1991 LEXUS SC400 Brake Pedal

DIAGNOSTIC TROUBLE CODE
CLEARANCE
1. Using SST, connect terminals Tc and E1 of DLC2 or DLC1.SST 09843±18020
2. IG switch ON.
3. Clear the diagnostic trouble codes stored in ECU by depressing the brake pedal 8 or more times within 3 seconds.
4. Check that the TRAC indicator light shows the normal code.
5. Remove the SST from the terminals of DLC2 or DLC1.
HINT: Cancellation can also be done by removing the DOME
fuse, but in this case, other memory systems will also be can-
celled out.
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±171
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SERVICE SPECIFICATIONS
SERVICE DATA
BR03A±0G\
\
Brake pedal height from asphalt sheet (LHD)  150.4±160.4 mm (5.92±6.31 in.)
\


\
Brake pedal freeplay 




1±6 mm (0.04±0.24 in.)
\


\
Brake pedal reserve distance at 490 N (50 kgf, 110.2
lbf) 





More than 89 mm (3.50 in.)
\
\
Brake booster push rod to piston clearance (w/ SST)  0 mm (0 in.)
\
\
Front brake pad thickness STD 11.0 mm (0.433 in.)
\
\
Front brake pad thickness Limit 1.0 mm (0.039 in.)\


\
Front brake disc thickness (SC 300)
 


STD


28.0 mm (1.102 in.)
\
\
Front brake disc thickness (SC 300) Limit 26.0 mm (1.024 in.)
\
\
Front brake disc thickness (SC 400) STD 32.0 mm (1.260 in.)
\


\
Front brake disc thickness (SC 400) 


Limit

30.0 mm (1.181 in.)
\
\
Front brake disc runout Limit 0.05 mm (0.0020 in.)
\
\
Rear brake disc pad thickness STD 10.0 mm (0.394 in.)
\
\
Rear brake disc pad thickness Limit 1.0 mm (0.039 in.)\


\
Rear brake disc thickness
 


STD


16.0 mm (0.630 in.)
\
\
Rear brake disc thickness Limit 15.0 mm (0.591 in.)
\
\
Rear brake disc runout Limit 0.05 mm (0.0020 in.)
\


\
Rear brake disc inside diameter 


STD

190 mm (7.48 in.)
\
\
Rear brake disc inside diameter Limit 191 mm (7.52 in.)
\
\
Parking brake lining thickness STD 2.5 mm (0.098 in.)
\
\
Parking brake lining thickness Limit 1.0 mm (0.039 in.)\


\
Parking brake lever travel at 196 N (20 kgf, 44.1 lbf)
 




5±8 clicks
\
\
Parking brake clearance between rear shoe and lever  Less than 0.35 mm (0.012 in.)
\


\
Parking brake adjusting shim thickness for rear disc
brake 




0.3 mm (0.012 in.)
\
\
  0.6 mm (0.024 in.)
\


\
 




0.9 mm (0.035 in.)
±
BRAKE SYSTEM SERVICE SPECIFICATIONSBR±229
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TORQUE SPECIFICATIONS
BR03B±0G\
 
\

\
Part tightened
 

N
Vm
 

kgf
Vcm
 

ft
Vlbf
\
 \
Master cylinder x Piston stopper bolts 10 100 7
\
 \
Master cylinder x Reservoir 1.7 17.5 15.2 in. Vlbf
\
 
\

\
Master cylinder x Brake booster 

13 

130 

9
\
 \
Brake tube union nut 15 155 11
\
 \
Brake booster clevis lock nut 25 260 19
\
 \
Brake booster x Pedal bracket 15 150 11\
 
\

\
Bleeder plug (TRAC actuator and TRAC accumulator)
 

8.3
 

85
 

74 in.
Vlbf
\
 \
Bleeder plug 11 11 0 8
\
 \
Front disc brake torque plate x Steering knuckle 11 8 1,200 87
\
 \
Front disc brake cylinder installation bolt 34 350 25\
 
\

\
Front disc brake cylinder x Flexible hose bolt
 

30
 

310
 

22
\
 \
Rear disc brake torque plate x Axle carrier 104 1,065 77
\
 \
Rear disc brake cylinder installation bolt 34 350 25
\
 
