1988 PONTIAC FIERO Service Repair Manual

582.2 POWER HEAD ASSEMBLY
GENERAL DESCRIPTION
This booster is a tandem vacuum suspended unit.
In a normal operating mode, with the service brakes in
the released position, the tandem vacuum suspended
booster operates with vacuum on both sides of its
diaphragms. When the brakes are applied, air at
atmospheric pressure is admitted to one side of each
diaphragm to provide the power assist. When the
service brake is released, the atmospheric air is shut off
from the one side of each diaphragm. The air is then
drawn from the booster through the vacuum check
valve to the vacuum source.
important
e Replace all components included in repair kits
used to service this booster.
e Lubricate rubber parts with silicone grease,
provided in kits, to ease assembly.
o Do not use lubricated shop air on brake parts as
damage to rubber parts may result.
o If any hydraulic component is removed or
disconnected, it may be necessary to bleed all or
part of the brake system.
e The torque values specified are for dry,
unlubricated fasteners.
Perform service operations on a clean bench free
from all mineral oil materials.
ON-CAR SERVICE
BOOSTER ASSEMBLY
(Figure 2)
Remove or Disconnect
1. Master cylinder attaching nuts (37).
2. Master cylinder (34) from booster (35).
3. Booster pushrod (32) from brake pedal.
4. Booster attaching nuts (36) and booster (35).
See NOTICE on page 5 1.
MASTER CYLINDER
BOOSTER
NUT
BOOSTER
Figure 2 Removing Booster Assembly
Install
or Connect
1, Booster (35) and attaching nuts (36) to 21 N*m
(15 lb-ft).
2. Booster pushrod (32) to brake pedal.
3. Master cylinder (34) to booster (35) and
attaching nuts (37) to
27 N-m (20 lb-ft).
EXTERIOR COMPONENTS
(Figure 3)
Important
The vacuum check valve, grommet and front
housing seal can be inspected and/or serviced without
removing the booster from the vehicle.
Remove or Disconnect
1. Booster (35)
as previously described.
2. Boot (1) and silencer (2).
3. Vacuum check
valve (3) and grommet (4).
4. Front housing seal (7).
Inspect
e Boot, front housing seal, and grommets for:
s Cuts
s Nicks
s Excessive wear
e Replace part(s) if any of the above are found.
Above parts in clean denatured alcohol.
Dry with unlubricated compressed air.
See NOTICE on page 5-1.
Install or Connect
e Lubricate inside and outside diameters of grommet
(4) and front housing seal
(7) with a thin layer of
silicone grease.
1. Grommet (4) and vacuum check valve (3).
2. Front housing seal (7).
3. Silencer (2) and boot (1).
4. Booster (35) as previously described.
UNIT REPAIR
BOOSTER
Tool Required:
J 23456 Power Brake Booster Disassembly
and Reassembly Tool
(Figures 4 thru 6)
Disassemble
1. Booster (35) as previously described.
2. Scribe a mark on front and rear housings (10 and
9) to aid reassembly.
3. Using Tool
J 23456 (39), apply force in a
counter-clockwise direction to unlock housings
(9
and 10).
4. Return spring
(1 1) and power piston group (38).

POWER HEAD ASSEMBLY 5D2-3
1. BOOT 6. GROMMET 2. SILENCER 7. FRONT HOUSING 3. VACUUM CHECK SEAL VALVE 35. BOOSTER
Figure 3 Exterior Components
5. Primary piston bearing (8) from rear housing (9).
Inspect
e Front and rear housings:
e Corrosion
e Cracks
e Distortion
e Excessive wear
e Use crocus cloth to polish away minor corrosion.
e Power piston bearing for:
e Cuts
e Nicks
e Replace if damaged.
Clean
e Above parts in clean denatured alcohol.
e Dry with unlubricated compressed air.
Assemble
1. Lubricate inside and outside diameters of
primary piston bearing (8) with silicone grease,
P/N 1052863 or equivalent.
2. Primary piston bearing (8) into rear housing (9).
3. Power piston group (38) into rear housing (9).
4. Return spring (1 1).
5. Align scribe marks on housings (9 and 10).
6. Using tool
J 23456 (39), apply force in a
clockwise direction to lock front and rear
housings (10 and 9).
8. PRIMARY PISTON BEARING 9. REAR HOUSING 10. FRONT HOUSING 11. RETURN SPRING 38. POWER PISTON
Figure 5 Booster Inner Components
e Stake housing after locking. Stake two tabs
180 degrees apart.
e Do not stake a tab that has been previously
staked.
e Assembly can be aided by connecting a
vacuum source to the booster.
7. Booster as previously described.
POWER PISTON GROUP
Tool Required:
J 28458 Retainer Installer (Power Piston
Seal Protector)

