low oil pressure MAZDA 626 1987 Repair Manual

7C TROUBLESHOOTING
TROUBLESHOOTING
GENERAL NOTE
In the event of a problem with the automatic transaxle, the cause may be in the engine, powertrain,
hydraulic control system, or electrical control system. When troubleshooting, it is recommended to
begin from those points that can be judged quickly and easily. The recommended troubleshooting
sequence is described below.
STEP 1: PRELIMINARY INSPECTION Check preliminary items • ATF level and condition
• Oil leakage • Selector lever position
• Vacuum leakage
• Idle speed and ignition timing
• Tire inflation pressure • Inhibitor switch
This step checks conditions surrounding the automatic
transaxle.
STEP 2: STALL TEST Check engine stall speed This step checks the powertrain.
• Friction element slipping
• Torque converter capacity
STEP 3: TIME LAG TEST Check time lag of oil pressure supply This step checks operation of the hydraulic control system. • Friction elements slipping
• Regulating valves
STEP 4: ROAD TEST Check items on road test
• Shift point • Shift schedule
• Kick-down • Shift shock
This step checks functions of the electrical control system
and hydraulic control system.
STEP 5: OIL PRESSURE TEST Check line pressures and governor pressure This step checks major points of the hydraulic control system.
• Oil pump • Line pressure control • Governer pressure control
By following the above five steps, the cause of the problem should be located.
As another guide to faster location of the causes of problems, the Quick Diagnosis Chart is included
at pages 7C—9 to 7C—11.
In this chart, a circle is used to indicate the components that might be the cause of trouble for 54
types of problems. It is only necessary to check those components indicated by circles, at each step
of the troubleshooting process, in order to quickly locate the cause of the problem.
76G07C-012
7C—8

TROUBLESHOOTING
7C

QUICK DIAGNOSIS CHART
How
to use
Quick Diagnosis Chart
1.
The
numbers indicate
the
order
of
inspection
for
troubleshooting.
2. Circled numbers indicate that
the
transaxle must
be
removed from
the
vehicle.
76G07C-013
Transaxle ON VEHICLE OFF VEHICLE
•

\ Inspection point
\
and
reference
\ page
Condition


7C-25
7C-26
7C-23
10—21
7C—23,24
Section

4A

7C-14
7C—20,22
10—lb
10-12 10—69
7C—5
Section

5

7C—58
7C-62
7C-70
7C-71
7C-55
7C-125
7C-54 7C-71
7C-66,

98

7C-68,

71
\ Inspection point
\
and
reference
\ page
Condition

ATF

level
and
condition

Selector

lever
Inhibitor
switch
and
wiring

^

Vacuum
diaphragm
and

piping

|

Kick-down
solenoid,
kick-down
switch
and
wiring
Engine

idle

speed

and

condition

Engine
stall

speed

Fluid

pressure

(Line

and
governor)
Control
valves

Governor

valve
Band
servo
Transaxle
air
check
Ignition
switch
and
starter
Front
clutch

Rear

clutch
Brake

band

Low

and
reverse
brake

Oil
pump Hydraulic
circuit

Torque

converter

One-way

clutch
Parking

linkage

Planetary
gear

I

Engine

starting
Engine does
not
start
in
N or P
range •
2 3
1

Engine

starting
Engine starts
in
ranges other than
N
and P
ranges •
1 2

Accelerating
Vehicle does
not
move
in
D
range (moves
in 1, 2 & R
ranges) •
• •
•
Accelerating
Vehicle does
not
move
in
forward ranges (moves
in R
range)
Ex-
tremely poor acceleration •
• 5
• •
© •
•
• ©
•
• •
•
Accelerating
Vehicle does
not
move
in R
range (moves
in
forward range) Extremely poor acceleration 1
2 •
•
• •
•
3 4
•
• 5
• ©
© •
©
• ©
•
• •
•
Accelerating
Vehicle does
not
move
in any
range 1
2 •
•
• •
•
3 4
•
• 5
• •
• •
•
© ©
•
• ©
•
Accelerating Slippage felt when accelerating 1
2 •
6
• •
•ST
CO
•
•
• 5
• •
• •
•
© ©
•
• •
• Accelerating
Vehicle moves
in
N
range
Accelerating
Excessive creep
Accelerating
No creep
at all
©
© •
•
© ©
•
• •
•
Accelerating
Low maximum speed
and
poor acceleration 1
2 •
•
• 7
3
4 6
•
5 •
• ©
© ©

