Features of the cooling system (VW Passat B4)

The engines use a liquid cooling system with forced circulation. The cooling system includes an aluminum radiator, expansion tank, water pump, thermostat and electric fan. The cooling system of cars equipped with air conditioning includes an additional fan (Fig. 2-29).



The radiator with aluminum fins is located at the front of the car.

Radiator length on cars with "EZ" engine is 430 mm. On cars with "RP", "RV" and "2E" engines it is 525 mm, on cars with air conditioning it is 720 mm. The temperature of the beginning of opening of the main thermostat valve is 85°C.

The full opening temperature of the main valve is 105°C.

The main valve piston stroke is 7 mm. The two-speed electric fan is switched on and off by a sensor installed on the left radiator tank. Brand and catalog number: Bosch 0 130 107 244.



Fan motor switch-on temperature,°C:

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

Fan motor switch-off temperature,°C:

• at 1st speed: 84-91;
• at 2nd speed: 91-98 (on the "AGG" engine with air conditioning: 88-91).

(The text is copied from this portal VWMANUAL)

Note. The electric fan power supply circuit includes a time relay that ensures its operation after the engine has stopped. The relay is activated by a temperature sensor installed in the radiator supply hose when the coolant temperature reaches 110°C.

The shaft of the centrifugal water pump is driven by the V-belt of the generator drive.

The size of the alternator drive belt for non-power steering is 9.5x950 mm, for power steering 9.5x730 mm.

Brand: Gates.

Belt tension is considered normal if the belt deflection when pressing hard with the thumb on the middle of the belt branch between the crankshaft and generator pulleys is within 10-15 mm. The opening pressure of the pressure reducing valve in the expansion tank plug is 1.2-1.5 kgf/cm².