\

\
Rear disc brake x Flexible hose union bolt 

30 

310 

22
\
 \
Parking brake lever x Floor 59 600 43
\
 \
Parking brake cable No.1 x Floor 9 80 69 in.
Vlbf
\
 \
Parking brake cable retainer x Floor 5.4 55 48 in. Vlbf\
 
\

\
Parking brake cable clamp x Floor
 

19
 

190
 

14
\
 \
ABS actuator x Actuator bracket 5.4 55 48 in.
Vlbf
\
 \
ABS actuator bracket x Body 19 195 14
\
 
\

\
Front speed sensor installation bolt 

7.8 

80 

69 in.
Vlbf
\
 \
Rear speed sensor installation bolt 7.8 80 69 in. Vlbf
\
 \
TRAC pump bracket x Body 19 195 14
\
 \
TRAC pump or accumulator x Union bolt 46 465 34
BR±230±
BRAKE SYSTEM SERVICE SPECIFICATIONS
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GENERAL DESCRIPTION
BR03E±06
1. Care must be taken to replace each part properly as it could affect the \
performance of the brakesystem and result in a driving hazard. Replace the parts with parts of the same part number or
equivalent.
2. It is very important to keep parts and the area clean when repairing the\
brake system.
3. If the vehicle is equipped with a mobile communication system, refer to the precaution \
in the IN section.
DESCRIPTION
BR03F±03
The service brakes consist of a foot brake which changes rotational energy to therma\
l energy to stop the
vehicle while it is being driven and a parking brake to keep the vehicle from m\
oving while it is parked.
OPERATION
FOOT BRAKE
BR03G±06
When the brake pedal is depressed, a vacuum builds up in the booster whi\
ch amplifies the pedal force,
pressing on the piston in the master cylinder. The piston movement raises the hydraulic pressure in the
cylinder. This hydraulic pressure is then applied to each respective brake cylin\
der, and acts to press the
brake pads against the rotating discs. The resulting friction converts the ro\
tational energy to thermal ener-
gy, stopping the vehicle.
BR±2±
BRAKE SYSTEM OPERATION
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GENERAL DESCRIPTION
BR03E±06
1. Care must be taken to replace each part properly as it could affect the \
performance of the brakesystem and result in a driving hazard. Replace the parts with parts of the same part number or
equivalent.
2. It is very important to keep parts and the area clean when repairing the\
brake system.
3. If the vehicle is equipped with a mobile communication system, refer to the precaution \
in the IN section.
DESCRIPTION
BR03F±03
The service brakes consist of a foot brake which changes rotational energy to therma\
l energy to stop the
vehicle while it is being driven and a parking brake to keep the vehicle from m\
oving while it is parked.
OPERATION
FOOT BRAKE
BR03G±06
When the brake pedal is depressed, a vacuum builds up in the booster whi\
ch amplifies the pedal force,
pressing on the piston in the master cylinder. The piston movement raises the hydraulic pressure in the
cylinder. This hydraulic pressure is then applied to each respective brake cylin\
der, and acts to press the
brake pads against the rotating discs. The resulting friction converts the ro\
tational energy to thermal ener-
gy, stopping the vehicle.
BR±2±
BRAKE SYSTEM OPERATION
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CHECK AND ADJUSTMENT
BR0EC±07
BRAKE PEDAL CHECK AND
ADJUSTMENT
1. CHECK THAT PEDAL HEIGHT IS CORRECT
Pedal height from asphalt sheet:150.4±160.4 mm (5.92±6.31 in.)
If the pedal height is incorrect, adjust it.
2. IF NECESSARY, ADJUST PEDAL HEIGHT
(a) Disconnect the connector from the stop light switch.
(b) Loosen the stop light switch lock nut and remove the stop light switch.
(c) Loosen the push rod lock nut.
(d) Adjust the pedal height by turning the pedal push rod.
(e) Tighten the push rod lock nut.
Torque: 25 N Vm (260 kgf Vcm, 19 ft Vlbf)
(f) Install the stop light switch and turn it until it lightly contacts
the pedal stopper.
(g) Turn the stop light switch back one turn.
(h) Check the clearance (A) between stop light switch and pedal.
Clearance:
0.5±2.4 mm (0.02±0.09 in.)
(i) Tighten the stop light switch lock nut.