No shifting

Does
not
shift from
1
st to 2nd
•
1 •
2
3 •
•
• 4
5
6 7
• •
© ©
•
• ©
•
• •
•

No shifting
Does
not
shift from
2nd to 3rd
•
1 •
2
3 •
•
• 4
5
6 7
•

No shifting

Does
not
shift from
3rd to 2nd
1
• •
2
• •
•
• 3
4
5 6
• ©
• ©
•
• ©
•
• •
•
76G07C-014
7C-9

7C TROUBLESHOOTING
ON VEHICLE OFF VEHICLE
-

\ Inspection point
\ and reference
\ page
Condition


LO
(O
CO CJ OJ CM I
I I
O
O
CJ
r-~
r—
7C-27
7C—23,24
Section

4A

7C—14
7C—20,22
7C-75

CO
O)
in
I
I I
o
o o
r—
r—
Section

5
CO CO
o
WON I
I I
o
o o
1— 1—
m i-
in co
S
IO
i-
1
1 1
o
o o
—
I—
7C—54
7C-71
7C-66,

98

7C—68,

71
\ Inspection point
\ and reference
\ page
Condition

A.TF

level
and

condition

Selector
lever
Inhibitor
switch
and
wiring

Vacuum

diaphragm
and

piping

Kick-down

solenoid,

kick-down

switch
and

wiring

Engine

idle
speed
and
condition
Engine
stall
speed
Fluid
pressure
(Line
and
governor)

Control

valves

Governor

valve
Band
servo

Transaxle

air
check
Ignition
switch
and

starter

Front

clutch

Rear

clutch

Brake

band

Low

and
reverse
brake
Oil pump Hydraulic
circuit
Torque
converter

One-way

clutch

Parking

linkage
Planetary
gear

No
shifting

Does
not
shift from 2nd
to
1
st or from
3rd to
1
st 1
• •
2
• •
•
• 3
4
5 6
•
No
shifting

Does
not
kick-down when accelerator
is
depressed
in 3rd
within
the
kick-down range 1
• •
3
2*
•
• 4
5
• •
• •
• ©
•
• ©
•
• •
•
No
shifting
Excessive engine speed when accelerated
in 3rd
due
to
delayed kick-down 5
• 6
• ©
• •
•
• ©
•
• •
• No
shifting

Does
not
shift from
3rd to 2nd
on
D to
2
range shift 1
2 •
5
6 •
• ©
• ®
•
• ®
•
• •
•
No
shifting

Does
not
shift from
3rd to 2nd
on
D to 1
range shift 5
7 6
• ©
• ®
•
• ®
•
• •
•

Shift

shock

Excessive
N to
D
range shift shock •
• •
2
• 1
•
3 4
•
• •
• •
© •
•
• •
•
• •
•

Shift

shock

Excessive
1
st
to
2nd shift shock 1
• •
2
• •
3
• 4
•
5 6
• •
• ©
•
• •
•
• •
•

Shift

shock

Excissive 2nd
to 3rd
shift shock •
• •
1
• •
•
2 3
•
4 5
• ©
• ©

Shift

shock

Vehicle braked when shifted from
1
st
to 2nd

Shift

shock
Vehicle braked when shifted from 2nd
to 3rd
1
• •
•
• •
•
• 3
.
2 •
•

Shift

shock

Vehicle braked when shifted
to
R range 1
• •
•
• •
•
• •
•
3 2
• •
© ©
•
• •
•
• ©
•
Shift

shock

Shift shock felt when accelerator
is
released
and
deceleration occurs •
1 •
2
3*
•
4 5
6
• •
• •
• •
•
• ©
•
• *
•

