Features of the cooling system (VW Passat B4)

The engines use a closed liquid cooling system with forced circulation. The cooling system includes a radiator, an expansion tank, an electric fan with two impellers, a centrifugal water pump and a thermostat. A plate aluminum radiator with plastic tanks is installed in the front of the car. A plastic expansion tank with transparent walls is installed in the engine compartment on the right.

The pressure of the safety valve in the tank cap is 1.2-1.5 kgf/cm². The AEG A465 electric fan has two impellers, one of which is mounted on the electric motor shaft, and the second is driven by the electric motor via a belt drive.

Electric motor start temperature:

• at 1st speed 92-97°C;
• at 2nd speed 99-105°C.

Electric motor switch-off temperature:

• at 1st speed 84-91°C;
• at 2nd speed 91-98°C.

Electric fans installed on "1Z" and "AFN" engines, depending on the configuration, are two- or three-speed.

Electric motor start temperature:

• at 1st speed 92-97°C;
• at 2nd speed 99-105°C;
• at 3rd speed 110-115°C.

Electric motor switch-off temperature:

• at 1st speed 84-91°C;
• at 2nd speed 88-91°C;
• at 3rd speed 105-110°C.

The thermostat is installed at the bottom of the water pump where the radiator inlet hose is connected. The temperature at which the main valve begins to open is 87°C. The temperature at which the main valve fully opens is 102°C.

The main valve piston stroke is 8 mm. The drive belt of the second impeller of the electric fan is of the brand and type Continental 2PJ 786. The water pump is located at the bottom of the cylinder block and is driven by the V-belt of the generator drive.



[The text is copied from this portal: vwmanual.ru]

Brand and type of alternator drive belts:

• cars with engines "1Y", "RA" and "SB": Continental FO-Z 9.5x950 La;
• cars with engines "AAZ", "1Z" and "AFN": Continental FOLaL 11.9x903 La SR.

Normal belt deflection when pressing with your thumb on the middle of the long branch of the belt:

• cars with engines "1Y", "RA" and "SB" 10 mm;
• cars with engine "AAZ", "1Z" and "AFN": new belt 2 mm, worn-in belt 5 mm.

The cooling system details are shown in Fig. 3-22.