Cooling System Specifications & Removal & Installation Subaru Legacy BC/BJ/BF

DESCRIPTION & OPERATION

The engine cooling system consists of a cross-flow radiator which features high heat-dissipation performance, an electric motor fan, a water pump, a thermostat, and a thermometer. (Scheme 1) The reserve tank is designed to eliminate the need for replenishing coolant. On models without A/C, the ECU sends an ON or OFF switch signal to the radiator fan in response to the signals from the thermometer and speed sensor. On models with an air conditioner, the ECU sends ON or OFF, and Lo (low) or Hi (high) switch signals to the radiator fan and A/C fan in response to signals from the thermometer, speed sensor, and A/C switch.

Scheme 1

Non-Turbo Model

This cooling system operates in three steps, depending on the coolant temperature that is flowing through the cooling circuit. (Scheme 2)

1. With thermostat closed - When coolant temperature is below 76°C (169°F), the thermostat remains closed and the coolant flows through the bypass and heater circuits. This permits the engine to quickly warm up.
2. With thermostat opened - When coolant temperature is above 76-80°C (169-176°F), the thermostat opens and the coolant flows through the radiator where it is cooled.
3. With electric cooling fan operating - When coolant temperature rises above 95°C (203°F), the thermometer turns on and the electric cooling fan rotates.

Scheme 2

Turbo Model

Coolant flow is determined by coolant temperature. (Scheme 3)

1. With thermostat closed - When coolant temperature is below 76°C (169°F), the thermostat remains closed and the coolant flows through the bypass and heater circuits. This permits the engine to quickly warm up.
2. With thermostat opened - When coolant temperature is above 76-80°C (169-176°F), the thermostat opens and the coolant flows through the radiator where it is cooled.
3. With electric cooling fan operating - When coolant temperature rises above 95°C (203°F), the thermometer turns on and the electric cooling fan rotates.
4. With engine stopped - When the engine is stopped after high-speed operation, the vapor that is produced in the turbocharger cooling section transfers from the coolant flow tank to the reservoir tank where it condenses back into water. As the engine cools, the coolant flow tank then absorbs the water.

Scheme 3

WATER PUMP

The water pump is located on the left front portion of the cylinder block and is driven by the back side of the timing belt. Water inlet is located on the lower side of the water pump. The thermostat is built into the water inlet. When the impeller rotates, engine coolant is drawn into the water pump from the lower pipe via the thermostat (the lower pipe is connected to the radiator hose). It then flows along the perimeter of the impeller and is delivered to the engine's water passage. (Scheme 4)

The installation direction of the suction port on the thermostat housing differs between TURBO and Non-TURBO models.

Water Pump Seal

The mechanical seal has its seat pressed into the water pump shaft to form the seal and water pump as a single unit. With this design, the water pump cannot be disassembled. (Scheme 4)

Scheme 4

Scheme 5

THERMOSTAT

The thermostat is powered to open the valve by a totally enclosed wax pellet. The wax pellet expands with increased temperature and provides the sure open-close operation of the valve, and it features high durability. (Scheme 6)

Scheme 6

COOLANT FLOW TANK (TURBO)

The radiator is not equipped with a coolant flow cap. The coolant flow tank, which is located above the No. 4 cylinder, not only delivers coolant to the turbocharger, but also sends vapor produced in the turbocharger cooling section to the reservoir tank. This vapor condenses into water inside the reservoir tank and is then absorbed by the coolant flow tank.

Scheme 7

Scheme 8

Scheme 9

Scheme 10

Scheme 11

1. Installation is done in reverse order of removal procedure. Always use a new gasket.
2. After reinstalling the water pump, run engine to make sure that neither water leakage nor abnormal noise exists.

1. Remove the thermostat case cover and gasket, and pull out the thermostat.
2. Install the thermostat in the intake manifold, and install the thermostat cover together with a NEW gasket. The thermostat must be installed with the jiggle pin upward or facing front of engine.

Inspection

Replace the thermostat if the valve does not close completely at an ambient temperature or if the following test shows unsatisfactory results.

1. Immerse the thermostat and a thermometer in water. (Scheme 12) Raise water temperature gradually.
2. Measure the temperature and valve lift when the valve begins to open. Also measure when the valve is fully opened. See «THERMOSTAT SPECIFICATIONS»(/subaru/legacy/bcbjbf-1989-1994/remont/cooling-system-mechanical/#cooling-system-specifications-removal-installation).
3. Agitate the water during the test for even temperature distribution. Replace thermostat if not within specifications.

Scheme 12

THERMOSTAT SPECIFICATIONS

On-Vehicle Service

1. Remove radiator cap and top off radiator. Attach tester to radiator in place of cap.
2. Apply a pressure of 23 psi (157 kPa, 1.6 kg/cm 2 ) to radiator to check if the following occurs: Water leaks at/around radiator. Water leaks at/around hoses or connections.

Scheme 13

Scheme 14

Scheme 15

Scheme 16

Radiator Cap Inspection

1. Attach radiator cap to tester. Increase pressure until tester gauge pointer stops. (Scheme 17)
2. Radiator cap is functioning properly if it holds the service limit pressure for five to six seconds. See «RADIATOR CAP SPECIFICATIONS»(/subaru/legacy/bcbjbf-1989-1994/remont/cooling-system-mechanical/#cooling-system-specifications-removal-installation).

Scheme 17

RADIATOR CAP SPECIFICATIONS

Note. Remove all foreign matter and rust from cap; otherwise, pressure test results will be incorrect.

1. Disconnect ground cable from battery terminal.
2. Disconnect connector from fan motor.
3. Remove reservoir tank.
4. Loosen two bolts holding shroud to radiator underside.
5. Remove two bolts holding shroud to radiator upper side.
6. Remove radiator fan motor.
7. Remove fan motor from shroud. (Scheme 18)

Scheme 18

To install, reverse removal procedures. Observe the following items

1. Before installing cooling fan motor, apply a coat of sealant to threads and tighten nuts.
2. Ensure cooling fan does not come into contact with shroud when installed.
3. After installation, ensure there is no unusual noise or vibration when fan is rotated.

1. Remove hoses from coolant flow tank. (Scheme 19)
2. Remove the two bolts, and remove coolant flow tank.
3. Installation procedure is done in reverse order of removal procedure.

Scheme 19

Note. Coolant replacement interval is 30,000 miles or 30 months. Cooling system capacity includes heater and reserve tank.

Scheme 20

See also:
• THERMOSTAT SPECIFICATIONS