General information (Opel Astra H)

Engine cooling system

1. All models of the vehicles considered in this Manual are equipped with a positive pressure engine cooling system with thermostatic control of the working fluid circulation. The fluid circulation is provided by a water pump, which is permanently operating during engine operation and is fixed to the engine block. The pump is driven by a multi-rib or toothed belt, depending on the engine model. The fluid flow washes the areas where each cylinder is located in the block, after which it is directed to the rear of the engine. Cooling channels laid in the block and cylinder head casting provide intensive cooling of the intake and exhaust ports, spark plug installation areas and exhaust valve guides.

2. The cooling system can operate in one of three modes. In the first stage, when the engine is started, until the coolant temperature rises above a certain value, the coolant circulates in a small circuit, from which the radiator is excluded. As the liquid warms up, the valve of the thermostat included in the system tract opens and the radiator is included in the circulation circuit. The liquid passes through the radiator from top to bottom and is cooled as a result of outside air blowing on the radiator fins. The location of the cooling system hoses is shown in the accompanying illustration. When the car is constantly moving at medium and high speeds, as a rule, the oncoming air flow is sufficient for normal cooling of the liquid. With a certain increase in engine speed, as well as when the coolant temperature reaches the next control value, the adjustable electric fan of the cooling system is activated. The additional air flow pumped by it significantly increases the efficiency of the radiator heat exchanger. The moment of switching on the fan and the number of its revolutions are determined by the engine control unit (ECM) using data received from the coolant temperature sensor. The fan is switched on via one or more relays. Depending on the engine type and configuration, 1 or 2 fans can be installed on the vehicle.





3. The cooling system has a sealed design and is tightly closed with an expansion tank cap capable of withstanding a certain excess pressure (1.2-1.5 bar), which increases the boiling point of the coolant and, accordingly, the efficiency of heat removal through the radiator. A decrease in the boiling point can lead to the formation of stagnation zones, which reduces the efficiency of engine cooling. For this reason, the cooling system must be filled with a coolant of the appropriate composition all year round. When the internal pressure in the system exceeds a certain value, excess coolant flows through the connecting (overflow) hose into the expansion tank. As the system cools, the liquid automatically returns from the tank to the radiator.



4. Add coolant to the system through the neck of the expansion tank (see Chapter 1), which simultaneously also acts as a receiver, accumulating the excess liquid displaced from the radiator.

5. Due to the listed design features, such a cooling system is called closed, since any functional losses of the working fluid are excluded.

Interior heating, ventilation and air conditioning (HVAC) systems

Heating and ventilation system

6. The main components of the interior heating system (see accompanying illustrations) are an electric fan with several speed modes and a heat exchanger placed in a box-shaped heater casing, fixed under the car dashboard. The heat exchanger is connected to the engine cooling system by means of hoses. The control unit for the heater/air conditioner is mounted in the car dashboard. The coolant heated in the engine circulates through the heater heat exchanger, giving off its heat to the air filling the casing. When the interior heating is turned on, the plate damper opens, as a result of which the internal volume of the heater casing is connected with the volume of the interior. When the fan is turned on, the impeller of the latter begins to drive the air supplied to the interior through the heat exchanger, providing its intensive heating. Air leaves the interior through the ventilation openings in the rear of the car.





7. Air is supplied to the passenger compartment through the face-level deflectors, footwell nozzles and windshield blower deflectors. Before air enters the passenger compartment, it is cleaned by a dust-catching filter. The air flow distribution diagram is shown in the accompanying illustration.





8. If the vehicle is equipped with a diesel engine, an additional electric heating element can be installed to heat the air entering the passenger compartment. The electric heater is installed next to the heat exchanger. After the engine is started, the element heats up and gives off heat to the cold air passing through - the degree of heating depends on the outside air temperature.

9. Messages about malfunctions in HVAC systems are recorded in the ECM electronic memory unit and can be read by connecting a special scanner - accurate diagnostics without the above device is impossible.

10. The rules for using the controls for the operation of HVAC systems are described in detail in the Chapter "Controls and Operating Techniques".