6D2-4 POWER HEAD ASSEMBLY
STAKE
I STAKING TAB SOCKET WITH SCREWDRIVER
Figure 6 Staking Procedure
(Figures 7 thru 1 1)
(.+g Disassemble [I]
1.
Remove booster (35) and disconnect housings (9
and 10) as previously described.
2. Piston rod
(12), reaction retainer (13) and power
head silencer (14).
3. Power piston assembly (41) along with pushrod
(32).
e Grasp assemby at outside edge of housing
divider (19) and diaphragms (16 and 20).
e Hold with pushrod (32) down against a
hard surface.
e Use a slight force or impact to dislodge
diaphragm retainer (15).
4. Primary diaphragm (16) and primary support
plate (17) from housing divider (19).
5. Primary diaphragm (16) from primary support
plate (17).
6. Secondary diaphragm (20) and secondary
support plate (21) from housing divider (19).
7. Secondary piston bearing (18) from housing
divider (19).
8. Secondary diaphragm (20) from secondary
support plate
(2 1).
e Parts for:
e Corrosion
e Nicks
e Cracks
e Cuts
e Scoring
e Distortion
e Excessive wear
e Use crocus cloth to polish away minor corrosion
to diaphragm supports, or housing divider.
@ All parts in clean denatured alcohol.
e Do not immerse power piston and pushrod
assembly in alcohol, rather wipe clean with an
alcohol dampened cloth.
e Dry with unlubricated compressed air.
Assemble
1. Lubricate inside diameter of secondary
diaphragm (20) lip, inside diameter of primary
diaphragm (16) lip and secondary piston bearing
(18) with a thin layer of silicone grease.
2. Secondary diaphragm (20) into secondary
support plate (21).
3. Secondary diaphragm (20) and support plate (21)
over power piston assembly (41) and
pushrod
(32). Use J 28458 as a guide to protect the power
piston.
4. Secondary piston bearing (18) into housing
divider (19) with flat surface of bearing on same
side as six raised lugs on divider.
5. Secondary piston bearing (18) and housing
divider (19) over power piston assembly (41) and
pushrod (32). Use J 28458 as a guide.
6. Primary diaphragm (16) into primary support
plate (17).
7. Fold primary diaphragm (16) up, away from
primary support plate (17).
8. Primary diaphragm (16) and support plate (17)
over power piston assembly (41) and
pushrod
(32).
9. Fold primary diaphragm (16) back into position
and pull diaphragm
OD over formed flange of
housing divider (19).
e Check that beads on secondary diaphragm
(20) are seated evenly around complete
circumference.
10. New diaphragm retainer (15) and seat using
J
28458 Retainer Installer.
11. Silencer
(14), reaction retainer (13) and piston
rod (12).
12. Reassemble booster as previously described.
POWER PISTON OVERHAUL
Tools Required:
J 29282 Air Valve Push Rod Retainer
Installer
(Figures 12 thru 14)
+++ Disassemble GI
1. Reaction body retainer (24).
2. Reaction body (25).

POWER HEAD ASSEMBLY 5D2-5
17. PRIMARY SUPPORT 32 PLATE 18. SECONDARY PISTON
12. PISTON ROD
(GAGED)
13. REACTION
RETAINER
14. POWER HEAD Sl LENCER 15. DIAPHRAGM
RETAINER
16. PRIMARY BEARING
19. HOUSING
DIVIDER 20. SECONDARY
DIAPHRAGM
21. SECONDARY
SUPPORT PLATE
32. PUSHROD 41. POWER PISTON
ASSEMBLY
DIAPHRAGM
HM0007-5D2-AB
Figure 7 Power Piston Group
DIAPHRAGM
20. SECONDARY
DIAPHRAGM 4 1 21. SECONDARY
SUPPORT PLATE
41. POWER PISTON
ASSEMBLY
42. TOOL J28458
Figure 8 Assembling Secondary Diaphram & Support
18. SECONDARY PISTON 41. POWER PISTON
BEARING ASSEMBLY
19. HOUSING DIVIDER 42. TOOL J28458 20. SECONDARY
Figure 9 Assembling Housing Divider