Shift

shock

Excessively large 2nd
to 1st
shift shock
in 1
range 1
• •
2
• •
3
4 5
•
• •
•
Shift

point

Excessively high
1st to 2nd
and 2nd
to
3rd shift 1
• •
2
3 •
•
4 5
6
• •
•
Shift

point

Excessively high
3rd to 2nd
and
2nd to
1
st shift point •
1 •
2
3 •
•
4 5
6
• •
• •
• •
•
• ©
•
• •
•
Shift

point
Kick-down operates
or
engine overruns when depressing
ped-
al
in 3rd
beyond kick-down speed limit
1
2 •
3
• •
•
4 5
6
• 7
•

Shift
sequence

Shifts directly from 1st
to 3rd
1
• •
•
• •
•
• 2
3
• 4
• •
• ©
•
• ©
•
• •
•

Shift
sequence
Shifts from
2nd to 1st or
2nd
to
3rd
in
2
range •
1 •
•
• •
•
2 3
•
• •
•
7C-10

TROUBLESHOOTING
7C

ON VEHICLE -OFF VEHICLE
-

\ Inspection point
\
and
reference
\ page
Condition


in cd
ra
CM CM CM
I
I I
o
o o
I—
r~—
r—
7C—27
7C—23,24
Section
4A

7C—14
7C—20,22
7C-75

CM
0>
[—
CO
LO I
I I
O
O O
r^ r—
Section

5
CD CM
O
in (D
s
I
I I
o
o o
r—
r^

w
CM
r-
m f-
I
I I
o
o o
r-— I—
r-—
7C—54
7C-71
7C—66,

98

7C-68,

71 \ Inspection point
\
and
reference
\ page
Condition

ATR

level
and
condition

Selector

lever

Inhibitor

switch
and
wiring

Vacuum

diaphragm
and
piping

Kick-down
solenoid,
kick-down
switch

and

wiring

Engine

idle

speed

and
condition
Engine
stall

speed

Fluid

pressure
(Line
and
governor)
Control
valves

Governor

valve
Band
servo

Transaxle

air
check
Ignition
switch
and

starter

Front
clutch

Rear

clutch

Brake

band

Low
and

reverse

brake
Oil
pump
Hydraulic
circuit

Torque

converter

One-way

clutch
Parking
linkage

Planetary

gear

Snift
sequence

Shifts from
1st to
2nd
or
2nd
to
3rd
in 1
range

Slipping

Practically
no
shift shock,
or
slip-page while 1st
to
2nd shifting 1
2 •
3
• •
•
4 5
•
7 6
• •
• ©
•
• ©
•
• •
•

Slipping

Pracatically
no
shift shock
or
slip-page while 2nd
to
3rd shifting 1
2 •
3
• •
•
4 5
•
7 6
•

Slipping

No shift shock
or
engine runaway
in 1 to 2
range shift 1
2 •
3
• 4
5
• 6
•
• 7
• •
• ©
•
© •
•
• •
•
Slipping

Engine runaway
or
slip when shifting
3rd to 2nd
1
• •
2
• •
•
3 4
•
5 6
• ®
• ©
•
• ®
•
• •
•

Slipping

Slippage evident when vehicle starts moving 1
2 •
5
• •
•
3 4
•
• 6
• •
• •
•
® ©
•
• •
•

Noise

Transaxle noisy
in P and N
range

Noise
Transaxle noisy
in D, 2, 1 and
R ranges •
(D •
•
© •
•
© •
©

Others

No engine brake
in 1
range •
1 •
•
• •
•
2 3
•
• 4
• •
• •
©
• ©
•
• •
•

Others

Vehicle moves
in P
range
or
parking gear
not
disengaged when
P
range disengaged
•

Others
Transaxle overheats 3
4 5
•
2 6
• ®
©
(D ©
© ©
©
• •
©
Others

White smoke from exhaust while running 1
• •
2
• •
3
4 5
•
• 6
• ®
© ©
©
© ©
©
• •
@

Others

Abnormal odor from
oil
level gauge pipe ©
® ©
©
© ®
©
• •
©
76G07C-016
Differential
Problem Probable Cause Remedy Page
Noise Insufficient fluid Add 7C—25
Low fluid quality Replace with specified
ATF
7C-25
Worn bearing Adjust
or
replace 7C-79
Contact surface
of
gears worn Replace 7C-79
Tooth surface
of
gears damaged Replace 7C-79
Contaminated
ATF
Repair
or
replace 7C-25
Differential gear damaged, excessive backlash Replace 7C-79
Excessive bearing preload Adjust 7C—94
76G07C-017
7C—11

