Contents: Fan with viscous coupling ↡ Checking the fan with viscous…↡ Electric fan ↡ Checking the fan for proper operation ↡
The fan serves to increase the intensity of radiator cooling with air. The more intense the blowing, the more intense the heat exchange. Depending on the model and configuration, electric fans or fans with a viscous coupling are installed on the engines. Both types of fans are mounted directly in front of the radiator and are switched on as needed.
Fan with viscous coupling
Fig. 4.50. Viscous coupling in section: 1 – coupling body; 2 – housing cover; 3 – pressure washer; 4 – reserve cavity; 5 – working cavity; 6 – pin; 7 – bearing; 8 – bearing axis; 9 – gasket; 10 – bimetallic plates; 11 – valve
The viscous coupling (Fig. 4.50), filled with silicone oil, is located in the middle of the fan impeller and is controlled by bimetallic plates. There is a steel pin on the bimetallic plates, which at an ambient temperature of about +85°C opens the oil passage into the working cavity. The viscous silicone oil creates a force closure between the pulley and the fan, under the action of which the latter begins to drive air.
When the engine is cold, the clutch is practically disconnected - the oil is in the reserve cavity, so there is no energy consumption for ventilation. The fan speed remains below 1000 min⁻¹. It changes along with the engine speed, but only at low speeds. When 4500 min⁻¹ is reached, the safety valve is triggered, which limits the fan speed to around 3300 min⁻¹.
Checking the fan with viscous coupling
1. With the engine off, check that the fan moves easily.
2. Make sure that the fan does not have significant axial or radial play.
3. Make sure there are no traces of oil on the viscous coupling. If there is oil, it must be replaced.
4. With the engine warmed up and the hood closed, set the speed to 3000 min⁻¹.
Fig. 4.51. Viscous coupling: 1 – impeller; 2 – coupling body; 3 – impeller mounting bolts; 4 – bimetallic plates
5. The coupling (Fig. 4.51) should start working at a coolant temperature of +90...+95°C. Otherwise, replace the coupling.
Electric fan
An electric fan is installed only on 4-cylinder engines. The cooling system of a 4-cylinder engine is immediately "loaded" when the engine is idling or, for example, when driving in mountainous terrain. If the coolant temperature indicator light suddenly starts to light up periodically, this indicates a fan malfunction. In this case, you can continue driving to the repair site, after letting the engine cool down. In this case, the engine should not experience heavy loads and should idle as little as possible.
Caution! When the engine is stopped but still hot, do not keep your hands near the fan impeller! The fan may start working even when the ignition is off.
Checking the fan for proper operation
1. Check the fuse.
2. Disconnect the plug from the socket located next to the thermostat housing.
3. Short-circuit the plug with a wire. If the fan starts, the thermal switch is faulty. If it does not start, the fan is faulty or the cable is broken.
4. To continue driving, short-circuit the plug and insulate it. Also, to avoid short circuits and dirt ingress, insulate the mating part.
5. When stopping or parking for a long time, be sure to remove the jumper wire to avoid discharging the battery.