Cooling System 4-CYL: Overview Saab 9-3 II

Description

The cooling system is the pressurized type with crossflow radiator and expansion tank. The cooling system includes engine oil cooling, turbocharger cooling and automatic transmission fluid cooling.

Scheme 1

The centrifugal coolant pump is located on the left-hand side of the 105 engine and is driven by the crankshaft via the balancer shaft chain circuit.

Scheme 2

The coolant pump sprocket also serves as an idler wheel for the balancer shaft chain. This is to get the balancer shafts to rotate in opposite directions.

Scheme 3

The traditional wax-type thermostat is located on the inlet side in a housing mounted on the left-hand side of the engine. The housing contains a blank plug that covers a hole where an electric block heater can be fitted. The thermostat is mounted on the return side of the coolant circuit, which helps heat the engine and reduces cyclic variations in the coolant temperature. It starts to open at 80°C and is fully open at 95°C. The opening stroke is 9 mm. The expansion tank is located on the left-hand side of the engine bay and is connected to the thermostat housing, to the top left of the radiator and to the highest point on the cylinder head. The latter connections are used to ventilate the cooling system. The coolant filler cap includes an integrated safety valve that opens at 1.4 bar. When the engine is turned off, the coolant in the turbocharger will circulate in the opposite direction than when the engine is running. This is achieved with the thermosiphon principle.

Scheme 4

The car is equipped with electric radiator fans that are located behind the radiator. These fans can be run at 4 different speeds and are controlled by ECM.

Scheme 5

Scheme 6

The car is equipped with two radiator fans located behind the radiator. The fans have 11 blades with diameter 320 mm and can be operated in four different stages depending on engine temperature and A/C pressure.

ENGINE TEMPERATURE

The radiator fans have their own relay box and communication between ECM and the radiator fan relay box is achieved through a cable via UEC.

The fans are controlled by ECM through the following input signals

1. Coolant temperature
2. A/C pressure
3. Fluid temperature from automatic transmission

Scheme 7

Scheme 8

Radiator fan relay box (706) is supplied with +30 from UEC to pins 3 and 6, and is grounded to G30A from pins 5 and 2.

From ECM come 3 cables via the underhood electrical center to the relay box. These cables are connected to pins 1, 4 and 7 on the relay box. Depending on the connection being grounded and the combination in which they are grounded, four different speed stages can be obtained for the radiator fans.

The radiator fans start in the following cases

Scheme 9

1. Temperature logic: Stage 1 on the radiator fans starts when the coolant temperature has reached 100°C and stops when the temperature has dropped to 96°C. Stage 2 on the radiator fans starts when the coolant temperature has reached 108°C and returns to stage 1 at 104°C. Stage 3 on the radiator fans starts when the coolant temperature has reached 114°C and returns to stage 2 at 110°C. Stage 4 on the radiator fans starts when the coolant temperature has reached 120°C and returns to stage 3 at 116°C.
2. A/C pressure logic Stage 1 on the radiator fans starts at an A/C pressure over 1100 kPa and stops at a pressure below 800 kPa. Stage 2 on the radiator fans starts at an A/C pressure over 1700 kPa and returns to stage 1 at a pressure of 1400 kPa. Stage 3 on the radiator fans starts at an A/C pressure over 2000 kPa and returns to stage 2 at a pressure of 1800 kPa. Stage 4 on the radiator fans starts at an A/C pressure over 2300 kPa and returns to stage 3 at a pressure of 2100 kPa. If the automatic transmission fluid temperature rises to 140 C, the radiator fans will start at stage 4 irrespective of the temperature of the engine and the pressure in the A/C system. Once the transmission temperature has dropped to 130 C, the radiator fans will return to normal logic. If the temperature signal is missing, the radiator fans will run constantly at full speed, i.e. stage 4.

Scheme 10

With the ignition switch turned to ON, ECM will use the following information on the bus

1. Coolant temperature (bus from ECM)
2. A/C pressure
3. A/C system status (active/inactive)
4. Transmission temperature

This information is used by ECM to control starting and stopping the radiator fans.

Operation With Ignition OFF

ECM controls the fans when the ignition is "OFF" depending on the engine temperature. If the temperature is below 100 degrees, they will not be turned on but if the temperature exceeds

100°C, the radiator fans will keep running for 30 seconds

105°C, the radiator fans will keep running for 90 seconds

110°C, the radiator fans will keep running for 150 seconds

115°C, the radiator fans will keep running for 210 seconds

120°C, the radiator fans will keep running for 270 seconds

The radiator fans then run in "Stage 1" and the temperature will be measured again every 30 seconds.

Note that only "Stage 1" is active with the ignition OFF.

Scheme 11

The coolant temperature gauge provides the driver with information on the engine coolant temperature.

The coolant temperature gauge is supplied with current and controlled from the main instrument unit.

The engine control module sends continuous information on the bus concerning the coolant temperature.

The coolant temperature gauge is divided into 5 fixed break points. The main instrument unit is programmed to move the gauge needle to the fixed break points at specific temperatures in order to provide a stable display at normal coolant temperatures.

The following break points are programmed in the main instrument unit (factory setting)

COOLANT TEMPERATURE

See also:
• HORN