7C TROUBLESHOOTING
Evaluation
Condition Possible cause
Worn oil pump
In all ranges Insufficient line
pressure
Oil leakage from oil pump, control
valve, and/or transaxle case
Stuck pressure regulator valve
In D, 2, and 1 Rear clutch slipping
Above specification In D range only One-way clutch slipping
In 2 range only Brake band slipping
Low and reverse brake slipping
Brake band slipping
In R range only Road test to determine if cause is low and reverse brake or reverse clutch:
a) Engine braking in 1 range Front clutch b) No engine braking in 1 range .... Low and reverse brake
Within specification All shift control elements within transaxle functioning normally
Below specification Engine out of tune Below specification
One-way clutch slipping within torque converter
76G07C-026
7C—16

7C TROUBLESHOOTING
STEP 5 (OIL PRESSURE TEST)
This step determines line pressure, and governor pressure to check the hydraulic components and
for oil leakage.
Line Pressure Test
Preparation
1. Connect the SST to the line pressure output point.
2. Connect a tachometer to the engine.
3. Follow the test preparation procedure show in STEP 2 (STALL TEST).
Procedure
76G07C-030
1. Start the engine and verify that the idle speed is 950-5° rpm.
2. Shift the selector lever to D range.
3. Read the line pressure at idle.
4. Depress the brake pedal firmly with the left foot, and gradually depress the accelerator pedal with
the right foot.
5. Read the line pressure as soon as the engine speed becomes constant; then release the accelera-
tor pedal.
Caution
Steps 4 to 5 must be done within 5 seconds.
5. Shift the selector lever to N range and let the engine idle for one minute or more.
6. Read the line pressure at idle and engine stall speeds for each range in the same manner.
7C—20

TROUBLESHOOTING 7C
Specified line pressure:
Range Pressure kPa (kg/cm2, psi) Range
Idle Stall
D 294-392 (3-4, 43-57) 883-1079 (9—11, 128-156)
2 785—1177 (8—12, 114—171) 785-1177 (8—12, 114-171)
1 294-392 (3-4, 43—57) 883-1079 (9—11, 128—156)
R 392-687 (4-7, 57-100) 1570—1864 (16—19, 228-270)
76G07C-031
Evaluation
Condition Possible cause
Below standard
In all ranges
Worn oil pump
Below standard
In all ranges Fluid leakage from the oil pump, control valve, or transaxle case
Below standard
In all ranges
Stuck pressure regulator valve Below standard
In D, 1, 2 ranges Fluid leakage from the rear clutch or governor hydraulic circuit, or both
Below standard
In R range only Fluid leakage from the low and reverse brake hydraulic circuit
Excessive line pressure at idle Leaking or disconnected vacuum hose Excessive line pressure at idle
Leaking vacuum diaphragm
76G07C-032
76G07C-033
Vacuum
gauge Line
pressure
Governor pressure
At Atmosphere Radical line Read
& 200 mmHg pressure governor
(7.87 inHg) reduction
Line Pressure Cutback Point
1. Connect the SST to the line pressure output point
and the governor pressure output point in the trans-
axle case, and place the gauges inside the vehicle.
2. Disconnect the hose to the vacuum diaphragm,
and plug it.
3. Connect a vacuum pump to the vacuum di-
aphragm, and place the pump inside the vehicle.
4. Gradually accelerate the vehicle in D range.
5. Read the governor pressure at the point where the
line pressure suddenly drops.
6. Apply 200 mmHg (7.87 inHg) vacuum, and re-
peat steps 4 and 5.
Standard
Vacuum mmHg (InHg) Governor pressure kPa (kg/cm2, psi)
Atmospheric pressure 98-157 (1.0—1.6, 14-23)
200 (7.87) 39-98 (0.4-1.0, 6—14)
Evaluation
Incorrect pressures
1. Missing diaphragm rod or rod length incorrect, or
both.
2. Stuck valve in control valve.
76G07C-034
7C—21