Attention: If, as part of the work on the heater, work is also carried out on electrical equipment, it is necessary to disconnect the battery (see Chapter 5).

Air conditioning system (A/C)

11. At the owner's request, the car can be equipped with an air conditioner. The air conditioner is installed as a single system with the heating system and together with it ensures the maintenance of the set air temperature in the cabin.

12. The air conditioning system includes a condenser installed on the cooling system radiator (see illustration 1.12a), located next to the heater heat exchanger, an evaporator, a compressor mounted on the engine block, and a receiver-dryer (battery), equipped with a high-pressure reducing valve. All components are interconnected by refrigeration lines (see illustration 1.12b). The compressor is driven from the crankshaft by means of a multi-rib belt.





13. The operating principle of the air conditioning system is shown schematically in the accompanying illustration. In cooling mode, the air conditioner operates on the principle of a refrigerator: the compressor compresses the gaseous refrigerant (R 134 A, freon-free), whereupon the refrigerant heats up and is directed to the condenser, where it cools and liquefies. Passing through the expansion valve, the refrigerant expands and enters the evaporator, turning into steam - a process accompanied by strong heat absorption.





14. The fan drives the air entering the passenger compartment through the evaporator heat exchanger. As a result of the evaporation and cooling of the refrigerant, the heat of the air flowing around the evaporator is absorbed. The air is cooled and the resulting moisture turns into condensate, which is directed outside the passenger compartment. The intensity of the cooling process depends on the set temperature and the setting of the fan switch.



15. At the user's request, the air conditioning system can be switched off, which switches off the compressor, and in vehicles with a diesel engine, the additional heating element is also switched off – which significantly reduces fuel consumption.

16. An HVAC system with automatic temperature control can be installed as an option (climate control). The automatic operation mode ensures that a constant temperature selected by the user is maintained in the passenger compartment and dehumidifies the air entering the passenger compartment. In addition, the amount and distribution of air supplied to the passenger compartment are automatically adjusted, and fluctuations in outside temperature are compensated. When the economical mode (ECO) is activated, the air conditioner is switched off, but the heating and ventilation systems continue to operate in automatic mode.

17. The rules for using the controls for the operation of heating, ventilation and air conditioning systems are described in detail in Chapter "Controls and operating techniques".

18. Lubrication of the moving parts of the air conditioning system is provided by the components contained in the refrigerant and its regular circulation, which prevents the formation of pores in the seals and the occurrence of corrosion. Therefore, even if there is no need to use the air conditioner, especially in the cold season, it should be turned on at least once a month for a short time at the highest power. Turning on should be done at a uniform speed of the car and with a warmed-up engine.

Warning: Air conditioning work should only be performed by service station specialists. For this reason, air conditioning repair is not described here! Do not open the refrigerant circulation circuit, since the refrigerant may cause frostbite if it comes into contact with the skin!

Safety precautions when servicing the air conditioning system

The A/C system must be serviced only by trained technical personnel who are trained in safe operation techniques, proper equipment, and depressurization procedures, as well as familiar with the methods of collecting and storing automotive refrigerant.

• Avoid contact of refrigerant with skin;
• Wear safety glasses when working near the A/C system;
• If refrigerant gets on your skin or in your eyes, do not rub the affected area. Immediately rinse the affected area with cold water for at least 15 minutes. Immediately seek medical attention at a medical facility. Self-medication is not allowed;
• The refrigerant is stored in cylinders under pressure. Store the cylinder at a temperature not exceeding +50 degrees. Take measures to prevent the cylinder from falling from a height or other situations that may lead to its damage;
• Work should be carried out in a well-ventilated area. The refrigerant evaporates quickly, reducing oxygen supply and making breathing difficult;
• The gaseous refrigerant is heavier than air and should collect relatively quickly at a low level, such as under a car;
• When refrigerant burns, toxic gas is formed. Keep refrigerant away from open sources of fire. Do not smoke when working on the A/C system;
• When welding near the A/C system, do not expose it to high temperatures or open flames. Overheating may cause the system to become pressurized and ignite;
• Cleaning the condenser or evaporator with water vapor is not permitted. Only cold water or compressed air should be used.