervoir tank.
INever reuse drained brake fluid.
IBe careful not to splash brake fluid on painted areas; it
may cause paint damage. If brake fluid is splashed on
painted areas, wash it away with water immediately.
1. Clean inside of reservoir tank, and refill with new brake fluid.
2. Connect a vinyl tube to each air bleeder valve.
3. Drain brake fluid from each air bleeder valve by depressing
brake pedal.
4. Refill until brake fluid comes out of each air bleeder valve.
Use same procedure as in bleeding hydraulic system to refill
brake fluid.
Refer to ªBleeding Brake Systemº, BR-8.
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ON-VEHICLE SERVICE
Checking Brake Fluid Level
BR-7

SBR995
Bleeding Brake System=NBBR0009CAUTION:
ICarefully monitor brake fluid level at master cylinder dur-
ing bleeding operation.
IIf master cylinder is suspected to have air inside, bleed air
from master cylinder first. Refer to ªInstallationº, ªMAS-
TER CYLINDERº, BR-18.
IFill reservoir with new brake fluid ªDOT 3º. Make sure it is
full at all times while bleeding air out of system.
IPlace a container under master cylinder to avoid spillage
of brake fluid.
ITurn ignition switch OFF and disconnect ABS actuator
and electric unit connectors or battery ground cable.
IBleed air in the following order.
1. LSV air bleeder (4WD)
2. Left rear brake
3. Right rear brake
4. Left front brake
5. Right front brake
SBR419C
1. Connect a transparent vinyl tube to air bleeder valve.
2. Fully depress brake pedal several times.
3. With brake pedal depressed, open air bleeder valve to release
air.
4. Close air bleeder valve.
5. Release brake pedal slowly.
6. Repeat steps 2. through 5. until clear brake fluid comes out of
air bleeder valve.
7. Tighten air bleeder valve.
:7-9N´m(0.7 - 0.9 kg-m, 61 - 78 in-lb)
ON-VEHICLE SERVICE
Bleeding Brake System
BR-8

SBR002A
SBR365AA
On-vehicle ServiceNBBR0024OPERATING CHECKNBBR0024S011. Depress brake pedal several times with engine off. After
exhausting vacuum, make sure there is no change in pedal
stroke.
2. Depress brake pedal, then start engine. If pedal goes down
slightly, operation is normal.
AIRTIGHT CHECKNBBR0024S021. Start engine, and stop it after one or two minutes. Depress
brake pedal several times slowly. Booster is airtight if pedal
stroke is less each time.
2. Depress brake pedal while engine is running, and stop engine
with pedal depressed. The pedal stroke should not change
after holding pedal down for30 seconds.
SBR368DA
RemovalNBBR0025CAUTION:
IBe careful not to splash brake fluid on painted areas; it
may cause paint damage. If brake fluid is splashed on
painted areas, wash it away with water immediately.
IBe careful not to deform or bend brake pipes, during
removal of booster.
SBR208E
InspectionNBBR0026OUTPUT ROD LENGTH CHECKNBBR0026S011. Apply vacuum of þ66.7 kPa (þ500 mmHg, þ19.69 inHg) to
brake booster with a hand vacuum pump.
2. Add preload of 19.6 N (2.0 kg, 4.4 lb) to output rod.
3. Check output rod length.
Specified length:
10.275 - 10.525 mm (0.4045 - 0.4144 in)
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BRAKE BOOSTER
On-vehicle Service
BR-19

This component controls the hydraulic circuit and increases, holds
or decreases hydraulic pressure to all or individual wheels. The
ABS actuator and electric unit is serviced as an assembly.
ABS Actuator OperationNBBR0091S0301
Inlet solenoid
valveOutlet solenoid
valve
Normal brake operation OFF (Open) OFF (Closed)Master cylinder brake fluid pressure is directly
transmitted to caliper via the inlet solenoid valve.
ABS operationPressure hold ON (Closed) OFF (Closed)Hydraulic circuit is shut off to hold the caliper
brake fluid pressure.
Pressure
decreaseON (Closed) ON (Open)Caliper brake fluid is sent to reservoir via the out-
let solenoid valve. Then it is pushed up to the
master cylinder by pump.
Pressure increase OFF (Open) OFF (Closed)Master cylinder brake fluid pressure is transmitted
to caliper.
G SENSOR (4WD MODELS ONLY)NBBR0091S05The G sensor senses deceleration during braking to determine
whether the vehicle is being driven on a high  road (asphalt road,
etc.) or a low  road (snow-covered road, etc.). It then sends a
signal to the ABS control unit.
SBR456E
The reed switch turns on when it is affected by a magnetic field.
During sudden deceleration (braking on a high  road), the weight
moves and the magnet in the weight moves away from the reed
switch. The magnetic field then diminishes and the reed switch
turns off.
DESCRIPTIONABS
System Description (Cont'd)
BR-34