(j) Connect the connector to the stop light switch.
(k) Check that the stop lights come on when the brake pedal isdepressed, and go off when the brake pedal is released.
(l) After adjusting the pedal height, check the pedal free±play.
HINT: If clearance (A) between the stop light switch and the
brake pedal stopper has been adjusted correctly, the pedal
freeplay will meet the specifications.
3. CHECK THAT PEDAL FREEPLAY IS CORRECT, AS SHOWN
(a) Stop the engine and depress the brake pedal several times until there is no more vacuum left in the booster.
(b) Push in the pedal by hand until the beginning of the second point of resistance is felt, then measure the distance, as
shown.
Pedal freeplay:
1±6 mm (0.04±0.24 in.)
If incorrect, check the stop light switch clearance. And if the
clearance is OK, then troubleshoot the brake system.
HINT: The freeplay to the first point of resistance is due to the
play between the clevis and pin. It is 1±3 mm (0.04±0.12 in.)
on the pedal.
±
BRAKE SYSTEM CHECK AND ADJUSTMENTBR±7
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4. CHECK THAT PEDAL RESERVE DISTANCE IS CORRECT,
AS SHOWN
Release the parking brake.
With the engine running, depress the pedal and measure the
pedal reserve distance, as shown.
Pedal reserve distance at 490 N (50 kgf, 110.2 lbf):
More than 89 mm (3.50 in.)
If the reserve distance is incorrect, troubleshoot the brake
system.
BRAKE BOOSTER OPERATIONAL TEST
BR03P±0B
1. OPERATING CHECK
(a) Depress the bake pedal several times with the engine off and
check that there is no change in the pedal reserve distance.
(b) Depress the brake pedal and start the engine. If the pedal goes down slightly, operation is normal.
2. AIR TIGHTNESS CHECK
(a) Start the engine and stop it after 1 or 2 minutes. Depress the brake pedal several times slowly. If the pedal goes down the
farthest the 1st time, but gradually rises after the 2nd or 3rd
time, the booster is air tight.
(b) Depress the brake pedal while the engine is running, and stop the engine with the pedal depressed. If there is no
change in the pedal reserve travel after holding the pedal for
30 seconds, the booster is air tight.
BRAKE SYSTEM BLEEDING
BR0ED±04
HINT: If any work is done on the brake system or if air in the
brake lines is suspected, bleed the system of air.
NOTICE: Do not let brake fluid remain on painted sur-
faces. Wash it off immediately.
1. REMOVE RESERVOIR CAP Turn the reservoir cap to the ªopenº side and remove it.
2. FILL RESERVOIR WITH BRAKE FLUID
Fluid: SAE J1703 or FMVSS NO.116DOT3
BR±8±
BRAKE SYSTEM CHECK AND ADJUSTMENT
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3. BLEED MASTER CYLINDERHINT: If the master cylinder has been disassembled or if the
reservoir becomes empty, bleed the air from the master cylin-
der.
(a) Disconnect the brake lines from the master cylinder.
(b) Slowly depress the brake pedal and hold it.
(c) Block off the outer holes with your fingers, and release the brake pedal.
(d) Repeat (b) and (c) 3 or 4 times.
4. BLEED BRAKE LINE
(a) Connect the vinyl tube to the brake caliper.
(b) Depress the brake pedal several times, then loosen the
bleeder plug with the pedal held down.
(c) At the point when fluid stops coming out, tighten the bleeder plug, then release the brake pedal.
(d) Repeat (b) and (c) until all the air in the fluid has been bled
out.
(e) Repeat the above procedure to bleed the air out of the brake
line for each wheel.
Torque: 11 N Vm (110 kgf Vcm, 8 ft Vlbf)
5. CHECK FLUID LEVEL IN RESERVOIR
Check the fluid level and add fluid if necessary.
Fluid:
SAE J1703 or FMVSS NO.116DOT3
6. INSTALL RESERVOIR CAP
(a) Align the matchmark on the reservoir cap with the matchmark
on the ªopenº side of reservoir.
(b) Push down on the reservoir cap and turn it clockwise until it locks.
(c) Check that the matchmark on the reservoir cap is now aligned with the matchmark on the ªcloseº side of the
reservoir.
±
BRAKE SYSTEM CHECK AND ADJUSTMENTBR±9
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