1995 SUBARU LEGACY Engine control unit

1. Engine Cooling System
Trouble Possible cause Corrective action
Over-heatinga. Insufficient engine coolantReplenish engine coolant, inspect for leakage, and
repair.
b. Loose timing belt Repair or replace timing belt tensioner.
c. Oil on drive belt Replace.
d. Malfunction of thermostat Replace.
e. Malfunction of engine coolant pump Replace.
f. Clogged engine coolant passage Clean.
g. Improper ignition timingInspect and repair ignition control system.

h. Clogged or leaking radiator Clean or repair, or replace.
i. Improper engine oil in engine coolant Replace engine coolant.
j. Air/fuel mixture ratio too leanInspect and repair fuel injection system.

k. Excessive back pressure in exhaust system Clean or replace.
l. Insufficient clearance between piston and cylinder Adjust or replace.
m. Slipping clutch Repair or replace.
n. Dragging brake Adjust.
o. Improper transmission oil Replace.
p. Defective thermostat Replace.
q. Malfunction of electric fanInspect radiator fan relay, engine coolant temperature
sensor or radiator motor and replace there.
Over-coolinga. Atmospheric temperature extremely low Partly cover radiator front area.
b. Defective thermostat Replace.
Engine coolant
leaks.a. Loosened or damaged connecting units on hoses Repair or replace.
b. Leakage from engine coolant pump Replace.
c. Leakage from engine coolant pipe Repair or replace.
d. Leakage around cylinder head gasket Retighten cylinder head bolts or replace gasket.
e. Damaged or cracked cylinder head and crankcase Repair or replace.
f. Damaged or cracked thermostat case Repair or replace.
g. Leakage from radiator Repair or replace.
Noisea. Defective drive belt Replace.
b. Defective radiator fan Replace.
c. Defective engine coolant pump bearing Replace engine coolant pump.
d. Defective engine coolant pump mechanical seal Replace engine coolant pump.
19
2-5DIAGNOSTICS
1. Engine Cooling System

2. OIL LEAK CHECK PROCEDURE AND
REPLACEMENT PARTS
NOTE:
Parts requiring replacement are described in the smallest
unit of spare parts including damaged parts and spare
parts damaged. In actual disassembly work, accidental
damage as well as inevitable damage to some related
parts must be taken into account, and spare parts for them
must also be prepared. However, it is essential to pinpoint
the cause of trouble, and limit the number of replacement
parts as much as possible.
1) Leakage from“a”
The oil seal is damaged. Replace valve assembly with a
new one.
2) Leakage from“b”
The torsion bar O-ring is damaged. Replace valve assem-
bly with a new one.
3) Leakage from“c”
The oil seal is damaged. Replace valve assembly with a
new one.
4) Leakage from“d”
The pipe is damaged. Replace the faulty pipe or O-ring.
5) If leak is other than a, b, c, or d, and if oil is leaking from
the gearbox, move the right and left boots toward tie-rod
end side, respectively, with the gearbox mounted to the
vehicle, and remove oil from the surrounding portions.
Then, turn the steering wheel from lock to lock 30 to 40
times with the engine running, then make comparison of
the leaked portion immediately after and several hours
after this operation.
6) Leakage from“e”
The cylinder seal is damaged. Replace rack bush with a
new one.
7) Leakage from“f”
There are two possible causes. Take following step first.
Remove the pipe assembly B from the valve housing, and
close the circuit with ST.
ST 926420000 PLUG
Turn the steering wheel from lock to lock 30 to 40 times
with the engine running, then make comparison of the
leaked portion between immediately after and several
hours after this operation.
CAUTION:

If leakage from“f”is noted again:
The oil seal of pinion and valve assembly is damaged.
Replace pinion and valve assembly with a new one. Or
replace the oil seal and the parts that are damaged
during disassembly with new ones.