SEF233G
SEF234G
How to Perform Trouble Diagnoses for Quick
and Accurate Repair
NBBR0098INTRODUCTIONNBBR0098S01The ABS system has an electronic control unit to control major
functions. The control unit accepts input signals from sensors and
instantly drives the actuators. It is essential that both kinds of sig-
nals are proper and stable. It is also important to check for conven-
tional problems: such as air leaks in booster lines, lack of brake
fluid, or other problems with the brake system.
It is much more difficult to diagnose a problem that occurs intermit-
tently rather than continuously. Most intermittent problems are
caused by poor electric connections or faulty wiring. In this case,
careful checking of suspicious circuits may help prevent the
replacement of good parts.
A visual check only may not find the cause of the problems, so a
road test should be performed.
Before undertaking actual checks, take a few minutes to talk with
a customer who approaches with an ABS complaint. The customer
is a very good source of information on such problems; especially
intermittent ones. By talking to the customer, find out what symp-
toms are present and under what conditions they occur. Start your
diagnosis by looking for ªconventionalº problems first. This is one
of the best ways to troubleshoot brake problems on an ABS con-
trolled vehicle.
Also check related Service bulletins for information.
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TROUBLE DIAGNOSIS Ð INTRODUCTIONABS
How to Perform Trouble Diagnoses for Quick and Accurate Repair
BR-49

4 CHECK BRAKE BOOSTER OPERATION
Check brake booster for operation and air tightness.
Refer to ªOn-vehicle Serviceº, ªBRAKE BOOSTERº, BR-19.
SBR058C
Is brake booster airtight and functioning properly?
Ye s©GO TO 5.
No©Replace. GO TO 5.
5 CHECK BRAKE PAD AND ROTOR
Check brake pad and rotor.
Refer to (BR-22, BR-24).
SBR059C
Are brake pads and rotors functioning properly?
Ye s©GO TO 6.
No©Replace.
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TROUBLE DIAGNOSIS Ð BASIC INSPECTIONABS
Preliminary Check (Cont'd)
BR-51

General SpecificationsNBBR0118Unit: mm (in)
Applied model2WD 4WD
Front brakeBrake model AD31VC
Cylinder bore diameter´number of pistons 44.45 (1.7500)´2
Pad
Length´width´thickness132.0´52.5´11
(5.20´2.067´0.43)
Rotor outer diameter´thickness 300´28 (11.81´1.10)
Rear brakeBrake model LT30C
Cylinder bore diameter 22.23 (7/8)
Lining length´width´thickness296´50´6.1
(11.65´1.97´0.240)
Drum inner diameter 295.0 (11.61)
Master cylinder Bore diameter 25.40 (1)
Control valveValve modelProportioning valve
within master cylinderLinkage type load
sensing valve
Split point
kPa (kg/cm
2, psi)´reducing ratio2,942 (30, 427)´0.2 (Variable)´0.18
Brake boosterBooster model M235T
Diaphragm diameterPri: 252 (9.92)
Sec: 205 (8.07)
Recommended brake fluidDOT 3
Disc BrakeNBBR0119Unit: mm (in)
Brake modelAD31VC
Pad wear limit Minimum thickness 2.0 (0.079)
Rotor repair limit Minimum thickness 26.0 (1.024)
Drum BrakeNBBR0120Unit: mm (in)
Brake modelLT30C
Lining wear limit Minimum thickness 1.5 (0.059)
Drum repair limitMaximum inner diameter 296.5 (11.67)
Out-of-round limit 0.03 (0.0012)
Brake PedalNBBR0121Unit: mm (in)
TransmissionA/T
Free height ªHº*175 - 185
(6.89 - 7.28)
Depressed height ªDº*
[under force of 490 N (50 kg, 110 lb) with engine running]70 (2.76)
Clearance ªCº between pedal stopper and threaded end of stop lamp switch or ASCD switch 0.3 - 1.0 (0.012 - 0.039)
Pedal free playAt clevis 1.0 - 3.0 (0.039 - 0.118)
At pedal pad1 - 3 (0.04 - 0.12)
*: Measured from surface of metal panel to pedal pad
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SERVICE DATA AND SPECIFICATIONS (SDS)
General Specifications
BR-83

Parking Brake ControlNBBR0084Unit: notch
Control TypeCenter lever
Lever stroke
[under force of 196 N (20 kg, 44 lb)]6-8
Lever stroke when warning switch comes on 1 or less
SERVICE DATA AND SPECIFICATIONS (SDS)
Parking Brake Control
BR-84