1987 MAZDA 626 Workshop Manual

MASTER CYLINDER 1 1
Adjustment
Adjust the piston to push rod clearance in the follow-
ing order.
1. For (a) of judgement table
(1) Measure the height of (D) and record after
removing the SST from the master cylinder.
76G11X-028
Adjust nut
(2) Install the SST again to the master cylinder,
and turn the adjust nut so that clearance (C)
between the SST and the master cylinder is
0 mm (Oin).
(3) Measure the height of (E) when clearance (C)
is 0 mm (Oin).
(E) — (D) = Projecting amount of the power
brake unit push rod
76G11X-029
(4) Remove the push rod from the power brake
unit.
63G11X-349
(5) Make the piston to push rod clearance 0 mm
(Oin) by turning the push rod and shortening
the push rod length by the amount of (E) — (D).
Note
The threads of the push rod are specially
designed so that the push rod bolt becomes
harder to turn past a certain point to prevent
loosening of the bolt. Turn the push rod bolt
only within this range when adjusting.
76G11X030
11—25

1 1 MASTER CYLINDER
2. For (b) of the judgement table
(1) Push the push rod of SST lightly by hand until
the push rod end touches the bottom of the pri-
mary piston in the master cylinder.
Note
When pushing only use enough pressure to
bottom the rod in the piston. If too much pres-
sure is applied a false reading will occur.
76G11X-031
(2) Measure clearance (B) between the adjust nut
and the SST body with the rod held down.
(B) = Recessed amount of the power brake
unit push rod
76G11X-032
(3) Remove the push rod from the power brake
unit.
63G11X-353
(4) Make the push rod clearance 0 mm (Oin) by
turning the push rod and lengthening the push
rod length by the amount of (B).
Note
The threads of the push rod are specially
designed so that the push rod bolt becomes
harder to turn past a certain point to prevent
loosening of the bolt. Turn the push rod bolt
only within this range when adjusting.
76G11X-033
11—26

POWER BRAKE UNIT 1 1
86U11X-038
0
o
X
\ V^ Third
Second
^ First
86U11X-039
O X

fiSy

V
86U11X-040
Pedal-depression Pre!tur!9au9e
force gauge
^Intake manifold
86U11X-041
POWER BRAKE UNIT
FUNCTION CHECK
Simple Method
First step
1. With the engine stopped, depress the pedal a few
times.
2. With the pedal depressed, start the engine
3. If immediately after the engine starts the pedal
moves down slightly, the unit is operating.
Second step
1. Start the engine.
2. Stop the engine after it has run for
1
or 2 minutes.
3. Depress the pedal with the usual force.
4.
If
the first pedal stroke is long and becomes short-
er with subsequent strokes, the unit is operating.
5. If a problem is found, inspect for damage of the
check valve or vacuum hose, and examine the in-
stallation condition. Repair if necessary, and inspect
it once again.
Third step
1. Start the engine.
2. Depress the pedal with the usual force.
3. Stop the engine with the pedal still depressed.
4. Hold the pedal down for about 30 seconds.
5. If the pedal height does not change, the unit is
operating.
6. If there is a problem, check for damage to the
check valve or vacuum hose, and check the con-
nection. Repair if necessary, and check once
again.
If the nature of the problem is still not clear after fol-
lowing the 3 steps above, follow the more detailed
check described in "Method using tester".
Method Using Tester
Connect a pressure gauge, vacuum gauge, and ped-
al depression force gauge as shown in the figure. Af-
ter bleeding the air from the pressure gauge, conduct
the test as described in the 3 steps below.
Note
Use commercially available gauges and ped-
al depression force gauge.
11—27

1 1 POWER BRAKE UNIT
a) Checking for vacuum loss
Unloaded condition
1. Start the engine.
2. Stop the engine when the vacuum gauge reading
reaches 500 mmHg (19.7 inHg).
3. Observe the vacuum gauge for 15 seconds.
If
the
gauge shows 475—500 mmHg (18.7—19.7
inHg), the unit is operating.
76G11X-065
Loaded condition
1. Start the engine.
2. Depress the brake pedal with a force of 196 N (20
kg, 44 lb).
3. With the brake pedal depressed, stop the engine
when the vacuum gauge reading reaches 500
mmHg (19.7 inHg).
4. Observe the vacuum gauge for 15 seconds.
If
the
gauge shows 475—500 mmHg (18.7—19.7
inHg), the unit is operating.
76G11X066
b) Checking for hydraulic pressure
1. If with the engine stopped (when vacuum is 0
mmHg) the relation between pedal force and fluid
pressure is within specification, the unit is operating.
Pedal force Fluid pressure
196 N (20 kg, 44 lb) | 1,177 kPa (12 kg/cm2, 171 psi) mia
76G11X-067
2. Start the engine. Depress the brake pedal when
the vacuum reaches 500 mmHg (19.7 inHg).
If the relation between pedal force and fluid pres-
sure is within specification, the unit is operating.
Pedal force Fluid pressure
196 N (20 kg, 44 lb) 7,063 kPa (72 kg/cm2, 1,024 psi) min.
76G11X068
11-28