If oil stops leaking from“f”:
The oil seal of rack housing is damaged.
Replace the oil seal and the parts that are damaged
during disassembly with new ones.
41
4-3SERVICE PROCEDURE
5. Control Valve (Power Steering Gearbox) [LHD model]

2. OIL LEAK CHECK PROCEDURE AND
REPLACEMENT PARTS
NOTE:
Parts requiring replacement are described in the smallest
unit of spare parts including damaged parts and spare
parts damaged. In actual disassembly work, accidental
damage as well as inevitable damage to some related
parts must be taken into account, and spare parts for them
must also be prepared. However, it is essential to pinpoint
the cause of trouble, and limit the number of replacement
parts as much as possible.
1) Leakage from“a”
The oil seal is damaged. Replace valve assembly with a
new one.
2) Leakage from“b”
The torsion bar O-ring is damaged. Replace valve assem-
bly with a new one.
3) Leakage from“c”
The oil seal is damaged. Replace valve assembly with a
new one.
4) Leakage from“d”
The pipe is damaged. Replace the faulty pipe or O-ring.
5) If leak is other than a, b, c, or d, and if oil is leaking from
the gearbox, move the right and left boots toward tie-rod
end side, respectively, with the gearbox mounted to the
vehicle, and remove oil from the surrounding portions.
Then, turn the steering wheel from lock to lock 30 to 40
times with the engine running, then make comparison of
the leaked portion immediately after and several hours
after this operation.
6) Leakage from“e”
There are two possible causes. Take following step first.
Remove the pipe assembly B from the valve housing, and
close the circuit with ST.
ST 926420000 PLUG
Turn the steering wheel from lock to lock 30 to 40 times
with the engine running, then make comparison of the
leaked portion between immediately after and several
hours after this operation.
CAUTION:

If leakage from“e”is noted again:
The oil seal of pinion and valve assembly is damaged.
Replace pinion and valve assembly with a new one. Or
replace the oil seal and the parts that are damaged
during disassembly with new ones.

If oil stops leaking from“e”:
The oil seal of rack housing is damaged.
Replace the oil seal and the parts that are damaged
during disassembly with new ones.
50
4-3SERVICE PROCEDURE
6. Control Valve (Power Steering Gearbox) [RHD model]

Air bleeder tightening torque:
8±1 N⋅m (0.8±0.1 kg-m, 5.8±0.7 ft-lb)
5) Perform these steps for the brakes connecting to the
secondary chamber of master cylinder, first, and then for
the ones connecting to primary chamber. With all proce-
dures completed, fully depress the brake pedal and keep
it in that position for approximately 20 seconds to make
sure that there is no leak evident in the entire system.
G4M0436
6) Perform sequence control. (With ABS model) [W15C1].>
7) Check the pedal stroke.
While the engine is idling, depress the brake pedal with a
490 N (50 kg, 110 lb) load and measure the distance
between the brake pedal and steering wheel. With the
brake pedal released, measure the distance between the
pedal and steering wheel again. The difference between
the two measurements must be more than specified.
Specified pedal stroke:
Without ABS
90 mm (3.54 in)
With ABS
95 mm (3.74 in)
When depressing brake pedal with a 490 N (50 kg,
110 lb) load.
(1) Models without ABS
If the distance is more than specifications, there is a
possibility that air is in the brake line. Bleed air from the
brake line.
(2) Models with ABS
If the distance is more than specifications, there is a
possibility air is in the inside of the hydraulic unit.
Therefore, air must be bled from the inside of the
hydraulic unit to the brake pipes in accordance with the
bleeding sequence control.
8) Add brake fluid to the required level (MAX. level) of
reserve tank.
9) As a final step, test run the vehicle at low speed and
apply brakes relatively hard 2 to 3 times to ensure that
brakes provide normal braking action on all four wheels
without dragging and uneven braking.
56
4-4SERVICE PROCEDURE
11. Air Bleeding (Without TCS model)

15. Hydraulic Unit for ABS System
B4M0069A
1Connector

2Cap

3Motor relay

4Valve relay

5Hydraulic control unit

6Front-RH outlet

7Rear-LH outlet
8Rear-RH outlet

9Front-LH outlet

10Primary inlet

11Secondary inlet

12Bracket
Tightening torque: N⋅m (kg-m, ft-lb)
T1: 1.2±0.2
(0.125±0.025, 0.9±0.2)
T2: 18±5 (1.8±0.5, 13.0±3.6)
T3: 29±7 (3.0±0.7, 21.7±5.1)
T4: 32±10 (3.3±1.0, 24±7)
A: REMOVAL
1) Remove air intake duct.
2) Remove canister from engine compartment to facilitate
removal of hydraulic unit.
3) Disconnect brake pipes from hydraulic unit and plug
open joints to prevent entry of foreign particles.
G4M0455
4) Remove nuts and bolts which secure hydraulic unit, and
remove hydraulic unit from engine compartment.
CAUTION:

Hydraulic unit cannot be disassembled. Do not
attempt to loosen bolts and nuts.