682-6 POWER HEAD ASSEMBLY
16. PRIMARY DIAPHRAGM
17. PRIMARY SUPPORT PLATE 19. HOUSING DIVIDER 20. SECONDARY
DIAPHRAGM
41. POWER PISTON ASSEMBLY
Figure 10 Assembling Primary Diaphram and Support
A, '15 h 15. DIAPHRAGM RETAINER 32. P'JSHROD
42. TOOL J28458
Figure 11 Sealing Diaphragm Retainer
3. Reaction disc (22) and reaction piston (23) from
reaction body
(25).
4.
Air valve spring (26) and reaction bumper (27)
from end of air valve pushrod (32).
5. Retaining ring (28) from air valve pushrod
assembly (32) using No. 2 Truarc pliers or
equivalent.
6. Air valve pushrod assembly (32) by inserting
screwdriver through
pushrod eyelet and pulling
straight out.
e Considerable force will be required.
7. Filter (29), retainer (30) and O-ring (3 1) from air
valve
pushrod assembly (32).
e Power piston for cracks.
e Rubber parts for cuts or nicks.
Air valve
pushrod assembly for corrosion.
Replace
part(s) if any of the preceding are found.
Clean
All parts in clean denatured alcohol.
e ~r~-with unlubricated compressed air.
22. REACTION DISC 29. FILTER 23. REACTION PISTON 30. RETAINER 24. REACTION BODY 31. O-RING RETAINER 32. AIR VALVE 25. REACTION BODY PUSHROD 26. AIR VALVE SPRING 33. POWER PISTON 27. REACTION BUMPER 28. RETAINING RING
HMO01 2.5D2-A6
Figure 12 Power Piston Assembly
Assemble
Lubricated O-ring (31) onto air valve pushrod
assembly (32).
Air valve pushrod assembly (32) into power
piston
(41).
Retainer (30) and seat using appropriate Retainer
Installer
(44).
Filter (29) over pushrod eyelet into power piston
(41).
Retaining ring (28) onto air valve pushrod
assembly (32) using No. 2 Truarc pliers or
equivalent.
Reaction bumper
(27), air valve spring (26).
Reaction piston (23) and reaction disc (22) into
reaction body
(25).
Reaction body (25).
Reaction body retainer (24).

POWER HEAD ASSEMBLY 5D2-7
30. RETAINER
41. POWER PISTON
ASSEMBLY
44, RETAINER INSTALLER HMO01 3-5D2-AB
Figure 13 Retainer Assembly
GAGING PROCEDURE
Tool Required:
J 22647 Push Rod Height Gage
(Figure 15)
e After assembly of booster, position J 22647 Gage
(43) over piston rod (12).
e If piston rod (12) height is not within GO-NO
GO limits of gage
(43), use a service-adjustable
piston rod to obtain correct height.
12. PISTON ROD 43. GAGE J22647
43 b
Figure 15 Gaging Piston Rod
41. POWER PISTON
ASSEMBLY
44. RETAINER
INSTALLER
HM0014-5D2.AB
Figure 14 Installing Retainer Into Piston

SPECIFICATIONS AND SPECIAL TOOLS
GENERAL SPECIFICATIONS
Item mm In.
Front Disc Brake Rotor
Rotor Diameter.
............................................................. 267.00 10.5
LateralRunout .............................................................. 0.13 0.005
Thicknessvariation .......................................................... 0.013 0.0005
Rotor Thickness (Maximum)
................................................... 26.5 1.043
Minimum Thickness After Refinish
.............................................. 24.84 0.980
*DiscardThickness ........................................................... 24.5 0.965
Rear Disc Brake Rotor
Rotor Diameter.
............................................................. 267.00 10.5
LateralRunout .............................................................. 0.13 0.005
Thickness Variation
.......................................................... 0.01 3 0.0005
Rotor Thickness (Maximum)
................................................... 26.47 1.042
Minimum Thickness After Refinish
.............................................. 25.04 0.986
*DiscardThickness ........................................................... 24.3 0.956
Drums
InsideDiameter ............................................................. 241.00 9.5
Maximum
Rebore Diameter. ................................................... 242.81 9.56
*Discard Diameter.
........................................................... 243.59 9.59
Runout ................................................................ 0.15 0.006
*All brake drums and rotors have a discard dimension cast into them. This is a wear dimension and not a refinish dimension.
Any drum or rotor which does not meet the specification should be replaced.
TORQUE SPECIFICATIONS
Item N-m
BrakePedaltoBracketNut .......................................... 34
Booster to Pedal Bracket Nut.
........................................ 2 1
Master Cylinder to Booster Nut
....................................... 27
Parking Brake Control Assembly to Floor Pan Bolt
........................ 10
Brake Hose to Caliper Bolt
........................................... 45
BrakePipe ....................................................... 15
Caliper Mounting Bolt.
.............................................. 50
Wheel Cylinder Bleeder Valve
........................................ 6
Backing Plate to Axle Housing Nut.
.................................... 58
Caliper Bleeder Valve.
.............................................. 13
Junction Block to Rear Axle Bolt
...................................... 27
InletTubeNut ..................................................... 17
AnchorPinNut .................................................... 140
Master Cylinder to Combination Valve Pipe.
............................. 23
Parking Brake Caliper Lever Nut
...................................... 48
Lbs. Ft. Lbs. In.