The cooling system of all Volkswagen Transporter T4 engines is liquid, closed, operating at elevated pressure. The fluid is driven by a vane-type centrifugal pump. The direction of fluid flow is controlled by a thermostat, depending on the temperature of the coolant. The radiator fans (there are two of them) are switched on by a two-mode thermal switch installed in the radiator. The fans are two-speed, the operation of the engine at temperatures from 84 to 90ºС is provided by the first medium-speed operation mode. At a coolant temperature of 93-98º, the fans of the T4 cooling system operate at full capacity. The cooling system has a separate expansion tank (see Fig. 227).

Rice. 227 Expansion tank

On four-cylinder engines, both fans in the Volkswagen T4 cooling system are driven by one electric motor (see Fig. 232).
For the rest of the engines - from two (one per impeller). Power is supplied to the electric motors regardless of the position of the key in the ignition, so be careful when working in the engine compartment. Diesel engine cooling systems are different. The differences between the cooling systems of four and five-cylinder engines are shown in fig. 228 and 229.

Rice.
228 The device of the cooling system of the four-cylinder engine T4 1 - expansion tank, 2 - radiator, 3 - cooling system pump, 4 - coolant drain plug, 5 - thermostat, 6 - cooling system pump, 7 - engine oil cooler, 8 - housing, 9 - block head, 10 - solenoid valve, 11 - interior heating control valve, 12 - additional heater, 13 - heater 1, 14 - heater 2, 15 - tee, a - upper coolant hose, c - lower coolant hose

Rice.
229 The device of the cooling system of the five-cylinder engine 2.4 l Volkswagen T4 1 - expansion tank, 2 - radiator, 3 - cooling system pump, 4 - coolant drain plug, 5 - thermostat, 6 - coolant pumps, 7 - housing, 8 - oil cooler, 9 - block head, 10 - solenoid valve, 11 - additional heater, 12 - interior heating control valve, 13-1 heat exchanger 14-2 heat exchanger, a - upper coolant hose, c - lower coolant hose

The steps below also apply to diesel engines. The cooling system pump of a four-cylinder diesel engine is removed and installed in the same way as in a gasoline engine.