INSPECTION AND REPAIR 7C
CONTROL VALVE BODY
Precaution
(1) Pay close attention when handling the control valve because it consists of the most precise and
delicate parts of the transaxle.
(2) Neatly arrange the removed parts in order to avoid mixing up similar parts.
(3) Disassemble the control valve assembly and thoroughly clean it when the clutch and/or brake
bands are burned, and/or when the automatic transaxle fluid is degenerated.
Disassembly
Disassemble in the sequence shown in the figure.
2.5—3.4 N m _ (25—35 cm-kg, (7) 22—30 in-lb)
2.5—3.4 N-m (25—35 cm-kg 22—30 in-lb)
. 2.5—3.4 N-m (25—35 cm-kg, 22—30 In-lb)
2.5—3.4 N-m (25—35 cm-kg, 22—30 in-lb)
5—7 N-m {50—70 cm-kg, 43—61 In-lb)
2.5—3.4 N-m (25—35 cm-kg, 22—30 in-lb)
2.5—3.4 N-m (25—35 cm-kg, 22—30 in-lb)
5—7 N-m (50—70 cm-kg, 43—61 in-lb)
^ - 3—4 N-m (30—40 cm-kg, 26—35 in-lb)
76G07C-201
1. Manual valve
2. Oil strainer
3. Lower body
4. Separator plate
5. Throttle relief ball and
spring
6. Orifice check valve and
spring
7. Sub-body
8. Orifice check valve
9. Side plate
10. Vacuum throttle valve
11. Spring
12. Throttle backup valve
13. Downshift valve
14. Spring
15. Side plate
16. Modifier valve
17. 2-3 shift valve
18. Spring
19. 2-3 shift plug
20.1-2 shift valve
21. Spring
22. Side plate
23. Spring
24. Second lock valve
25. Pressure regulator sleeve
26. Pressure regulator plug
27. Spring seat
28. Spring
29. Pressure regulator valve
30. Upper body
7C-75

7C INSPECTION AND REPAIR
Inspection
Check the following and replace any faulty parts.
1. Damaged or worn valves
2. Damaged oil passage
3. Cracked or damaged valve body
4. Operation of each valve
5. Weakened spring 76go7c-2o2
Spring
Name Outer dia. mm (in) Free length mm (in) Wire dia. mm (in)
Throttle backup 7.3 (0.287) 36.0 (1.417) 0.8 (0.031)
Downshift 5.55 (0.219) 21.9 (0.862) 0.55 (0.022)
2-3 shift 6.9 (0.272) 41.0 (1.614) 0.7 (0.028)
1-2 shift 6.4 (0.252) 31.63 (1.245) 0.4 (0.016)
Second lock 5.55 (0.219) 33.5 (1.319) 0.55 (0.022)
Pressure regulator 11.7 (0.461) 43.0 (1.693) 1.2 (0.047)
Throttle relief 7.0 (0.276) 11.2 (0.441) 0.9 (0.035)
Orifice check 5.0 (0.197) 15.5 (0.610) 0.23 (0.009)
76G07C-203
Valve Location
63U07B-500
7C-76

HYDRAULIC CIRCUIT 7C
HYDRAULIC CIRCUIT
OUTLINE
The flow of the individual hydraulic circuits are identified as listed below.
(Numbers indicate individual circuits)
Line pressure source 7
Control element operation system line pressure.... 1,2,3,4,5,6,7,8,9,10,11,12
Auxiliary line pressure 13
Throttle system pressure 16,17,18,19
Governor system pressure 15
Torque converter system pressure 14
1. Line pressure
The line pressure is the hydraulic pressure of the oil emitted from the oil pump after adjustment
by the pressure regulator valve.
2. Throttle pressure
Derived from the line pressure, the throttle pressure is the hydraulic pressure generated by the throttle
valve which operates in conjunction with the intake manifold vacuum.
3. Governor pressure
Also derived from the line pressure, the governor pressure is the hydraulic pressure which varies
in conjuction with the vehicle's speed. It is controlled by the governor rotating together with the out-
put shaft.
Note
Schematic symbols
X : Drain
Orifice
76G07C-338
7C-125