Do not drop or bump hydraulic unit.

Do not turn the hydraulic unit upside down or place
it on its side.
66
4-4SERVICE PROCEDURE
15. Hydraulic Unit for ABS System

2. CHECKING THE HYDRAULIC UNIT OPERATION BY
PRESSURE GAUGE
1) Remove the FL and FR pipes from the hydraulic unit.
G4M0460
2) Connect two pressure gauges to the hydraulic unit.
CAUTION:

Pressure gauges used exclusively for brake fluid
must be used.

Do not employ pressure gauge previously used for
transmission since the piston seal is expanded which
may lead to malfunction of the brake.
3) Bleed air from the pressure gauges.
4) Perform sequence control.
B4M0082A
(1) Connect diagnosis terminals to 3 terminals (K) and
6 terminals (L) of the diagnosis connector beside driver
seat heater unit.
(2) Turn ignition switch ON.
(3) The ABS warning light comes on.
(4) Depress the brake pedal within 0.5 seconds after
the warning light goes out so that the pressure gauge
registers a pressure equal to the initial value.
CAUTION:
Do not depress the clutch pedal.
NOTE:
The engine must not be operating.
68
4-4SERVICE PROCEDURE
15. Hydraulic Unit for ABS System

G4M0462
3. CHECKING THE HYDRAULIC UNIT WITH BRAKE
TESTER
1) In the case of AWD vehicles, install a spare fuse with
the FWD connector in the engine compartment to simulate
FWD vehicles.
B4M0082A
2) Connect diagnosis terminals to 3 terminals (K) and 6
terminals (L) of the diagnosis connector beside driver seat
heater unit.
G4M0464
3) Set the front wheels or rear wheels on the brake tester
and set the select lever’s position at“neutral”.
4) Operate the brake tester.
5) Perform sequence control.
(1) Turn ignition switch ON.
(2) The ABS warning light comes on.
(3) Depress the brake pedal within 0.5 seconds after
the warning light goes out so that the brake tester reg-
isters a pressure equal to the initial value.
CAUTION:
Do not depress the clutch pedal.
NOTE:
The engine must not be operating.
6) Hydraulic unit begins to work; and check the following
working sequence.
(1) The left front wheel performs decompression,
holding, and compression in sequence, and subse-
quently the right front wheel repeats the cycle.
(2) Simultaneously both right and left rear wheel per-
form decompression, holding, and compression in
sequence.
70
4-4SERVICE PROCEDURE
15. Hydraulic Unit for ABS System

7) Read values indicated on the brake tester and check if
the fluctuation of values, when decompressed and
compressed, meet the standard values.
Initial value When decompressed When compressed
Front wheel 1,961 N (200 kg, 441 lb) 245 N (25 kg, 55 lb) 1,961 N (200 kg, 441 lb)
Rear wheel 686 N (70 kg, 154 lb) 245 N (25 kg, 55 lb) 686 N (70 kg, 154 lb)

In case of hydraulic unit plunger piston malfunction:
Initial value When decompressed When compressed
Rear right wheel 686 N (70 kg, 154 lb) 245 N (25 kg, 55 lb) 686 N (70 kg, 154 lb)
Rear left wheel 686 N (70 kg, 154 lb) 686 N (70 kg, 154 lb) 686 N (70 kg, 154 lb)
8) After checking, also check if any irregular brake pedal
tightness is felt.
9) In case of AWD vehicles, remove the spare fuse from
the FWD connector in the engine compartment to return to
the original AWD state.
C: SEQUENCE CONTROL
Under the sequence control, after the hydraulic unit sole-
noid valve is driven, the operation of the hydraulic unit can
be checked by means of the brake tester or pressure
gauge.
B4M0082A
1. OPERATIONAL GUIDELINES OF THE SEQUENCE
CONTROL
1) Connect diagnosis terminals to 3 terminals (K) and 6
terminals (L) of the diagnosis connector beside driver seat
heater unit.
2) Set the speed of all wheels at 4 km/h (2 MPH) or less.
3) Within 0.5 seconds after the ABS warning lamp goes
out, immediately after the ignition switch is turned to on,
depress the brake pedal and hold.
CAUTION:
Do not depress the clutch pedal.
NOTE:

When the ignition switch is set to on, the brake pedal
must not be depressed.

Engine must not operate.
71
4-4SERVICE PROCEDURE
15. Hydraulic Unit for ABS System