Cooling System Component Removal & Installation: Other Subaru Outback BG

COOLANT FLOW

This cooling system operates in three steps, depending on temperature of the coolant that is flowing through the cooling circuit. (Scheme 18)

Scheme 18

1. Thermostat Closed - When coolant temperature is below 169°F (76°C), the thermostat remains closed and the coolant flows through the bypass and heater circuits. This permits the engine to quickly warm up.
2. Thermostat Open - When coolant temperature is above 169-176°F (76-80°C), the thermostat opens and the coolant flows through the radiator where it is cooled.
3. Electric Cooling Fan Operating - When coolant temperature rises above 203°F (95°C), the ECM receives a signal from the engine coolant temperature sensor. The ECM then sends an ON signal to the radiator fan to rotate.

WATER PUMP

Note. Water pump is also referred to as engine coolant pump.

The water pump is located on the left front portion of the cylinder block and is driven by the timing belt. The thermostat is built into the engine coolant inlet which is located on the lower side of the water pump. 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 engine coolant passage. (Scheme 19)

Scheme 19

Water Pump Mechanical 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 20)

Scheme 20

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 21)

Scheme 21

ENGINE COOLANT TEMPERATURE SENSOR

The engine coolant temperature sensor (thermostat) is located on the engine coolant pipe; the pipe is made of aluminum alloy. The sensor's thermistor changes resistance with respect to temperature. The engine coolant temperature signal converts into resistance then is transmitted to the ECM. (Scheme 22)

Scheme 22

RADIATOR FAN

The radiator fan is plastic. It is installed in the electric motor and is located on the radiator shroud. (Scheme 23) Vehicles equipped with A/C have both a radiator main fan and a radiator sub fan. Vehicles without A/C are equipped with only a radiator main fan.

Scheme 23

Scheme 24

Scheme 25

Scheme 26

Scheme 27

Scheme 28

Scheme 29

Scheme 30

1. Lift vehicle.
2. Fit vinyl tube to drain pipe. (Scheme 29)
3. Remove radiator cap to drain engine coolant faster. Loosen drain cock to drain engine coolant into a container.
4. Remove air vent plug from radiator. (Scheme 30)
5. Fill engine coolant up to filler neck position of radiator.
6. Fill engine coolant to upper level (full line) of reservoir tank.
7. Close both the radiator cap and the reservoir tank cap properly.
8. Reinstall air vent plug.
9. Run engine for more than five minutes at 2000 to 3000 RPM, until engine is completely warm.
10. Stop engine. Before inspecting fluids, allow temperature to drop to a safe level and perform the following procedure: Add engine coolant to filler neck position if levels have dropped in the radiator. Add engine coolant to upper level (full line) if levels have dropped in the reservoir tank. Close both the radiator cap and the reservoir tank cap properly.

RADIATOR CAP

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

Scheme 31

1. Attach radiator cap to tester.
2. Increase pressure until tester gauge pointer stops. Radiator cap is functioning properly if it holds the service limit pressure for 5-6 seconds. (Scheme 31)

RADIATOR CAP SPECIFICATIONS

RADIATOR FAN & FAN MOTOR

For radiator fan removal and installation procedure, see appropriate ELECTRIC COOLING FANS article.

Scheme 32

1. Drain engine coolant. Set container under vehicle and drain cock from radiator. See «DRAINING & REFILLING COOLING SYSTEM»(ref-157727-S32284355912003082300000).
2. Disconnect radiator outlet hose from thermostat cover. (Scheme 32)
3. Remove thermostat cover and gasket, then pull out the thermostat.
4. Install the thermostat in the intake manifold, and install the thermostat cover together with a gasket.
5. Position jiggle pin of thermostat to front side.
6. Fill and bleed air from cooling system. See «DRAINING & REFILLING COOLING SYSTEM»(ref-157727-S32284355912003082300000).

Water pump is driven by timing belt. For timing belt removal and installation procedures, see

1. «1.8L & 2.2L 4-CYL»(ref-49461) article in ENGINE, or
2. «2.5L DOHC 4-CYLINDER»(ref-49462) article in ENGINE