Pontiac Fiero 1988 Service Manual page 235

5-14 BRAKES
2. Fasten a dial indicator to the steering knuckle so that
the indicator button contacts the rotor about 1 inch
from the rotor edge.
3. Zero the dial indicator.
4.
Move the rotor one complete revolution and observe
total indicated runout (T.I.R.).
Excessive lateral runout of the rotor can often be impro-
ved by indexing the rotor on the hub one or two bolt posi-
tions from the original position. If the lateral runout cannot
be corrected by indexing the rotor, check the hub and bear-
ing assembly for excessive lateral runout. If the hub and
bearing assembly lateral runout exceeds .040 mm (.0015-
inch), replace the hub and bearing assembly. If lateral
runout is within specifications, see "Rotor Tolerance and
Surface Finish."
A rotor that does not meet the lateral runout specification
should be resurfaced or replaced as necessary.
Rotor Tolerance and Surface Finish
In manufacturing the brake rotor, tolerances of the brak-
ing surfaces for flatness, thickness variation and lateral
runout are held very close. The maintenance of close toler-
ances on the shape of the braking surfaces is necessary to
prevent brake roughness.
In addition to these tolerances, the surface finish must be
held to a specified range. The control of the braking surface
finish is necessary to avoid pulls and erratic performance
and to extend lining life.
Light scoring of the rotor surfaces not exceeding
0.38 mm (0.015-inch) in depth, which may result from nor-
mal use, will not affect brake operation.
Refinishing Brake Rotors
All brake rotors have a minimum thickness dimension
cast into them. This dimension is the minimum wear dimen-
sion and not a refinish dimension. Do not use a brake rotor
that will not meet specifications. See Section 5F.
Since accurate control of the rotor tolerances is neces-
sary for proper performance of the disc brakes, machining
of the rotor should be done only with precision equipment.
When refinishing rotors, always use sharp cutting tools
or bits. Dull or worn tools leave a poor surface finish which
will affect initial braking performance. Vibration dampening
attachments should always be used when refinishing brak-
ing surfaces. These attachments eliminate tool chatter and
will result in better surface finish.
The optimum speed for refinishing braking surfaces is a
spindle speed of 200 rpm. Crossfeed for rough cutting
should range from 0.254-0.152 mm (0.010-0.006-inch) per
revolution. Finish cuts should be made at crossfeeds no
greater than 0.051 mm (0.002-inch) per revolution.
TO R E L E A S E T A B S (B).
J 1 0 0 1 3 - 5 - P
Figure 13 Removing Brake S w i t c h Connector
electrical circuit is faulty. Replace bulb or repair elec-
trical circuit as necessary.
3. When warning lamp lights, turn off ignition switch.
Disconnect jumper and connect wire to switch termi-
nal.
Testing Combination Valve Warning Lamp Switch
1. Attach a bleeder hose to a rear brake bleed screw and
immerse the other end of the hose in a container
partially filled with clean brake fluid. Be sure master
cylinder reservoirs are full.
2. Turn ignition switch to " O N . " Open bleeder screw
while an assistant applies moderate pressure to the
brake pedal. Warning lamp should light. Close
bleeder screw before assistant releases brake pedal.
Apply brake pedal with moderate-to-heavy pressure.
Lamp should go out.
3. Attach the bleeder hose to a front brake bleeder
screw and repeat steps 1 and 2. Warning lamp action
should be the same as in step 2. Turn off ignition
switch.
4. If warning lamp does not light during steps 2 and 3,
but does light when a jumper is connected to ground,
the warning lamp switch portion of the combination
valve is faulty. Do not disassemble the combination
valve. If any portion of the combination valve is faulty,
it must be replaced with a new combination valve.
C O M B I N A T I O N V A L V E
Testing Combination Valve Electrical Circuit (Figure 13)
When removing the electrical wire connector from the
pressure differential switch, squeeze the eliptical shaped
plastic locking ring and pull up. This will move the locking
tangs away from the switch. Pliers can be used to help
remove the connector.
1. Disconnect wire from switch terminal and use a
jumper to connect wire to a good ground.
2. Turn ignition key to " O N . " The warning lamp should
light. If lamp does not light, bulb is burned out or
4-+
Combination Valve Replacement
Remove or Disconnect (Figures 13 and 14)
• The combination valve is not repairable and must be
serviced as a complete assembly.
1. Hydraulic pipes at combination valve.
• Plug pipes to prevent loss of fluid and entrance
of dirt.
2. Wiring harness from valve switch terminal.
3. Bolt attaching valve to bracket.
4. Combination valve.