POWER BRAKE UNIT 1 1
76G11X-034
INSPECTION OF CHECK VALVE
Note (MTX)
The check valve is pressed into the vacuum
hose. There is an arrow on the hose surface
to indicate direction of installation.
Inspection
1. Disconnect the vacuum hose from the engine.
2. Apply suction and pressure to the hose from the
engine side. Check that air flows only toward the
engine.
If the air passes in both directions or not at all, re-
place the check valve (along with the hose).
REMOVAL
Remove in the sequence shown in the figure, referring to removal note for specially marked parts.
1. Fluid level sensor connector
2. Vacuum switch coupler
(RF, RF-CX)
3. Brake pipe
4. Master cylinder
5. Clutch pipe holder
6. Vacuum hose and check
valve
7. Clevis pin
8. Steering shaft
76G11X-069
9. Power brake unit
10. Gasket
11. Locknut
12. Operating lever
11-29

1 1 POWER BRAKE UNIT
Removal Note
Steering Shaft
To remove the mounting nuts of the power brake unit,
the steering shaft must be removed. (Refer to page
10—22 for removal and installation procedures.)
76G11X-102
DISASSEMBLY AND ASSEMBLY
1. Disassemble in the sequence shown in the figure, referring to disassembly note for specially marked
parts.
2. Inspect each part, referring to inspection note.
3. Assemble in the reverse order of disassembly, referring to assembly note for specially marked parts.
8.8—13 N-m (90-130 cm-kg, 78—112 in-lb)
1. Dust boot
2. Rear shell assembly
3. Retainer
4. Bearing
5. Dust seal
6. Retainer
7. Air filters
8. Air silencer
9. Diaphragm and plate
10. Power piston assembly
11. Retainer key
12. Valve rod and plunger as-
sembly
13. Reaction disc
76G11X-070
14. Spring
15. Push rod
16. Front shell assembly
17. Retainer
18. Seal
19. Vacuum switch (RF, RF-CX)
11-30

POWER BRAKE UNIT 1 1
76G11X-071
Disassembly Note
Front and rear shells
1. Secure the front shell studs in a vise after attach-
ing suitable nuts to them to prevent damage to the
studs.
2. Before separating the front and rear shell assem-
blies, make matching marks to be used in reas-
sembly.
3. Fit a wrench onto the rear shell studs; then fasten
two of them with suitable nuts.
4. Rotate the rear shell counterclockwise to unlock.
Caution
The rear shell is spring loaded; loosen it
carefully.
Retainer key
Depress the plunger rod fully; then remove the re-
tainer key.
86U11X-049
86U11X-050
Assembly Note
Application of Grease
Before assembly, coat the parts shown in the figure
with silicon grease.
(1) Entire surface of reaction disc
(2) Dust seal lip
(3) Push rod
(4) Diaphragm-to-shell contacting surfaces
(5) Power piston
(6) Valve plunger oil seal
Retainer key
1. Push down the plunger rod.
2. Align the groove of the valve plunger with the slot
of the power piston.
3. Insert the retainer key.
86U11X-051
11—31

1 1 POWER BRAKE UNIT
Diaphragm
Install the diaphragm to the power piston and plate.
Caution
Check that the diaphragm is well seated in the
groove.
86U11X-052
Rear shell assembly
Assemble the rear shell assembly; carefully guiding
the tube end of the power piston through the dust
seal of the rear shell.
86U11X-053
Front shell and rear shells
Press down the rear shell assembly, and rotate it
clockwise until the matching marks are aligned.
Caution
Fit suitable nuts to two studs of the rear shell
and tighten them to mount the wrench.
76G11X-072
INSPECTION
1. Inspect all rubber parts. Wipe free of fluid and care-
fully inspect all rubber parts for cuts, nicks, and
other damage.
2. Check the power piston for cracks,distortion, chip-
ping, and damaged seats.
3. Inspect the reaction disc rubber for deterioration.
4. Check that the seats of the valve rod and plunger
are smooth and free of nicks and dents.
5. Inspect the front and rear shells for scratches,
scores, pits, dents, and other damage.
6. Check the diaphragm for cuts and other damage.
11—32